First off, let me say I follow the manual to the letter. I don't screw around and make guesses at loading. If the load book says it's fine, then I roll them out low and work them up to what I want within the limit. None of my loads are hot and heavy in the first place. My issue is just why the lowest common denominator type answer like a Cartridge Over All Length and not just a bullet mass in grains with amount of seating depth compared to what amount of powder gives this amount of pressure and it's all in a graph? What am I missing here?

Sir, a few reasons, mainly having to do with too many variables.

Bullets of a given weight in a given caliber can still have very different shapes, as well as different crimp groove locations, which affects seating depth and working case volume.

Jacketed bullets also have a higher coefficient of friction than lead, which means they're harder to push down the bore, and which raises pressures, all else being equal.

And if you're talking about loads that have to fit in a box magazine, that also affects permissible overall length.

There's just too many different variables to make a useful universal graph.

Hope this helps, and Semper Fi.

Ron H.

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Wishin' don't make it so.

Hmmmm, this sounds vaguely familiar

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Still Running Against the Wind

I will give this reply due to the fact that I have recently dealt with the COL issue. It is my understanding that the COL's listed in reloading manuals are the "standard" or recommended length. There are other variables to be considered. I have been messing around with an old '93 model small ring mauser. When I tried reloading to the "standard" COL the groups achieved were miserable, I did a little research and found that it is necessary to extend the COL in order to reach the lands, the bullets used back in the day were longer than the standard 7 x 57 of today. One of the things that is necessary when developing a "custom" load is make sure it is only used the rifle it is developed for. I ended up reloading with a COL that was barely short of the magazine box length, that round delivered the best group. In a modern 7 x 57 chambered rifle it would probably make closing the action negligible. Not to belabour this thread but some bullet manufactures (Barnes) also recommend achieving a COL that brings the final length just short of the lands.

First off, are we just talking handgun cartridges? Because rifle reloading is a whole nutter matter.

In the case of a handgun, too long is not that big of an issue. Usually, and especially in a revolver, you aren't going to "run into something" that will cause pressures to increase. If things get that long in say, a 38spl, most likely, you are not going to get the cylinder closed. In an auto, I suppose that you can run into similar trouble BUT, again, the action shouldn't close if too far out of battery, and still, no kaboom.

The problem is in handgun cartridges where the OAL is shortened and there is more bullet in the case than the "recipe" expected. Now, if you are doing your reloading correctly, starting low and working up will save you precious body parts and maybe even a loving bystander or two. No harm, no foul. The problem comes into play when you are using a super fast handgun powder and reduce the amount of "free space" in a case with the same amount of projectile weight. Depending on the powder, you can have a real bad episode on your hands.

Case in point: 40S&W, 180gr bullet, Clays powder, bullet setback of .060" or something more with a full charge. What are you going to have when you pull that trigger? Right, you don't know and in the wrong handgun, you could have a catastrophe.

There are other factors that play a part too, bearing surface being one of them. BUT, I firmly believe, you don't have to agree with this, that seating depth is the most critical thing to causing a dangerous pressure spike that a reloader/handloader can overlook or change.

Listen, Elmer Keith's whole premise on the designs of his bullets rests on this one point: More bullet outside the case reduces pressures inside the case. Fill that extra space with powder and then the pressure can be raised to new and exciting levels! (Just an attempt at some dry humor.)

The reality is, more empty space in a straight walled pistol cartridge, same amount of powder and bullet weight will reduce the pressure in the case. Seat the bullet deeper, pressures increase.

Just my

Different shapes is all about the top half of the bullet with a few minor exeptions like HBWC's. The bottom half of the bullet should be fairly uniform in handgun and with rifle you will get a minor difference in flat base vs. boat tail profile.

We already have lead vs. jacketed load data so I don't see how this would be much different.

If a load doesn't fit your cylinder or magazine, then it just wasn't made to fit that gun. So yes, COAL can prevent you from fitting a cartridge, but that's true of current loads with certain bullets already. Go 77 grains or larger and you have a tough time fitting in most AR's. That doesn't mean you just stick with the same COAL and seat them deeper...

