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Old 06-01-2015, 08:47 PM
leathermech leathermech is offline
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Default 38 Special pressure signs

Iím asking the question now because Iíve never thought to ask it. ďWhat pressure signs?Ē

While browsing a forum discussing working up loads for the 38 Special, talk turned to Keithís published loads, as it usually does. One feller mentioned, pressure was fine because the cases dropped from the cylinder easily. Another pal fired back how thatís not the only or the most relevant (paraphrasing) pressure sign. He continued to stress that the feller was foolhardy and a missing digit waiting to happen (again, my words).

Hereís what Iím thinking. The 38 Special was worked up to pressures sufficient to blow up anything but a heavy duty and cases still slipped from the cylinders. We take that same cartridge in a slightly longer case and call it the 357 Magnum, and except for nice, flattened primers, there are no signs of pressure. Iíve loaded 38 Special to magnum ranges (replicating Elmerís 358421 loads) with no problem in my 686. I read that to mean, essentially the same case can range pressures from 17K to 40K but in the wrong gat, the first observable sign of over pressure might very well be a top strap launched into orbit.

Before you hit your reply button, please accept that Iím not suggesting the Special and Magnum are interchangeable. No sir, not at all. What I am suggesting is an adventurous soul could easily stoke his 38 Special up to 357 Magnum pressure with no signs of danger. The feller in the post wasnít so wrong by citing his cases slipping from the wheel. Rather, he was risky by (maybe) stepping out on his published max limits because you can slip right through the Special range, skip past all the plusses and Pís to land in magnum range without observing the pressure signs depicted in a loading manual. The specials are easily wolves in sheepís cylinders and I think the pal missed the lesson.

What pressure signs?? Thoughts?
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Old 06-01-2015, 09:50 PM
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What I watch for is "cratering" of the primer when the excess pressure caused it to flow around the firing pin. The tell tale raised edge around the primer hit forms the "crater".



Admittedly, I do NOT load hot revolver loads, so there will undoubtedly be other more useful replies from the guys who do.

Hope this helps, or at least sparks some more knowledgeable comments.
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Old 06-01-2015, 09:57 PM
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Forget looking for "Pressure signs" with .38 Special, or any low pressure cartridge! You simply are not going to see any because nothing will show, absolutely nothing, until pressure levels are 200% or more of allowable limits. Think about .357 Magnum that operates in the range of 35,000 PSIG. Rarely will you see any of the usual "Pressure signs" even at this level, and .357 is nothing more nor less than .38 Spl. in a slightly longer case at an increased pressure level.

You may see pressure signs in the Magnums, .40 S&W, 10mm, .38 Super and similar high-intensity cartridges, but even then rarely. The most common "Pressure sign" you will see in any handgun is when pieces of the gun suddenly become detached from the frame of the gun, commonly referred to as a "Kaboom", or KB.

pressure signs are strictly a phenomenon related to high-pressure rifle cartridges, those normally operating in excess of 50,000, and even then usually only once even this level has been significantly exceeded!
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Old 06-01-2015, 10:08 PM
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Default Nothing is certain here......

You can watch for primer flattening and piecing and if the cases won't eject easily, but there really aren't any really reliable signs of overpressure in .38 special and similar type cartridges short of blowing up the gun. Keep within published data. Some guns may not like max or near max loads.
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Old 06-01-2015, 10:33 PM
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If you have a recent Speer manual read the section on pressure. There
is a good explanation of why you can't read pressures of low power
handgun cartridges by visual indicators. Some primers are softer than
others and may show cratering at normal magnum handgun pressure
levels and do not indicate excessive pressure. The advice to "work up
slowly while watching carefully for signs of excessive pressure" gets
repeated endlessly when working with cartridges that operate at
15,000 psi or so and is meaningless. Sticking to published data is the
best way to avoid trouble unless you feel like you have enough
experience to work up safe loads.
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Old 06-01-2015, 10:39 PM
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Though I have never tested the idea of over-pressure, in .38 Special, or any other pistol cartridge, I have often wondered how over-pressure would be detectable in a (relatively) low-pressure cartridge. I know what to look for. I've seen signs of over-pressure in rifle cartridges. I just can't ever remember seeing the signs in any pistol cartridge. When I work up a load, I always look for the signs. Mostly out of habit, I think. Just have never seen 'em.
One anecdote, here. At one time, I had a Colt Trooper Mk III. They were notorious for having "tight" cylinders. One day, I was shooting some light HBWC target loads. Even with that light load the spent cases were difficult to get out, sometimes. I occasionally had to tap on the eject rod to get the cases out. Some guy saw me doing that, and he moved a couple tables further over. Guess he thought that tight cases meant hot load.
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Old 06-01-2015, 10:49 PM
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As others have noted, the .357 magnum operates at 35,000 psi, in brass that has the same web as the shorter .38 Special. You're not going to see any signs of excess pressure even in 23,000 psi "+P+" loads.

