Smith & Wesson Forum

Advertise With Us Search
Go Back   Smith & Wesson Forum > Ammunition-Gunsmithing > Reloading

Reloading All Reloading Topics Go Here


Reply
 
Thread Tools Display Modes
  #1  
Old 06-01-2015, 08:47 PM
leathermech leathermech is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Jun 2013
Location: Texas
Posts: 7
Likes: 1
Liked 2 Times in 2 Posts
Default 38 Special pressure signs

I’m asking the question now because I’ve never thought to ask it. “What pressure signs?”

While browsing a forum discussing working up loads for the 38 Special, talk turned to Keith’s 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 that’s 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).

Here’s what I’m 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. 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.

Before you hit your reply button, please accept that I’m 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 wasn’t 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 P’s to land in magnum range without observing the pressure signs depicted in a loading manual. The specials are easily wolves in sheep’s cylinders and I think the pal missed the lesson.

What pressure signs?? Thoughts?
Reply With Quote
  #2  
Old 06-01-2015, 09:50 PM
TucsonMTB's Avatar
TucsonMTB TucsonMTB is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Sep 2011
Location: Tucson Arizona
Posts: 1,129
Likes: 1,948
Liked 1,035 Times in 484 Posts
Default

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.
Reply With Quote
  #3  
Old 06-01-2015, 09:57 PM
Alk8944's Avatar
Alk8944 Alk8944 is online now
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Jan 2007
Location: Sandy Utah
Posts: 8,789
Likes: 1,614
Liked 9,007 Times in 3,585 Posts
Default

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!
__________________
Gunsmithing since 1961

Last edited by Alk8944; 06-01-2015 at 10:02 PM.
Reply With Quote
  #4  
Old 06-01-2015, 10:08 PM
rwsmith's Avatar
rwsmith rwsmith is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Dec 2012
Location: (outside) Charleston, SC
Posts: 31,038
Likes: 41,730
Liked 29,302 Times in 13,853 Posts
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.
__________________
"He was kinda funny lookin'"
Reply With Quote
The Following 4 Users Like Post:
  #5  
Old 06-01-2015, 10:33 PM
alwslate alwslate is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Dec 2009
Location: Indiana
Posts: 6,653
Likes: 3,748
Liked 7,275 Times in 3,025 Posts
Default

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.
Reply With Quote
The Following 3 Users Like Post:
  #6  
Old 06-01-2015, 10:49 PM
BB57's Avatar
BB57 BB57 is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Feb 2015
Location: NC
Posts: 4,766
Likes: 3,569
Liked 12,740 Times in 3,386 Posts
Default

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.
Reply With Quote
The Following User Likes This Post:
  #7  
Old 06-01-2015, 10:57 PM
Bruce51's Avatar
Bruce51 Bruce51 is offline
Member
38 Special pressure signs  
Join Date: Sep 2006
Location: Left coast
Posts: 1,439
Likes: 441
Liked 626 Times in 301 Posts
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
Reply With Quote
The Following 3 Users Like Post:
  #8  
Old 06-03-2015, 10:04 PM
jtcarm's Avatar
jtcarm jtcarm is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Apr 2011
Posts: 4,380
Likes: 1,556
Liked 4,276 Times in 1,808 Posts
Default

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.
Reply With Quote
  #9  
Old 06-03-2015, 11:39 PM
BC38's Avatar
BC38 BC38 is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Nov 2013
Location: Spokane, WA
Posts: 13,552
Likes: 1,189
Liked 18,510 Times in 7,331 Posts
Default

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?
Reply With Quote
  #10  
Old 06-01-2015, 10:39 PM
ChiefStealth's Avatar
ChiefStealth ChiefStealth is offline
US Veteran
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: May 2014
Location: Graham, Wa.
Posts: 447
Likes: 8
Liked 246 Times in 134 Posts
Default

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.
Reply With Quote
  #11  
Old 06-01-2015, 11:16 PM
DWalt's Avatar
DWalt DWalt is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Dec 2009
Location: South Texas & San Antonio
Posts: 33,768
Likes: 248
Liked 29,334 Times in 14,175 Posts
Default

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.
Reply With Quote
The Following User Likes This Post:
  #12  
Old 06-02-2015, 01:08 AM
Nevada Ed's Avatar
Nevada Ed Nevada Ed is offline
US Veteran
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Nov 2012
Location: Reno Nv
Posts: 13,418
Likes: 3,196
Liked 12,785 Times in 5,697 Posts
Default

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.
Reply With Quote
  #13  
Old 06-02-2015, 10:22 PM
BB57's Avatar
BB57 BB57 is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Feb 2015
Location: NC
Posts: 4,766
Likes: 3,569
Liked 12,740 Times in 3,386 Posts
Default

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.
Reply With Quote
The Following User Likes This Post:
  #14  
Old 06-02-2015, 02:07 AM
BLUEDOT37's Avatar
BLUEDOT37 BLUEDOT37 is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Dec 2012
Location: N.E. OKLA.
Posts: 6,496
Likes: 5,898
Liked 9,368 Times in 3,507 Posts
Default

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.