I know, I'm still stuck in the mud on this issue. I keep feeling like I'm right at the edge of understanding it and then I fell on my face. I'm hoping that if I keep bringing it up then either I will peice something together or someone will have a burst of brilliance.

I think there will always be room for making a call on your load for it being gun specific. I already make a couple of loads for a certain gun that favors them. My issue is the current standard guidelines leave a LOT of gray area when you are loading. Most, not all, but most cases have a fairly uniform volume. I'm not including milsurp cases since they were made load specific to the weapon in the first place. The more of that volume you use, the less volume remains for the gas to expand in and thus more pressure with the same amount of powder. Seating depth would still leave some variables in the shady area, but it still seems like it would be better than just seat them all to this over all length...

I'm only talking same same for both handgun and rifle in that the same volume + the same powder + a decrease/increase in case volume from bullet seating depth = a increase/decrease in pressure generated by powder during ignition. I highlight in bold what you said since I feel like I'm saying the same thing. And yes, more bullet outside the case means more volume inside the case and thus less pressure made by the same amount of powder. So once again... Seating depth would seem to be a better way of looking at this issue than COAL...

So I'm still stuck in the mud. Bullet profile with COAL still seems like it have a vast amount more variable to it than bullet seating depth ever would.

Thats the trouble with using COAL, is doesn't take into account bullet shapes but is a compromise.

I’ll address rifle cartridge OAL. If you’re only reading the recipes in the manuals, you’re missing “the rest of the story”. If you have a Nosler reloading manual, go to the front of the book and look for the section titled “Proper bullet seating” (it’s on page 42 of their 5th edition). The instruction paper included with my RCBS dies covers the same material. Basically, what they say is to measure the distance from the ogive to the start of the rifling and seat your bullets .015” to .030” off the rifling for best accuracy. Companies like Sinclair Int. sell specialized tools to measure the distance, but the method outlined by Nosler and RCBS is much less expensive and it works too. They tell you to slightly deform a non-resized case mouth to form a “D”, partially insert you bullet of choice and paint the sides of the bullet with a permanent marker or Sharpie. When you close the action, the rifling seats the bullet and the deformed case mouth scrapes the ink off and shows you where it stops. Because different bullets have different shape ogives and different rifles have varying amounts of free-bore, the sweet spot varies. As mentioned in previous posts, the SAAMI OAL is designed to insure that factory produced rifles and factory produced ammunition are compatible, they’re not designed to yield maximum accuracy.

Altering the OAL is an advanced reloading technique that can provide amazing results. A friend of mine worked up some loads for his .300 Win Mag before a recent elk hunt. His rifle, a Remington 700BDL, was only grouping about 2” at 100 yards with his best load (IMR7828, 180gr Nosler Partition). We measured the distance to the rifling and found that the bullet had to jump over .125” before it reached the rifling. I suggested he load a few batches of cartridges, seating the bullets .015”, .020”, .025” and .030” off the rifling. I went back to the range with him after he worked up the loads and .025” was the sweet spot; groups were right around 1”. All of the longer loads shot substantially better than SAMMI COAL, but the .025” load was noticeably better and he ended up taking the heart out of an elk at just over 300yds. The load fit in his magazine with room to spare and there were no signs of excess pressure. My 700 in .22-250 is similar and I load 50gr Nosler BT’s almost .125” over SAMMI; it cuts my groups in half. On another rifle of mine (a custom Remington 40X chambered in 6mm PPC-USA with a .262” neck), I actually seat Rubright 65gr bullets into the rifling. This is definitely NOT recommended on anything but a benchrest gun. The gun shoots about .2” on a calm day, but once a cartridge is chambered it has to be shot. If you try to open the action on a loaded cartridge, the rifling pulls the bullet, it dumps powder into the lug cuts and the gun’s out of commission until it’s cleaned. With a 2oz Timney trigger and no safety, it's a very specialized too!

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"I also cook."

S&Wchad -

I feel bad for the gnat's wings when you clip them.