Take a look at .38-44 load data as some of them ran as high as 30,000 psi - in large frame revolvers designed for that pressure. Those loads are what led to the development of the .357 magnum, and the much higher pressure is why the .357 mag was made 1/8" longer.

Like the earlier .38-44 loads, the law enforcement only "+P+" loads in the 1970s were shot in revolvers designed for the .357 Magnum and were never intended for the average .38 Special.

What you'll eventually see if you shoot those kinds of loads in a J-frame or a non Model 19 K frame will be some serious loosening of the revolver.

----

.38 Special is one of those rounds where you want to a) stick with published load data, and ideally b) use a chronograph to ensure you're getting the velocities you expect from the load. If you've got excessive velocity for the barrel length, then you've also most likely got excessive pressure and should back the load off a bit.
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Old 06-01-2015, 10:57 PM
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Default Chronograph

While over pressure signs can be misleading or non existent there is one sure way to find out.

You must chronograph your loads. The velocity reading will be the best way to find out if you're exceeding the working parameters of the cartridge.

When your .38 Special loads are clocking as fast as the known velocity of the .357 then you know that the pressure is too high.

Anything else is just guess work based on observations of fired cases.

BLM
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Old 06-01-2015, 11:16 PM
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There is an approximate correlation between MV and peak chamber pressure, but that is affected somewhat by the propellant used, and is not very reliable. Extreme overpressure will cause expansion of the cartridge case head diameter, i.e., the area just ahead of the rim or extraction groove. But when you see an increase in diameter, you've already gone too far. I won't go into detail, but I once had a project to develop some 5.56mm loads, and I had no other way to judge excessive chamber pressure than to measure the head diameters with a digital caliper before and after firing. When it increased more than about 0.002", I stopped. Judging pressure from primer appearance is very imprecise and unreliable, except if you see primer flattening and firing pin cratering, you know it's a hot load. If the primer blows out of the pocket, you know it's really hot.
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Old 06-02-2015, 01:08 AM
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The 38 special case can go way overboard with higher fps and
still not show high pressures.

I tested full 38 loads in my "L" frame 686 357 magnum and
logged the fps . I then added more powder to three bullets.

A 158 XTP went from 832 to 979 fps. ( fast powder )
A 158 lead went from 909 to 1024 fps. ( med. fast )
A 110 XTP went from 1080 to 1305 fps. ( med powder )

These had pressure signs in the Magnum.............
I would hate to see what would happen if they ended up in even
a STEEL J frame with a mag frame, if someone let it happen.

I never load a 38 special more than a "Standard Pressure" loading
if the case does not have a +P stamp on it.

Too many standard 38's in my family ..... and any +P loads are well marked
and kept separated from the standard ammo.

Full loads are fun now and then but 98% of our shooting is with
target or standard loads, which lets us shoot more without hitting the asprin bottle.

Good shooting.
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Old 06-02-2015, 02:07 AM
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Quote:
Originally Posted by leathermech View Post
I’ve loaded 38 Special to magnum ranges (replicating Elmer’s 358421 loads) with no problem in my 686. I read that to mean, essentially the same case can range pressures from 17K to 40K but in the wrong gat, the first observable sign of over pressure might very well be a top strap launched into orbit.
My thought on this, like Nevada Ed mentioned, is that 38 Special cases come in various strengths. You don't want to use a "wadcutter" case for hot loads as it's far weaker. And you wouldn't want a "hot" loaded 38 Special to accidentally get in a non-magnum gun.

I have a bucket of 38 Special brass that I just don't care to load anymore for my 357 Mags choosing to use only 357 cases for light to magnum loads. Sure, you can hot load the right 38 Spcl. case but why? Just buy 357 Mag brass & have a blast, safely.