.
__________________
Waiting for the break of day

Last edited by BLUEDOT37; 06-02-2015 at 02:07 AM. Reason: .
Reply With Quote
  #15  
Old 06-02-2015, 08:09 PM
scooter123 scooter123 is offline
Member
 
Join Date: Jan 2009
Location: Metro Detroit, Michigan
Posts: 6,931
Likes: 179
Liked 4,313 Times in 2,114 Posts
Default

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.
Reply With Quote
  #16  
Old 06-03-2015, 05:55 AM
MJFlores MJFlores is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Apr 2014
Location: New Hampshire
Posts: 408
Likes: 156
Liked 570 Times in 158 Posts
Default

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.
Reply With Quote
  #17  
Old 06-04-2015, 09:19 AM
glowe's Avatar
glowe glowe is offline
US Veteran

38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Nov 2009
Location: Michigan Western UP
Posts: 12,997
Likes: 3,060
Liked 14,435 Times in 5,492 Posts
Default

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.
__________________
Gary
SWCA 2515

Last edited by glowe; 06-04-2015 at 09:24 AM.
Reply With Quote
  #18  
Old 06-04-2015, 08:09 PM
aurora40 aurora40 is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Sep 2013
Posts: 247
Likes: 34
Liked 82 Times in 62 Posts
Default

Quote:
Originally Posted by glowe View Post
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.
Reply With Quote
  #19  
Old 06-15-2015, 03:37 PM
glowe's Avatar
glowe glowe is offline
US Veteran

38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Nov 2009
Location: Michigan Western UP
Posts: 12,997
Likes: 3,060
Liked 14,435 Times in 5,492 Posts
Default

Quote:
Originally Posted by aurora40 View Post
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.
__________________
Gary
SWCA 2515
Reply With Quote
  #20  
Old 06-04-2015, 08:21 PM
ModernRifle's Avatar
ModernRifle ModernRifle is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Feb 2015
Location: Western Washington
Posts: 223
Likes: 851
Liked 689 Times in 174 Posts
Default

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.

Last edited by ModernRifle; 06-04-2015 at 11:10 PM.
Reply With Quote
The Following User Likes This Post:
  #21  
Old 06-04-2015, 08:29 PM
gwpercle's Avatar
gwpercle gwpercle is online now
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Nov 2011
Location: Baton Rouge, La.
Posts: 6,892
Likes: 7,526
Liked 8,175 Times in 3,692 Posts
Default

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!
Gary
Reply With Quote
  #22  
Old 06-05-2015, 07:38 AM
Magload Magload is offline
US Veteran
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Feb 2015
Location: NE Florida
Posts: 2,003
Likes: 217
Liked 693 Times in 462 Posts
Default

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
__________________
USN Retired/VN VET
M&P X5
Reply With Quote
  #23  
Old 06-05-2015, 10:21 AM
Bob T's Avatar
Bob T Bob T is offline
US Veteran
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Apr 2013
Location: North Alabama
Posts: 224
Likes: 517
Liked 227 Times in 89 Posts
Default

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.
Reply With Quote
  #24  
Old 06-07-2015, 11:23 AM
reddog81 reddog81 is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Sep 2014
Location: IA
Posts: 1,738
Likes: 1,005
Liked 1,635 Times in 806 Posts
Default

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
Reply With Quote
The Following User Likes This Post:
  #25  
Old 06-07-2015, 07:01 PM
italiansport italiansport is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Oct 2007
Location: Arizona
Posts: 3,222
Likes: 2,905
Liked 5,333 Times in 1,869 Posts
Default

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
Reply With Quote
  #26  
Old 06-15-2015, 12:18 PM
Boogsawaste's Avatar
Boogsawaste Boogsawaste is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Jun 2013
Location: Quakertown PA
Posts: 1,475
Likes: 4,773
Liked 1,181 Times in 491 Posts
Default

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.
__________________
Jim
Reply With Quote
  #27  
Old 06-15-2015, 03:24 PM
BB57's Avatar
BB57 BB57 is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Feb 2015
Location: NC
Posts: 4,766
Likes: 3,569
Liked 12,740 Times in 3,386 Posts
Default

Quote:
Originally Posted by Boogsawaste View Post
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.
Reply With Quote
  #28  
Old 06-15-2015, 03:30 PM
Boogsawaste's Avatar
Boogsawaste Boogsawaste is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Jun 2013
Location: Quakertown PA
Posts: 1,475
Likes: 4,773
Liked 1,181 Times in 491 Posts
Default