I am right there with you on optimizing the bullet in a rifle load, but I'm only talking basics. Since there is so much room for change in many rifle loads, maybe this applies more to pistol loads. But the heart of what I'm trying to say should still hold true.

And if that was my rifle, I would call her "Plum Crazy"...

The Mopar generation may have been before my time, but I'm still in awe of what kind of cars we used to make.

The only example I can give you is the use of a 115 or 124 gr LRN in either a CZ or Browning HP.

Both of these guns have funky barrels or "leades", chambers, whatever. There is no way to use the printed load data of OAL to seat the bullets to fit these guns (using MBC bullets) the bullet is so rounded it jams in the barrel using the "preferred" OAL.

I need to seat them much deeper in order for them to chamber. Doing so I need to reduce or at least use the min powder charge.

If I use a FMJ bullet with more of a pointed profile, all is well.

So to me, it all depends on the guns particular barrel.

OAL does not work well with bullets that have a cannelure as you normally would seat to the goove but most manuals have a "trim to length" which is a fraction shorter and most handgun brass is not trimmed to that length.

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Still Running Against the Wind

The only lead my BHP has seen is the truncated cone tumble lube bullets from my Lee mold. They worked fine, but they aren't round nose. Sounds like what Skip was saying about more of the bullet being outside the case. Which brings me back to my point... I hope my TC's aren't seated too far...

Measure the bullets in question, measure the bullets in the data, compare SEATING depth at OAL listed. If SEATING depth is deeper, as Rule has so wonderfully explained, reduce or use minimum loads.

It really is pretty simple to get a grasp on. I think you have it, it is just ODD to our "feed me the info and I will perform" mentality of today. When men used to do math in their heads and thought a calculator was silly. Back when folks that loaded understood what was more important, OAL or seating depth. Folks like Keith and Sharpe and ................ now, hopefully you and I.

That's why you use the "plunk and drop test" with the barrel out of the gun. Seat them long and keep testing untill in drops in and out (with a crimp) and go with the "magic" length that works and adjust your powder if needed.

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Still Running Against the Wind

I think I can at least see the light at the end of the tunnel.

If I load for an auto, I pull the barrel and make sure it drops in flush with the barrel hood. I find that so far all my seating depth use has worked so far. But I didn't think about how much bullet is going into the case on those TC bullets. I loaded those a while back before I got all concerned about this issue. They worked fine, but it does make me think that I didn't have to work them up at all for function. I started low and they just worked...

NOW even I understand. Just got reloading equipment for Christmas, trying to pay attention to what I need to do first. First, don't blow nuthin' up! When I finally get the last bits and pieces together, (including the actual powder, bullets, primers, etc), hopefully all this will REALLY make sense.

I was led to believe that dry humor was not appreciated in this forum.

No, humor that is labeled as humor, some forums want you to put it in purple so everyone knows you are kidding, is always appreciated.

When you get around a bunch of gun nuts, paranoid already because we have a democrat in office, threaten legal action as has taken place on other forums, (at least rumored to have taken place), people tend to react accordingly.

You will be laughed with or at, as the case may dictate, when you label your humor as such.................... (Case in point!)

I hate that we are taking time away from the OP's question, but, I usually don't let things slide too well!

I think you are getting a little deep in the cartridge on this one...

(insert knee slapping smiley here)

No, you just need to fully explain it for those who can not grasp it. (and use a lot of these things)

Just imagine if Sipowicz reloaded???

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Still Running Against the Wind

I take it you didn't hear about the "earthquake" in NZ??

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"I also cook."

I did, but did not realize he was responsible for it.

His little light is on (not that it means anyone is home)

How's that for dry?

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Still Running Against the Wind

Rule3, you are the Great Sahara...

I'd like to "like" just about all the posts! But instead just a quick thanks to the contributors, this has been a great read.

So the jist of this (from what I gather as a new reloader) is:

-The COAL in the manuals are minimums to keep pressures safe.
-Accuracy MAY be increased by seating a long (keeping gun function in mind), without increasing pressures to unsafe levels.
-If one goes off the books, use a min COAL and start seating deeper if desired with lower charges and work back up, because pressures will rise.