.
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Old 06-02-2015, 08:09 PM
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Bruce Lee has the most practical suggestion. While pressure and velocity may not correspond directly finding that a load you've worked up that produces 1100 fps with a 125 grain bullet from a 4 inch revolver is a pretty darned good hint that you are way over the recommended pressure for the 38 special. In fact that's a load result pretty typical for a mid range 9mm parabellum, so it wouldn't be too difficult to conclude pressure somewhere around 27-30,000 psi.
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Old 06-02-2015, 10:22 PM
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Quote:
Originally Posted by Nevada Ed View Post
I never load a 38 special more than a "Standard Pressure" loading
if the case does not have a +P stamp on it.

Too many standard 38's in my family ..... and any +P loads are well marked and kept separated from the standard ammo.
I take it a step farther and only load "+P" loads in nickel plated brass.

The nickel plated case makes the +P loads instantly identifiable and I never put a load with a nickel plated case in any of my standard pressure .38s.
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Old 06-03-2015, 05:55 AM
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As someone else already mentioned, a chronograph is a great tool to use for working up loads. I try to stick within published data, but I also use my chronograph and closely observe fired cases, as well as how the gun reacts while working up loads. Unfortunately, with plated bullets there's still a severe lack of published data so a chronograph is indispensable in cases such as these as anything else is just a complete shot in the dark. Chronographs are something that may sit around not being used most of the time, but they sure are nice to have on hand when you get the itch to experiment. Sometimes we drop $100 on a nice new set of dies and shell holder but never get around to dropping the same amount on such a useful tool.
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Old 06-03-2015, 10:04 PM
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Quote:
Originally Posted by Bruce Lee M View Post
While over pressure signs can be misleading or non existent there is one sure way to find out.

You must chronograph your loads. The velocity reading will be the best way to find out if you're exceeding the working parameters of the cartridge.

When your .38 Special loads are clocking as fast as the known velocity of the .357 then you know that the pressure is too high.

Anything else is just guess work based on observations of fired cases.

BLM

Measuring velocity is good, but not a tell-all. , The two don't necessarily have a linear relationship.

If you're wanting to duplicate some Keith loads, I suggest they only be used in .357s,

I've shot Skeeter Skeltons load quite a bit. It's basically a magnum in a .38 special case, but only for use in a .357.

I did flatten primers once in a .357 using a max charge of 296 (per the Speer manual of the day, which said don't reduce a ball powder load.). The report sounded like a high-power rifle.

BTW, extraction was still easy.
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Old 06-03-2015, 11:39 PM
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Quote:
Originally Posted by jtcarm View Post
Measuring velocity is good, but not a tell-all. , The two don't necessarily have a linear relationship...
Can you elaborate on this? Seems to me increasing pressure would pretty much have to correlate to increasing velocity - and vice versa. How could it not?
If I can't rely on loads falling within standard velocity ranges as an assurance that my loads are withing acceptable pressure limits, what the HECK can I use as a "measuring stick" to ensure safety?
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Old 06-04-2015, 04:09 AM
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Is velocity always going to point to higher pressures? If so how do some companies get more velocity from a round and still claim "normal" or non +p pressures.

Something seems hokey with this.
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Old 06-04-2015, 09:19 AM
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There is a direct correlation between velocities and pressures - BUT . . . the only criteria for demonstrating this is to use the exact same loading techniques, bullet, primer, crimp, and brass, and as you increase the volume of the same powder, you will see a direct linear increase in pressure and velocity. Change any of these variables and there is no way to gauge the pressure effects by velocities alone. Random experimentation will result in having no idea of what pressures you are working with, so stick with the reloading manuals, since those loads have been pressure tested.

A great example is to think about proof testing by arms manufacturers. Shotgun companies often test with a 2X max-pressure proof load and the shotgun shell looks exactly like any low pressure target round.

I do not think there are any 100% reliable ways to visually determine over-pressure loads without physically measuring it as you shoot. Hardly anyone has the equipment or capability to do that.
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Old 06-04-2015, 10:17 AM
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Quote:
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Can you elaborate on this? Seems to me increasing pressure would pretty much have to correlate to increasing velocity - and vice versa. How could it not?
If I can't rely on loads falling within standard velocity ranges as an assurance that my loads are withing acceptable pressure limits, what the HECK can I use as a "measuring stick" to ensure safety?
Pressure is what creates velocity, so the relationship is very direct. However, even when average pressure and average velocity is within acceptable limits, the variation from shot to shot can become so large that some shots may be well above the maximum average pressure for a cartridge.

