Pressure signs when reloading for auto pistols

[micksis86]

I've been reloading for rifles for a while now and i'm about to start loading some 9mm. My question is what are the pressure signs to keep an eye out for when using your loads in auto pistols? I'm aware of the signs for rifle but i thought that since they operate quite differently (i've only loaded for bolt and lever action rifles) then the signs of high pressure may be different aswell.

[QBall45]

Pressure signs are much thr same.

Flattened primers, split case walls, case head seperation.

You really need to watch for double charges. While most all rifle charges would spill over if dounled. The same can not be said of handgun charges. I load using a load block & a single stage press. This allows inspection of the lot a the same time. No more squibs & if I double charge one its easy to pick out.

[drail]

Double check every step of the reloading process. Stick with data from loading manuals and work up slowly. I strongly agree with using a single stage press and loading blocks. I have seen many guys get into trouble using progressive presses because they weren't paying close attention and it's so easy to miss something when there's four or five things happening at once. Visible pressure signs are not really helpful because by the time you see them you're already over safe working pressure for certain guns. Have a good light source and no distractions when reloading. It is a fun safe hobby but there is very little room for error.

[SL1]

because the working pressures and action types are not the same. Also, the primers are not the same.

Primer cups for pistol primers are usually softer than primer cups for rifle primers, but at the 35,000 psi pressure limit for the 9mm Luger (or even the 38,500 +P pressure limit), it is not guarnateed that all makes will show "too much" flattening at the pressure limit.

And, hard extraction of fired cases is not something that you are going to find in an autoloader. Marks on the case heads don't really occur until the pressure is way to high for an autoloader.

Split cases can be a brass issue instead of a pressure issue (age or poor manufacture). The appearance of firing pin indentations on the primers can be altered by a lot of gun issues.

So, thre is not much other than the way the spent cases are ejected to give you an idea of how hot the loads are. And, that is only good as a relative indicator when the powder burn rate and bullet weights are about the same. It is entirely possible to get a much higher pressure with a fast powder and a heavy bullet and still get about the same ejection characteristics as with a light bullet and a medium burn-rate power.

A choronograph will help you recognize if you are getting more than the "expected" velocity for a particular load. But, that is not an exact tool, because different guns vary enough with the same load that their velocity differences would seem to imply some pretty large pressure differences. For example, a QuickLOAD calculation I just did for another thread showed only a 60 fps velocity difference for an 11,000 psi pressure difference in a 9mm load (due to a 0.056" change in COL). But, it isn't uncommon to find two guns that shoot the same load with velocities that differ by 60 fps, and it is NOT clear that the only gun differences that matter to velocity are the ones that also matter to the peak pressure.

You could measure the pressure rings of your fired cases to get some idea of relative pressures in different loads. But, again, that is not a very precise method, and is subject to a lot of complicating factors that can be misleading if you try to work-up loads to maximum by aiming for a particular pressure ring measurement. You would need to research the method, test it in your gun, and practice with it before it would give you much real benefit.

Case head expansion measurements aren't much help at auto-loading pistol pressures.

What I do with autoloading pistols is stay within published maximums from PRESSURE-TESTED data (not just what somebody else has survived and published on the Net). And, when I need to change bullets or seating depths from what was used in the published data, I use QuickLOAD to help me adjust the charges from the data, after first "tuning" the QuickLOAD parameters to my gun/bullet/powder to match published data. Rules of thumb for such adjustments and cheaper programs like "Load from a Disk" can also be used with less precision.

SL1

[wncchester]

Stick to the book charges or a tad lower and all should be well.

The over pressure signs for rifle is almost totally lacking in handguns. Difficult extraction in revolvers is one, bulged case heads in some autos is another. Mostly, the only real sign of a slighly hot load in an auto will be battering the recoil system and that takes time to accumulate enough to see.

Fact is, within limits. book loads are likely to be safe as they are presented. I've seen book loads be excessive in rifles, never found any evidence of excess pressure with book loads in handguns.

No case can expand larger than the chamber walls so, in my experience, split case walls is only the result of normal reloading done too many times on that case. And, generally, split cases are harmless.

[micksis86]

Thanks for the info. I'd assumed that the signs would be quite different given the difference in operation. I don't plan on trying to load maximum charges at all I just wanted to know to make sure all is safe.

[rg1]

I've got a question to ask concerning pressure when loading autoloading pistols. When working up loads starting loads and mild loads sometimes only kicks the brass lightly out onto your shooting bench. Maximum book loads can eject fired cases out behind the bench 10 feet or more. Is ejection patterns of fired cases ANY indication of pressure say comparing it to ejection of factory rounds?
By the way I test loads over a chronograph and bullet speeds are my main indication of pressure levels. I agree that primer flattening etc. is a poor judge of pressure in a semi-auto pistol.

[80viking]

There are no reliable pressure signs in a semi-auto pistol, its best to just stick to the book.

[wncchester]

"Is ejection patterns of fired cases ANY indication of pressure say comparing it to ejection of factory rounds?"

As a general indicator, sure. But lots of things can alter that so it's not definitive.

[colospgsAVID]

I've loaded some high pressure rounds. Say well? over max loads and never have seen a flattened primer. I used the wrong powder(IE faster) once with a heavy bullet and the primer was flattened. This to me was an extreme sign of overpressure!

Needless to say I pulled the bullets of those rounds!

[colospgsAVID]

so as to not edit a post twice...I have had a ton a flat primers in alot of different .223 factory ammo. All of the .223 WSSM factory ammo I have fired have had way flat primers.

[steve4102]

There are no reliable pressure signs in a semi-auto pistol, its best to just stick to the book.

Stick to the book charges or a tad lower and all should be well.