Seating over COAL can increase pressures if the bullet is too close to the rifling, that's why Nosler recommends .015 to .030" off. Weatherby provides a lot of free-bore because their cartridges are hot and I wouldn't get closer than about .030" off. On benchrest guns, the heavy custom barrels, trued locking lugs and the lower cartridge pressures allow a lot of leeway. Always work up to maximum loads when you change something and look for signs of excess pressure (difficulty opening the bolt, flattened primers, etc...).

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"I also cook."

Well, sorta, kinda maybe.

First, rifle and handguns are different animals. True benchrest rifle shooters try to get the bullet just off the lands. For handguns it's not that important and with revolvers it's a whole different story.

The main issue is the posted OAL in manuals is using that specific bullet. Say you look at a Speer Manual, that info is for their bullet. So if you use a different brand it could be a bit different as the mold is different. If the weight and overall shape of the bullet is pretty close, you are safe to use the given data. There are just so many different brands out there it's impossible to have an exact length for every one of them.

Thats why it is good to check several manuals, if you are within a fraction of all of them then test a few in your barrel (an inert round, seated and crimped and see if it drops in the barrel with a "plunk" and seats correctly, turn it over and it should fall out. You can experiment with a few long ones, with no crimp and see how the stick or do not seat, gradually seat them a bit and when you hit the right length they will chamber.

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Still Running Against the Wind

love my barrel guage thingy.. (name escapes me sorry) if it sticks out, too long.. looks to short I make it longer. OAL confused the **** out of me when I first started reloading. It still confuses me but Ive learned to accept that and work inside what I have came to know as safe parameters. What I also have learned is the basics, rifles want the OAL for a good "jump." semi-auto handguns want it to cycle smoothly, revolvers need it to fit.. basics. all been said before. You can play around with the COAL and see what works best for you. Just remember to stay within the printed "safe" parameters, or wear iron gauntlets and face helm, every time you go shooting as a precaution.
good luck.

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sw9ve, 24/7 pro Ds, Hs M4

Using a 115 gr. Hornady XTP in two 9mm pistols: load is WIN 231 4.9 gr. (which is 0.20 gr. under the MAX) per the LEE load data that came with their die set.

When loaded at an O.A.L. of 1.125" (their suggested figure) the bullets will not pass the "plink test" in a 3rd Gen chamber. No problem with the CZ-75, which supposedly has a more restrictive chamber, but has in my experience no problem chambering or functioning with ANY factory ammo I have ever encountered. Most factory hollow point 9mm loads are much, much shorter, according to my measurements, BTW.

Loaded 0.005 deeper (i.e., @ 1.120") there is no problem at all with the 3rd Gen.

What is the practical estimated difference in seating the bullet 0.005" deeper vis-a-vis pressure? At 0.20 gr. of WIN 231 under the published MAX, is it really too small to have any real negative effect on this being a "SAFE" load?

Not sure what the question is but I seriously doubt you follow the load data to the letter. That means exact bullet, case primer, charge wt & OAL. I don't know anyone that can honestly claim that. Then again, if you never leave midrange loads, none of that really matters.
The one true statement about OAL, regardless of the data, the load MUST FIT YOUR gun. So data points become suggestions not gospel. If you have to shorten OAL & you are already at max load levels, then you will have to adjust powder charges in handgun loads. Again, never leave midrange, OAL doesn't impact pressures as much, regardless of the caliber loading for.

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NRA Cert. Inst. IDPA CSO

Yep now I know why they use purple for humor, I can't even read it against the black back ground. Don

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USN Retired/VN VET
M&P X5

Are you replying to the OP from 2011? or the post from Storming Norman?

I think Bob has figured out his question over the last 4 years.