Assuming the loading techniques (crimp, seating depth, primers, charge weights, etc) are consistent, and the components are consistent (bullet weight, bullet diameter, case volume, etc) the pressure versus velocity curve will be fairly linear.

But even with all of the above consistencies you can encounter some areas where things start coming off the rails is in terms of excessively high standard deviations in velocity, which in turn reflect excessively high variations in pressure.

In some cases, that can be caused by a light load, where the low load density causes inconsistent ignition and pressure spikes. Your sign that you are getting into this territory is an increase in SD as the charge weights are reduced on the ladder.

For this reason, when I'm developing a light load, I'll start in the middle of the load data and work down.

The same increase in SD can begin to occur at the upper end of the scale, and it can result in some rounds having excessively high pressures, even when the average pressure is within the normal limits. Any inconsistencies in components just exacerbates this increased variability in pressure.

----

In short, you need to be looking not only at the average velocity, but also the standard deviation in velocity and understand what those numbers mean.
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Old 06-04-2015, 08:09 PM
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Quote:
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There is a direct correlation between velocities and pressures - BUT . . . the only criteria for demonstrating this is to use the exact same loading techniques, bullet, primer, crimp, and brass, and as you increase the volume of the same powder, you will see a direct linear increase in pressure and velocity.
I doubt they are linear. If the pressure doubled, I doubt the velocity would double. Because the more the pressure gets the bullet moving, the sooner it is out of the barrel and the less time that pressure is acting on it. Double pressure for the same amount of time might double the speed (though friction isn't linear either), but when the distance and not the time is fixed, they won't have a linear correlation.

That said, there is a correlation, and chronographing is all most of us can do.

But say I had a book load that claimed to be 30,000 psi and resulted in 1000 fps from my gun. If I felt my robust gun was safe with 40,000 psi loads, a linear relationship would suggest I keep loading more powder until it hits 1,333 fps. However, I tend to think this would be a bad idea and that with most powders it would result in a pressure higher than my target.
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Old 06-04-2015, 08:21 PM
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A relationship may exist, but the units of measure are different in pressure and velocity. One is in force per area, the other is in in distance per time.

So, it is clear that the pressure curve over time may provide some insight to the velocity.

Let me be simple and clear.. The instantaneous pressure will create velocity, but may exceed your maximus.

That pressure expended consistently over the time the projectile is traveling in the barrel, may decrease the maximum pressure while increasing the velocity.

It's hard to compare pressure units with velocity units.

But then again, I should be mowing the lawn.

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Old 06-04-2015, 08:29 PM
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High pressure "signs", especially in handgun rounds are like the "idiot lights" on the dashboard of my 1968 Malibu, when you see the light, the car is already overheated. Same as in 38 special, when you see a "sign" it's already too hot.
People who keep adding powder until they see a "sign" are pushing the envelope.
I have Elmer's book, Sixguns, and he had no way to measure pressure, was loading until he saw a sign and blew more than one sixgun apart, the 45 Colt SAA came apart to the extent that he stopped hot loading it and started experimenting with the S&W in 44 Special. From that , the 44 magnum was derived.
If the Colt SAA had stood up to Elmer's hot loadings , maybe Dirty Harry would have had a 45 magnum!
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Old 06-04-2015, 09:12 PM
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Quote:
Originally Posted by BC38 View Post
what the HECK can I use as a "measuring stick" to ensure safety?

In a word, caution.

Stick with mfr published data.

Don't try to emulate Elmer Keith's loads,

If you must, do it in a .357

If you want to know the pressure of your loads, send some to a ballistics lab.

I said "not necessarily" I didn't say they never correlate.

A better way of stating it is that it's not a one-to-one relationship

A 20% bump in pressure doesn't automatically mean 20% increase in velocity.

One of Elmer Keith's earliest published pieces was a letter to American Rifleman describing how he blew up a Colt SAA .45. IIRC the story was written by John Taffin and was what lead Keith to the .44 Special.

In an article about loading the .44 Special, the late (and great) John Wooters said he knew of three Colt SAA .44 Specials who had their top straps lifted by Keith loads.

No reason to blow up a perfectly good .38 or .44 Special when you can shoot a .357 or .44 magnum.
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Old 06-04-2015, 11:05 PM
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[QUOTE=BC38;138564553]Can you elaborate on this? Seems to me increasing pressure would pretty much have to correlate to increasing velocity - and vice versa. How could it not?