Quote:
Originally Posted by BB57 View Post
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.
__________________
Jim
Reply With Quote
  #29  
Old 06-19-2015, 12:20 PM
Warren Sear's Avatar
Warren Sear Warren Sear is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Apr 2011
Location: Twin Cites, Minnesota
Posts: 5,166
Likes: 11,025
Liked 10,914 Times in 3,289 Posts
Default

Quote:
Originally Posted by BB57 View Post
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.
Reply With Quote
The Following User Likes This Post:
  #30  
Old 06-19-2015, 05:23 PM
BB57's Avatar
BB57 BB57 is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Feb 2015
Location: NC
Posts: 4,766
Likes: 3,569
Liked 12,740 Times in 3,386 Posts
Default

Quote:
Originally Posted by Warren Sear View Post
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.
Reply With Quote
  #31  
Old 06-19-2015, 11:44 PM
Warren Sear's Avatar
Warren Sear Warren Sear is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Apr 2011
Location: Twin Cites, Minnesota
Posts: 5,166
Likes: 11,025
Liked 10,914 Times in 3,289 Posts
Default

38 years? Well, I guess that's a start!

Oh, and wut in hail is a "pies electric monitor"?
Reply With Quote
  #32  
Old 06-15-2015, 04:58 PM
Vortec MAX Vortec MAX is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Oct 2014
Posts: 447
Likes: 94
Liked 254 Times in 140 Posts
Default

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
__________________
NRA Certified Pistol Inst.
Reply With Quote
  #33  
Old 06-18-2015, 12:47 PM
OKFC05 OKFC05 is online now
Member
38 Special pressure signs 38 Special pressure signs  
Join Date: Aug 2007
Location: Oklahoma
Posts: 8,164
Likes: 3,635
Liked 5,215 Times in 2,176 Posts
Default

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
__________________
Science plus Art

Last edited by OKFC05; 06-18-2015 at 02:35 PM.
Reply With Quote
  #34  
Old 06-19-2015, 10:13 AM
glowe's Avatar
glowe glowe is offline
US Veteran

38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Nov 2009
Location: Michigan Western UP
Posts: 12,997
Likes: 3,060
Liked 14,435 Times in 5,492 Posts
Default

Quote:
Originally Posted by OKFC05 View Post
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.
__________________
Gary
SWCA 2515
Reply With Quote
  #35  
Old 06-19-2015, 12:07 PM
OKFC05 OKFC05 is online now
Member
38 Special pressure signs 38 Special pressure signs  
Join Date: Aug 2007
Location: Oklahoma
Posts: 8,164
Likes: 3,635
Liked 5,215 Times in 2,176 Posts
Default

Quote:
Originally Posted by glowe View Post
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.
__________________
Science plus Art

Last edited by OKFC05; 06-19-2015 at 12:17 PM.
Reply With Quote
The Following User Likes This Post:
  #36  
Old 06-18-2015, 02:51 PM
venomballistics's Avatar
venomballistics venomballistics is offline
Member
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Aug 2007
Location: between beers
Posts: 8,922
Likes: 4,789
Liked 6,986 Times in 3,330 Posts
Default

Oehler Research Inc.
heres how you tell if your over, under or dead on for sure.
the rest is a guess
__________________
it just needs more voltage
Reply With Quote
  #37  
Old 06-19-2015, 12:24 PM
ImprovedModel56Fan ImprovedModel56Fan is offline
US Veteran
38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs 38 Special pressure signs  
Join Date: Dec 2002
Location: MA
Posts: 7,355
Likes: 7,566
Liked 5,596 Times in 2,567 Posts
Default

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.
Reply With Quote
The Following 2 Users Like Post:
Reply


Posting Rules
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
320gr. .44 Special standard pressure? Andy Griffith Reloading 16 07-22-2018 08:33 PM
Buffalo Bore standard pressure .38 Special? shouldazagged S&W Revolvers: 1980 to the Present 9 03-24-2013 06:57 PM
safe pressure of .44 Special handloads Daimler1989 Reloading 21 10-14-2012 05:35 PM
Why is my brass showing high pressure signs? sbeatty1983 Reloading 24 09-19-2012 09:52 AM
Chamber pressure and primer signs Engineer1911 Reloading 16 11-02-2009 03:44 PM

Powered by vBadvanced CMPS v3.2.3
smith-wessonforum.com tested by Norton Internet Security smith-wessonforum.com tested by McAfee Internet Security

All times are GMT -4. The time now is 03:33 PM.


Smith-WessonForum.com is not affiliated with Smith & Wesson Holding Corporation (NASDAQ Global Select: SWHC)