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Still Running Against the Wind

Quote from OP: " My issue is just why the lowest common denominator type answer like a Cartridge Over All Length and not just a bullet mass in grains with amount of seating depth compared to what amount of powder gives this amount of pressure and it's all in a graph? "

The simple answer, which as you say seems to be just out of your reach, is this: Bullet mass in grams does not describe length, shape, or material composition . . . and seating depth is impractical to directly measure other than by COL.

Take two identical bullets and two cases identical other than 0.001" in case length. Seat the bullets to the same seating depth, measured from the only practical measuring point ie the case neck. The two completed cartridges will have different internal volumes.

OTOH, seat the bullets to identical COLs and the cartridges will have the same COL and interior volume. The variation, in this case 0.001", occurs only in how much bullet shank is grabbed by the case neck.

So, assuming identical bullets and cases identical other than length, this approach actually assures identical interior case volume.

COL is easy to measure, and the resulting case will also fit in spaces like magazines that do not care about interior case volume, but very much care about COL.

Note that in high pressure loads, the more important volume for avoiding maximum pressure is the chamber volume. Quickload, eg, specifies measuring those case volumes from fired, not resized, cases.

Keep your powder, and your humor, dry.

I have Dillon case gauges for 9mm, 38 Super, and .45 ACP. A lot easier than disassembling my pistols so I have the barrel on my loading bench.
Works great for most everything, EXCEPT my Sig C3. Chamber must be undersized, as cartridges fitting the .45 case gauge won't necessarily fit the C3. Bit of a p****r finding out at the range. My other 1911 .45 will eat anything that fits the case gauge.

The problem with case Gage's, they don't have rifling, so are useless for checking proper oal. At some point you have to make sure the bullet fits. Then you can use the gage to check proper sizing & crimp, all they are good for.

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NRA Cert. Inst. IDPA CSO

Good point. My bullets are surely running into the rifling, and the case gauge is only a chamber gauge.

I hate to say it (this is not directed at any single person) but there's sooooo much mis-information out there, what people think they understand and the lack of knowledge on what to look for.

I see anything from undersized chamber to no need to crimp to the plunk test to slug the bbl to thin walled brass.

I'm not picking on titegroup, it's an excellent powder. It just seems that every time I read about a kaboom anymore it's titegroup 9mm or titegroup 40s&w combo. Titegroup is an excellent powder but it's also very unforgiving.

There are excellent reloaders (actually some of the best out there) on this forum. Perhaps a new thread on the subject of reloading for the semi-auto's would be useful to new and old reloaders alike. Talk about bbl's and what to look for along with what equipment works for what bullet/bullet diameters would be useful.

COL - COL - COL Not COAL Overall is one word.

I recognize this thread was from a way back but thought I was asking a legitimate question: does a reduction of the C.O.A.L. (or O.A.L., if you prefer?) of 0.005" in a midrange loading as described above to allow a successful "plink test" really amount to anything as far as SAFETY is concerned?

Thanks!

p.s. I was certainly pleased with the number of responses but a little surprised that not one really answered my query.

NO, not that you can detect or that exists. But with a laboratory full of ballistic testing equipment, that is certified and calibrated, you MIGHT measure a detectable difference.

Your hand will never notice the difference.

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S&WHF 366

No it does not matter .005" is nothing.

You have a bit of room to adjust your COL for the PLUNK test.

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Still Running Against the Wind

Thank you both for answering my query.

I guess my only question remaining would be why a published load (whether from a bullet, die or powder manufacturer) that includes a C.O.L. (thanks for the info, BTW!) and supposedly conforms to all the SAMMI specifications regarding diameter, case dimentions, primer hole size, etc. doesn't take the specific bullet's profile(?) into consideration?

Looking at the chamber for a 9mm Parabelum pistol: it is sized to accept the SAMMI spec ammo, is it not? There is what is probably the outline of a FMJ shown in the SAMMI diagram.

Why would the published load info not take bullet profile (if that is the correct term) into consideration vis-a-vis the suggested C.O.L.?

SAAMI specs are the MAXIMUM COL, kind of a standard,

The manuals do take into account the profile of the bullet, that is why there are different COL.