Trying to avoid all the linear correlation that has been stated here I will answer this one question only.

Increasing pressure does increase velocity to a point. The problem is when additional powder causes additional pressure without a significant gain in velocity.

Each powder has its own working parameters or the load range where it performs the best.

That is why we use 231 or Bullseye for light target loads. Unique, AA5 or similar powders for medium loads. And 2400,AA#9 or H110 for full power magnum loads.

The slower powders will give the most velocity at safe pressures with some exceptions.

A magnum powder such as Bluedot is wasted in a .38 Special case as are most of the slow burning powders are made for magnum loads.

The light target and medium powders tend to be the best to use in the .38 Special.

To learn more get and read published reload books and articles.

There is a wealth of data and information available besides all the well seasoned reloaders on a public forum.

BLM

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Old 06-05-2015, 02:10 AM
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The problem with "publishers data" is that many of the publishers have differing data.

Then you go the the powder website and that data differs as well.

and then you read older books and the data is much higher. Which begs the question: "Was it too hot back then? Or do we have lawyers covering load data now?"

Nobody wants to blow up their gun. But I (and others) would like to see what a 38 special can do....experiment. Maybe not to an Elmer Keith level, but you get the point.
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Old 06-05-2015, 07:38 AM
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I believe that different companies load data would become uniform if they could all agree what length barrel and bullet they were using. That is never going to happen. We need one independent company to test all powders and publish a book we all would probably buy. Anyone looking to start said company it could be fun. Don
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Old 06-05-2015, 10:21 AM
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Model 14: 38SPL.
Model 19: 357 Mag.

Both K frames.

Unless the metallurgy is different in cylinder and frame…. The difference is in case capacity.

Last edited by Bob T; 06-05-2015 at 04:46 PM.
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Old 06-06-2015, 04:15 AM
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Originally Posted by Kaedan View Post
The problem with "publishers data" is that many of the publishers have differing data.

Then you go the the powder website and that data differs as well.

and then you read older books and the data is much higher. Which begs the question: "Was it too hot back then? Or do we have lawyers covering load data now?"

Nobody wants to blow up their gun. But I (and others) would like to see what a 38 special can do....experiment. Maybe not to an Elmer Keith level, but you get the point.
You can experiment all you want, nobody's stopping you and
if your gun has the same metalurgy as a 357 then you might
be able to push pressures to 357 levels without blowing up
your gun. But you are still working with less case capacity so
357 velocities cannot be achieved at 357 pressures. But in
such experimenting you bear full responsibility for the
outcome. Expecting manual publishers and powder companys
to provide load data for such ventures is ludicrous. Published
data will vary between sources but will generally conform to
industry standards. I have older manuals dating back to the
60s and I don't see the "much higher" listed loads you refer
to. I have seen a few published loads that were fairly warm
with a notation that the loads were already used extensively
by handloaders. Like minded experimenters on the good old
net might be your best source for data.
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Old 06-07-2015, 10:43 AM
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You can experiment all you want, nobody's stopping you and
if your gun has the same metalurgy as a 357 then you might
be able to push pressures to 357 levels without blowing up
your gun. But you are still working with less case capacity so
357 velocities cannot be achieved at 357 pressures. But in
such experimenting you bear full responsibility for the
outcome. Expecting manual publishers and powder companys
to provide load data for such ventures is ludicrous. Published
data will vary between sources but will generally conform to
industry standards. I have older manuals dating back to the
60s and I don't see the "much higher" listed loads you refer
to. I have seen a few published loads that were fairly warm
with a notation that the loads were already used extensively
by handloaders. Like minded experimenters on the good old
net might be your best source for data.
It's funny because I have a speer manual that is brand new, and I bought one of those little booklets from cabelas that have data from numerous sources, and the data between the two is all over the place. Is one of them wrong? Is one of them being careless, or the other one being cautious? It just would be nice to know. Bummer that there are no pressure signs in such a little pressured cartridge, oh well.