What I do with autoloading pistols is stay within published maximums from PRESSURE-TESTED data

Good advice to be sure, but what do you do when the "Books" differ? What do you use for Max or "Start" for that matter, when you have load data from different sources with the exact same components and their Max and Start charge is way different. In some cases where a Max charge in one manual is a "Start" charge in another? What then?

Here is an example, 40 S&W. Speer 180gr HP.

VV data, 3N37, 5.9gr Start, 6.2gr Max, COAL 1.126
Speer #13, 3N37, 6.6gr Start, 7.2gr Max, COAL 1.120

Same bullet, same powder, almost same COAL, yet the "Max" charge for VV is less than the "Start" charge in the Speer manual. How do you stay within "Pressure Tested" parameters with discrepancies like this?

Thanks

[SL1]

Here is an example, 40 S&W. Speer 180gr HP.

VV data, 3N37, 5.9gr Start, 6.2gr Max, COAL 1.126
Speer #13, 3N37, 6.6gr Start, 7.2gr Max, COAL 1.120

Same bullet, same powder, almost same COAL, yet the "Max" charge for VV is less than the "Start" charge in the Speer manual. How do you stay within "Pressure Tested" parameters with discrepancies like this?

First, are you sure it was the same Speer 180 grain Hp bullet in the VV data? Differences in bullets, even different construction technologies by the same manufacturer, can produce bullets of the same weight that create different pressures. Cases used can also make a difference, and those weren't mentioned, either.

Second, assuming that these two data sources actually do use the exact same bullet, then what I would do is work to the velocities with my chonograph. That doesn't always make sense, either. You did not provide the velocities, so I don't know if they differed or not.

Why not post the velocities for these data and we can consider it further? It would also help to post the brands of cases used in for each data source and more specifics about the bullet(s).

SL1

[steve4102]

First, are you sure it was the same Speer 180 grain Hp bullet in the VV data?

As sure as I can be. According to my Speer manual and Speer's web site they only make one 180gr HP.

VV Data, Remington Brass, Primer-Small Pistol, Test barrel 5 1/2 inches 1-16 twist. 5.9gr 994fps, 6.2gr 1035fps.

Speer data, Speer Brass, Primer-CCI 500, S&W 4006 with 4 inch barrel 1-16 twist. 6.6gr 841fps, 7.2gr 960fps.


Just to through in some other data here is Sierra #5 data. 180gr JHP, 1.125,Brass-Starline, Para P-16 1-16 twist 5'' barrel, WSP Primer.
Start 6.2gr 850fps, Max 7.5gr 1100fps.

[SL1]

Also, unless the VV data says something like "Gold Dot" then it is not really clear if the two Speer bullets are the same, since Speer changed its bullet designs from cup-and-core to unicore, and usually put a smaller hollow in the newer bullets.

Give me the COLs and I will see if I can use QuickLOAD to deduce how much case volume difference would be needed to account for the data difference. Then we can ponder whether that much difference is realistic.

SL1

[steve4102]

COL, VV 1.126, Speer 1.120

[SL1]

Ok, if the bullets really are identical, then the COL difference is only 0.15 grain difference in water capacity. That is only a 2% difference in the available powder space, and it makes only about 1,000 psi difference in pressure.

The Speer max gives a pressure of 37,600 psi and 1100 fps with the QuickLOAD default case water capacity of 19.3 grains. I would have to take that to 23.5 grains to match the 960 fps velocity, and then the pressure would be down to 20,300 psi, NOT a likely max load. So, I have to wonder why the Speer max velocity is so low.

The VV max load gives a pressure of 24,000 psi with the default case capacity, but velocity is 1015 fps, pretty close to the data.

The difference in case capacity needed to match these velocities is 4.2 grains of water, or a 22% difference. That is unrealistic, in my opinion, but maybe others have seem something like it.

The other probable difference is the powder lot. If I increase the burning rate by about 20% in the VV data, I get 33,900 psi, which is a reasonable max pressure, but then I also get a velocity of 1113 fps.

One thing to consider here is that the data sets we typically see in loading manuals are giving us an apples + oranges mix of information. The max charges are developed in a test barrel that has dimensions set to minumum SAAMI specifications so that the pressure will be as high as it should ever get in a production gun. But, then the max and start loads are fired in a commercial gun to give a more realistic idea of what the velocity is likely to be when we load for our own, larger than SAAMI-minumum chambered guns. So, the pressures that produce the velocities shown are not the same as the pressures in the test barrel, and typically give somewhat lower velocities.

There are a LOT of variables that I could adjust in QuickLOAD to try to match these data. But, even if I find a match, there is no guarantee that it is the only possible combination that provides a match, or that any other matching combinations would give the same pressure.

So, I don't know how to decide which set of data is most applicable to my particular gun and lots of powder and primer.

IF the two labs had used the same lots of powder as well as the same bullets, then I would expect that the test barrels would have given more nearly the same max charges.

So, I am guessing that we are comparing velocity data from two different lots of powders fired in two different guns with different sized chambers. This suggests that data produced with one lot of powder, when used for a different lot of powder, can make a pressure difference of more than 10,000 psi. And, guess what: QuickLOAD provides a standard warning at the bottom of its output screen that showes a +10% and a -10% change in the powder "Ba" factor as a caution for the uncertainty in its calculations, and, in this case, that is about 11,000 psi difference.

If this is making you nervous, I think that is the proper lesson.

SL1

[GP100man]

With todays availibility of info no wonder theres posts like this !!

I don`t load for many auto loaders but I use the average of three method , then start at START.

I feel very blessed that I can load 5 rnds. & stand on my porch & shoot em though & I can understand posts of this nature , especially at todays prices of components almost takes the FUN out!!