Every manual or online data uses different bullets and the seating depth can vary a lot. Flat nose, HP, RN etc.

Take a 115 and 124 gr bullet in the 9mm. Were is the extra weight? Usually in the driving band so there is more of the bullet in the case if you keep the same COL, also why heavier bullets usually use less powder.

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Still Running Against the Wind

Loading data is for a specific bullet. But Sierra's 115 gr bullet may have a different shape than Speer's. You might find data for one but not the other. So you crib it, realizing you may have to adjust the COAL.

No, not even with max loads. Go look at 0.005", not even a sheet of paper. Bullet noses vary more than that in the same lot.

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NRA Cert. Inst. IDPA CSO

Just a little good natured ribbing.

I posted a thread a while back wondering if .003" variance was enough to worry about in my hand loads. On a suggestion, I measured a random handful of rounds of WWB 115gr 9MM.
The variance of factory ammo was all over the place. I think I measured a span of .007" +/- if I remember correctly.

With that in mind and with some of the advice from long-time hand loaders here, it sounds like you're ok.

For my 45 autos I use the plunk test. Drop a unloaded but bullet seated long into the chamber. Then adjust col so that cartridge base is where I want it then make up a bunch of dummies and hand cycle to check on feeding and extraction. If ok then load cases with the Dillon dies set for that case and bullet combination. I couldn't tell you how many 45 acp cartridges I've loaded this way. no failures to feed or extract. Revolver cases get trimmed to the same length. This makes it way easier to get good crimps on the cannulures on the bullets. None of my pistol or revolver loads are at no where near maximum. Rifle cartridges same thing I prep the brass by uniforming the flash holes,primer pockets and trim all to the same length. Seating depth in my bolt action rifles will be done so as to get close to the origin of the rifling. Usually may take a few trips to the range to check accuracy. Again checking for feeding and extraction as well as accuracy. Cast bullets in my Finnish reworked model 27 moisin nagant rifle circa 1935 is done completely different. Trim cases, uniform primer pockets and flash holes. Slightly expany case necks with a lyman "M" die. Seat bullet and no crimp. Many years ago I got some 7/8"x14 tpi threaded rod which is the same size as most reloading dies. Drilled then reamed a short section (1.5") to make a shorty neck sizer for the one bullet I shoot in this rifle. This sizes the neck to hold that bullet without overworking the brass in fact only about .003-.004 max. I get 2" groups at 100 yds when my eyes can see the issue sights. Bullet is only going about 1600FPS so my main goal is accuracy. Frank

What makes you think the published load does not take the bullet's profile into consideration? Of course it does.

If you make a cartridge with the specific components and COL listed, and if the case is sized and dimensioned within SAAMI spec . . . it WILL chamber in any factory firearm that meets SAAMI specs for that caliber. However:

It may not feed in a specific semi-auto at that COL. The interior geometry of the mag, bolt, and/or feed ramp, and their relationship to the chamber and bullet profile may benefit from a different COL.

It may not fit in a magazine because the bullet's weight and profile force it to be seated at a COL longer than magazine length. But it will chamber in a SAAMI-spec firearm of that caliber.

It may or may not fit in a custom chamber.

I just depends.............

Do you want the test load to go..... "Plink" or

"Plunk" ?

Something to think about:
Most reloaders don't have the equipment or the skill set to make consistent ammo.
Most power measures don't throw consistent charges.
Unless you're using trimmed brass from the same lot there are differences in case volume and neck tension.

This is why I say there's sssoooooooo much information out there. At the end of the day your:
Going to make ammo with a +/- .005" difference in oal. so your ammo is going to be as much a .010" shorter than your documented oal.
You powder is .02gr under max, most throws with powders it likes are +/- .01gr and will throw .02gr every now and then.
Brass is extremely different between mfg's and the different font's for the same brass signifies changes in design. Brass made 10yrs ago doesn't have the same beefed up web that most brass uses today. Thicker webs ='s less case volume.

Well lets get down to it:
The 9mm's are more likely to have issues with oal's than other calibers. It's a high pressure extremely low volume cartridge/case. Ramshot put an interesting graph out showing this very thing with their fast burning zip powder.