Thank you for your input.
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Old 06-07-2015, 11:23 AM
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The amount of powder you dump into the case has a direct relation to the pressure in the case. The pressure in the chamber has a direct relation on the muzzle velocity. However in both instances the relationship is not linear.
.357 has twice the pressure of 38 special yet the velocity is only 50 to 70% higher.
The best way to ensure you avoid excess pressure would be to consult multiple reloading manuals and discard data that appears to be an outlier
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Old 06-07-2015, 06:32 PM
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Originally Posted by Kaedan View Post
It's funny because I have a speer manual that is brand new, and I bought one of those little booklets from cabelas that have data from numerous sources, and the data between the two is all over the place. Is one of them wrong? Is one of them being careless, or the other one being cautious? It just would be nice to know. Bummer that there are no pressure signs in such a little pressured cartridge, oh well.

Thank you for your input.
Data varies between manuals for a variety of reasons and not
because of any lack of ability to read pressures. Too many
reasons to go into here. But in general very few if any
current manuals will list data for the 38 spl that exceeds +P
levels. Back in the days of the N frame 38 spls there was
such a thing as the 38/44 38 spl cartridge available from the factories for use in heavy frame revolvers. And yes it got
used in smaller guns but that's another story. Some of the
old manuals did publish 38/44 data but you're not going to
see that happen today. However if you're really interested
in this you can order back issues of Handloader magazine
or acquire old data online I believe. There are two articles
that come to mind about loading the 38 to 38/44 levels,
one by Mike Venturnino and one by Brian Pearce. Both
actually sort of turned into experiments about seeing how
far the 38 could be pushed and went beyond factory 38/44 levels. I'm sure you would find both interesting reading. I
don't know what kind of 38 spl you own but the best
path to high performance with the .357 bore dia is just to
buy a strong 357 magnum to begin with. Lots of data around
for the magnum. There are many books available from the
publisher of Handloader magazine and one good one is
"Loading the Peacemaker" by Dave Scovill. It's a very good
read for anyone interested in loading revolvers for practical
use in the field. In it he treats the 38 spl like any other
cartridge to be used for hunting and offers loading details
and heavy handloads for field use in strong revolvers.

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Old 06-07-2015, 07:01 PM
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For target shooting I load 38spl cases with 3.0 gr of Winchester 231. standard primers and a lead wadcutter. This IMO makes just about an ideal 38 target load and I've never seen any reason to deviate from it for that purpose.
If I want something hotter I load 357 Magnums and of course only use them in revolvers chambered for this cartridge.
My wife carries a alloy J frame as a concealed carry revolver and it's loaded with commercially manufactured defensive cartridges made for this purpose.
Jim
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Old 06-15-2015, 12:18 PM
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This reminds me of something that happened to me when I first started shooting. I bought some 38 special reloads (yeah...never again), that were 158 LRN over what I believe to be tightgroup. The first shot seemed hot. My second mistake (first mistake was buying reloads), was to shoot another. Chalk it up to inexperience...that second shot felt VERY stout. I figured I'd shoot again (what was wrong with me!?!?! More inexperience)! This time the trigger wouldn't budge. Once I managed to get the cylinder open I had completely flattened primers. The first brass that was shot managed to be persuaded out with a stick. The second shot needed a punch and a hammer. It was that stuck. I returned the box to the store and of course there was "nothing wrong with the rest of them". Never bought another reload.

So from what I'm reading here is that in order to see pressure signs like I noticed, those shots were over standard 357 magnum pressures! This was shot in an airweight 38 special.
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Old 06-15-2015, 12:51 PM
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Can you elaborate on this? Seems to me increasing pressure would pretty much have to correlate to increasing velocity - and vice versa. How could it not?
The non-linearity of increased pressure with increased powder charges means that, depending on the specific powder and where you are on the loading curve for that cartridge, sometimes a very small increase in powder makes a HUGE increase in pressure. At a different point on the pressure curve, even a grain increase may still be well within limits.

Look at it this way. If you are standing on a mild slope and take a step, you are still safe. Take that step next to a cliff and you fall. You can see the curves in the earth, but you only "see" the pressure curves in a cartridge with an instrumented pressure barrel.

Most people not specifically trained have trouble visualizing non-linear rellationships, but your hearing works the same way, on a logarithmic scale of power to the loudness you perceive. Every 3 dB added sound is DOUBLE the power.
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Old 06-15-2015, 02:26 PM
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Default If you want to push pressures.....

If you want to push pressures in a .38, get a .357.
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Old 06-15-2015, 03:24 PM
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This reminds me of something that happened to me when I first started shooting. I bought some 38 special reloads (yeah...never again), that were 158 LRN over what I believe to be tightgroup. The first shot seemed hot.../

/...The first brass that was shot managed to be persuaded out with a stick. The second shot needed a punch and a hammer. It was that stuck.../

/...So from what I'm reading here is that in order to see pressure signs like I noticed, those shots were over standard 357 magnum pressures! This was shot in an airweight 38 special.
That's the criteria I use in .357 Magnum loads, although to a MUCH lesser degree. I'll work up a load until the cases just start start to "stick" and then back the load off to the point where they drop out freely.
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Old 06-15-2015, 03:30 PM
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That's the criteria I use in .357 Magnum loads, although to a MUCH lesser degree. I'll work up a load until the cases just start start to "stick" and then back the load off to the point where they drop out freely.
They were some hot 38's. . I'm just glad the gun, and my hands survived.
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Old 06-15-2015, 03:37 PM
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I doubt they are linear. If the pressure doubled, I doubt the velocity would double. Because the more the pressure gets the bullet moving, the sooner it is out of the barrel and the less time that pressure is acting on it. Double pressure for the same amount of time might double the speed (though friction isn't linear either), but when the distance and not the time is fixed, they won't have a linear correlation.
One must remember that pressure measurement is the maximum pressure in the barrel. Looking at a pressure gradiant throughout the length of a barrel, you will find the maximum pressure is within an of inch of the chamber, so unless you are shooting a snub-nosed revolver, the pressure is already dropping by the time the bullet leaves the barrel. The effect has to be linear, given the same gun is used for all tests. Increase powder, increase max pressure, and increase velocity. I did not say that it is a one to one comparison, so the angle of the graph results are not necessarily a 45 degree line, but the line should be straight.
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Old 06-15-2015, 04:58 PM
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I know you shouldn't see any pressure signs in 38 SPL, even at +P pressures, but interestingly, I had some factory ammo that flattened the heck out of the primers.

I think it was some Federal American Eagle 130 gr FMJ. Not +P either. All of the primers were about as flat as they could get. When I knocked them out, they had a mushroom shaped top. I think the material they were made out of was about as thick as tinfoil. They were not like the CCI primers I typically use.

So, with strangely thin primer cups, you might see pressure signs.

Mike
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Old 06-18-2015, 12:47 PM
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Quote:
The effect has to be linear, given the same gun is used for all tests. Increase powder, increase max pressure, and increase velocity. I did not say that it is a one to one comparison, so the angle of the graph results are not necessarily a 45 degree line, but the line should be straight.
Nothing about internal ballistics follows a linear relationship, in spite of urban myths and "common sense." The max pressure increase with increase powder charge is described accurately only by a system of second order partial differential equations (calculus) but can be approximated by an exponential curve for a particular cartridge.
A careful examination of a complete data set of charge vs pressure for a specific cartridge will show the exponential nature of the relationship.
Here's a quick and dirty reference.
Internal Ballistics

Here's a treatment that requires an understanding of differential equations.
http://www.jstor.org/stable/91246?se...n_tab_contents
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Old 06-18-2015, 02:51 PM
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Oehler Research Inc.
heres how you tell if your over, under or dead on for sure.
the rest is a guess
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Old 06-19-2015, 10:13 AM
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Nothing about internal ballistics follows a linear relationship, in spite of urban myths and "common sense." The max pressure increase with increase powder charge is described accurately only by a system of second order partial differential equations (calculus) but can be approximated by an exponential curve for a particular cartridge.
I think we are talking about two different issues. The number that SAAMI documents is a single pressure and not a time lapse pressure gradient throughout the barrel. Peak pressure rise with the addition of more powder is what I consider linear. Your graph and article refers to a pressure curve over time. As a bullet moves down the barrel, the area behind continues to increase, relieving the pressure and resulting in a lower pressure at the muzzle. I refer only to the maximum instantaneous pressure that will increase at a constant rate as powder charge increases.
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Old 06-19-2015, 12:07 PM
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I think we are talking about two different issues. The number that SAAMI documents is a single pressure and not a time lapse pressure gradient throughout the barrel. Peak pressure rise with the addition of more powder is what I consider linear. Your graph and article refers to a pressure curve over time. As a bullet moves down the barrel, the area behind continues to increase, relieving the pressure and resulting in a lower pressure at the muzzle. I refer only to the maximum instantaneous pressure that will increase at a constant rate as powder charge increases.
We are talking about the same thing: Peak pressure rise with the addition of more powder. It is approximately exponential, not linear. I debated about including the first reference, since the article includes a graph of pressure change as the bullet moves down the barrel , but that is NOT what I am talking about.