While not a huge difference in pressure change, it's still there. Couple that with other normal reloading extremes, the reloader ends up with huge pressure spikes/swings. That's why a chronograph is an extremely useful tool in the reloader bag.

Look at it this way, at the end of the day if you load 1000 rounds of the load in question you'll end up with the majority of them in the zone/cone of reloading you were targeting. The remaining lesser reloads will be in the extremes/outer parameters of what you wanted to reload.

A load with -.02gr and a +.005" oal is no harm no foul. The other end of the extremes in reloading is what gives reloaders problems. A +.02gr and a -.005" oal is a huge swing in pressures. From your original load standpoint the lower extreme load has a .02gr lighter charge. The higher extreme is .02gr higher and .010" oal smaller.

Every reloader is different, myself I take my time and weigh charges of a powder I've never used for awhile (1/2hr/couple of hundred throws) to get a good idea of how the powder/powder throw combo interact. During the testing I'll use different baffles and different combos of baffles to see what is the most consistent for that powder in that throw.

I'll also measure the oals of a bullet when I 1st load them (100 rounds) to get an idea of how consistent a set of dies/seating stem combo is with that bullet. I have changed seating stem to get a more consistent oal.

Doing those things will let the reloader know what their extremes are with that load. It's the extremes in reloading that create the problems. If the reloader sees anything that looks bad they can change their load to make the extremes safer.

The plunk test is 1 of the most mis-used/mis-understood pieces of info out there!!!!! I know, I know, how hard can it be???? REALLY????

Ya, REALLY!!!!

When people use the plunk test to check the oal of the bullet, they are actually checking the throat of the bbl, not the chamber.

Step 1:
Take an empty case and size it, expand/flare it for a bullet, then cycle it thru the seating die and crimp die with no bullet. Now do a plunk test.

There, you used the plunk test to check your load/bbl's chamber combo.

Step 2:
Do the same as above but this time use a bullet and make up a dummy round. Now do a plunk test again, this time the plunk test is checking the bullets oal/where it meets the throat of the bbl. Has nothing to do with the chamber, it's all about the bullet/throat fit.

Everyone see's the "Best accuracy" and loads for that, great!!!! Guess what happens when the wrong bullet shape/rock hard bullet combo is paired up with this max oal. Any build-up/fouling in the bbl's throat will cause bullet setback. Any time a bullet is loaded with a longer oal than plunk tested, the bullet will setback.

The best accuracy is for "LEAD" bullets. The "NORMAL" load is for jacketed.



The 1st thing a reloader should look at when they reload for a semi-auto is the bbl, more specifically the throat of the bbl. Mfg's are getting cheaper and are leaving out a step in bbl making, the throating reamer.

A bbl that has not had a throating reamer used in it. Note the short throat/space between the end of the chamber and abrupt angles on the lands.



The same bbl that has been throated, note the longer space between the end of the chamber and the angles of the lands.



When you're doing a plunk test with a bullet, this is what your hitting/measuring. That's called using the plunk test to get a bullet/bbl throat oal. The bbl's chamber has absolutely nothing to do with a bullets oal. I could run that throating reamer another 1/2" in that bbl and a reloader wouldn't be able to do a plunk test, bullets wouldn't be long enough. Same bbl, same chamber, just different throat lengths.

Anyway, a little insight on what your actually measuring, what your slamming your bullets into when you set the oal to max and the affects of pressures at different oals, coupled with the idea you might consider looking at/measuring/testing your skill set/reloading equipment to know just how accurate you are with your reloading.

Perhaps a reloader could look at both bbl's chambers and different bullet designs and find a bullet that will have the same oal for both bbl's. Hence: different nose shape/1r, octive +fp,rn,swc,fp, fp 20* shoulders, etc.

In testing home swaged jacketed bullets, I found that the oal isn't as touchy with a fn design with sholder angles in the 20+* range when compared to swc's and rn designs. A 147gr fnhp with 23* shoulders.