Several factors change as the powder charge inceases, such as efficiency of combustion, expansion ratio, % filled, and even the rate the powder burns. So while common sense says if I add X amount of powder the pressure increases by Y regardless of what pressure I start with, it just isn't true. Common sense does not work in internal ballistics, where the rate of change of one factor changes the amount of another factor.

Adding more powder also makes more of the powder burn (efficiency), and makes the powder burn faster, effectively increasing the peak pressure as if you had changed to a faster powder. Thus at low pressure, 6% increase of powder might give 6% increase in peak pressure, while near max recommended pressure, the same increase in powder gives 20% increase in pressure. At even higher pressures , the same increase in powder can cause 50% increase in pressure, which can cause failure.

The change of burn rate of powder with containment is the joker in the deck of powder burn rate charts, and why powders appear in different order depending on the specifics of the test, and why they cannot be applied to specific cartridges.

Internal ballistics is not only more complicated than most understand, it is perhaps even more complicated than most can understand. That's why we all use specific load charts generated by actual pressure lab equipment. I have done years of calculus classes, teach college math and physics, and understand the equations, but I still use the load charts, and am perhaps more aware than most of how dangerous it is to wander off tested data and guess that a load is safe.

We haven't even addressed such issues as pressure waves and nodes during combustion, which are factors in such rare observed anomalies as loading a bullet LONGER or reducing a powder charge and having the pressure go UP, contrary to "common sense." Normally, we expect it to go down, and usually it does. But not always.
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Old 06-19-2015, 12:20 PM
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That's the criteria I use in .357 Magnum loads, although to a MUCH lesser degree. I'll work up a load until the cases just start start to "stick" and then back the load off to the point where they drop out freely.
That does not tell you what the pressure is. You would be well advised to use published data.
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Old 06-19-2015, 12:24 PM
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Leathermech,

In a nutshell, you already had the right answer before you posted. Your thinking is correct. The cases and primers, whether .38 Spl or .357 Mag, will usually function properly beyond what some revolvers will handle. I'm not sure that the top strap is the first to go, but you have the general idea. Reminds me of a redneck torque wrench - tighten until the bolt snaps, then back off a quarter turn.

You've heard a few suggestions, and certainly you shouldn't expect better velocities than factory, but powder manufacturers' reloading manuals, or even bullet manufacturers' (minus Speer), are the way to go.

Pressure signs? Top strap is as good as any.
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Old 06-19-2015, 05:23 PM
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That does not tell you what the pressure is. You would be well advised to use published data.
Thanks for the "advice" but you both missed the point, and incorrectly assumed I was NOT using published load data.

The point you missed is that within the limits of published data, I'll stop and back the load off once I reach the point where the cases no longer snap all the way back out of contact with the cylinder wall (i.e. they start to feel slightly sticky when you eject them). The fact that the load data says I can go higher is irrelevant at that point.

For example, Hornady publishes minimum and maximum loads of of Win 296 at 16.9 gr and 20.3 gr respectively for their 125 gr XTP in the .357 Magnum. When working up a ladder in load development for both my SP101 and my Model 60, cases still fell free at 19.0 grains in both revolvers, however at 19.5 grains they started sticking slightly in both revolvers.

That load is still .8 gains under the maximum load for that specified bullet and is two columns over from the max load in the data. But none the less, it's where I curtailed the increase in powder charge due to my own personal limit, based on the failure of the case to fully retract from the chamber wall.

Now...without putting some form of pies electric monitor on the cylinder, I can't produce a specific psi figure for 19.5 gr of that particular lot of Win 296, with a 125 gr XTP, and I can't tell you whether it is over or under the 35,000 psi SAAMI limit, but I can tell you the pressure is high enough that the cases no longer snap back to the way they do at a lower pressure.

That tells me that what ever pressure is being produced is high enough to exceed the elastic expansion capabilities of the brass and is resulting in permanent expansion of the case (at least forward of the web). That's actually a lot more meaningful to me than an estimated pressure based on published load data.

After 38 years of reloading, I've learned not to trust all the published data I see, and to work loads up from the middle to find safe maximum loads - that are often less than the published data suggests.
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Old 06-19-2015, 11:44 PM
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38 years? Well, I guess that's a start!

Oh, and wut in hail is a "pies electric monitor"?
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