Anyone ever use .32 ACP brass in place of .32 S&W?

[TruthTellers]

This is something I've been wondering about for a bit and I'm not talking about loading .32 ACP to .32 ACP pressures, I'm talking about using it in place of .32 S&W cases and using .32 S&W load data and lead bullets.

Just wondering as the .32 ACP Lee die set I have says it's for both .32 ACP and S&W and both cases have a similar OAL and both headspace off the rim in a revolver.

If you can't tell by now, I have a fair amount of .32 ACP brass.

I don't have a .32 S&W (short) revolver, but I've always had in my mind somewhere about getting an 1863 Pocket and a conversion cylinder which uses .32 S&W. Also, there are still a lot of top breaks out there real cheap that use the short .32 S&W and if a good deal came around, I wouldn't want to say no just because the brass is not common.

[mcb66]

I see no reason why it wouldn't work. I've short plenty of acp in my 32 revolvers.

[zxcvbob]

I think the ACP has a thinner rim. That could cause light primer strikes, depending on the gun. Try it and see if it works for you

[FrankenMauser]

CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.
Obligatory warning, since this subject involves doing things that every reloading manual tells you not to.

I don't know why it worked out that way, but...
I load .32 S&W with .32 Auto data. And I load .32 Auto with .32 S&W data (on the very rare occasion that I load .32 Auto).
*All of my .32 caliber cartridges are fired in modern revolvers.*

Check case capacity before you load, though. Some brands are notably different between .32 S&W and .32 Auto; and low case capacity cartridges tend to spike quickly as pressure increases.

[gwpercle]

The 32 acp is actually semi-rimmed . In revolvers with chambers in good condition , not overly large and not too worn the little rim will usually offer enough support for the 32 acp to be fired in the 32 S&W chambers. I'm not sure if this is safe or not but certainly the 32 acp cases can be resized and 32 S&W data used .
Lot easier to come by 32 acp that's for sure !
Gary

[Unclenick]

Based on QuickLOAD's database, the 32 ACP has 9.25 grains of case water overflow capacity, while the 32 S&W has only 5.40 grains of case water overflow capacity. Even seating bullets to the same COL, the 32 S&W case has almost 30% less water capacity for the powder to fit into. This means it has a thicker head or thicker sides near the head than the 32 ACP, and with that greater confinement, it is expected to produce significantly higher pressures with the same load.

In QuickLOAD, using the default settings, if I put the same XTP bullet in both cases with the same COL and put enough Bulleye in to run the .32 ACP at 10,000 psi, less than half its rated pressure of 21,000 psi, then substitute the 32 S&W case but seated the bullet so shallowly it had the same COL as it did in the 32 ACP, the pressure prediction jumps from 10,000 psi to 16,000 psi, which is close to the SAAMI MAP of 17,000 psi for the 32 S&W. The bottom line is that you can put 32 S&W loads in the 32 ACP and expect very light target or plinking load performance, while a maximum load in the 32 Auto loaded in the 32 S&W with matching COL would produce about 40,000 psi, or about 2.5 times SAAMI MAP for the cartridge.

Because of the above, FrankenMauser was right to post the load warning. Even if, due to chamber dimensions or throats or, most likely, the primer unseating the bullet ahead of full powder burn getting underway, we need to recognize the computer prediction could occur in some guns using some powders, especially with a strong crimp on the 32 S&W case, and declare this idea a bad practice in general.

[TruthTellers]

Well, my question wasn't about loading .32 S&W to .32 ACP load data, but loading .32 ACP with S&W load data producing a very light target load is exactly what I would be looking to do for any .32 S&W (short) revolvers, just not have to get new brass to do it.

Nick, since you have the fancy software, what if the .32 ACP case was trimmed to the same length as .32 S&W and standard .32 S&W load data was used? What kind of pressures would it be?

I figure I ask because there's always a chance that an ACP case won't be able to chamber in the cylinder due to bottoming out at the start of the throat.

[ligonierbill]

I dug out my H&R Topbreak, made sometime prior to 1904, and tried empty cases. Yes, the 32 Auto bottomed out, standing about a tenth (didn't measure) of an inch above the 32 S&W case. I did not try to close the pistol, but I think it would interfere. In addition to being longer, the 32 Auto case has a thinner rim than the old S&W. I believe they would work if the case were trimmed.

FWIW, Midway has Starline brass for .18 apiece right now.

[Unclenick]

Well, it turns out a lot of what I wrote in post 6 is probably wrong. The QL database commonly has handgun cartridges at a little short (around ½ to 1 grain) of average case water overflow capacity in order to make pressure err slightly on the high side, hoping to limit risk-taking. However, today I found a 35-year-old box of Remington 32 S&W with empties inside, so I was able to measure the case water overflow capacity and found it was 8.2 grains in a case that was 0.5925" long. If it were the 0.605" SAAMI maximum length used in QuickLOAD, the capacity would be 8.44 grains, not the 5.4 grains in the QL database, a 3.04-grain difference, which is a lot in this little case. I also located an R-P .32 Auto case that was 0.6705" long and had 9.8 grains case water overflow capacity when I measured it. Its capacity, if it were a full 0.677" long would be 9.924 grains of water. Both cases are not resized, so this is as-fired, but the main point is that if I shortened the 32 Auto to match the length of the 32 S&W, it will have 8.53 grains of case water overflow capacity, which is so close to 8.44 that if I had larger samples to measure we might find the difference to be in the noise of case-to-case variation. In other words, negligible.

The bottom line here is, I don't know your particular case's exact capacity, but it is looking like substituting a cut-down .32 ACP for a .32 S&W is perfectly safe and reasonable to do if the cases are R-P. It may also turn out to be true in other brands.

[TruthTellers]

Nick, that's really cool to hear, but you're right in different brand cases would likely have different capacities. I figure that Starline would be the most sensible brand to compare the .32 S&W and ACP cases given it's the only company I know of today that makes brass for .32 S&W.

The only issue would be in .32 ACP because there are a lot of companies that make ammo in that and their cases will all likely be different, but they'll all likely be so close that it will be a negligible difference. I mean, if anyone were to seriously be loading trimmed .32 ACP to .32 S&W load data, I would have to believe they'd be starting at suggested starting load data and working up from that.

I can't say this is something I may ever do given that .32 S&W brass is easy to get, I was wondering about this as a proof of concept. Who knows how much longer Starline will continue to make .32 S&W brass.

How are you measuring this "case water overflow" capacity?

[Unclenick]

You plug the primer pocket. I used to use clay or put tape across the bottom, but the former was messy and the latter would often leak. The easiest thing, if a fired primer isn't already in the bottom, is just to seat a fired primer back into the pocket. This assembly is weighed dry. I then use a squeeze bottle of water with a spout to fill the case until the water is just level with the case mouth with no meniscus. That last thing can be hard to achieve, so I commonly wind up going a little over until the water has a slightly rounded meniscus that isn't overflowing the case but is above the edge of it and then twisting the corner of a tissue to a point and using that point with a quick in-and-out motion to flatten the meniscus until the top of it is level. After making sure no water drops got on the sides of the case I weigh it again. I subtract the dry weight from the wet weight. Since my water bottle sits out in my basement at room temperature of about 68°F, I divide the result by 0.998 to compensate for the lower density of water at that temperature, but it seldom makes enough difference to matter a tenth of a grain. It's mainly a habit.

The case length has to be measured to know how a maximum length case would compare. The difference between the two numbers is just pi×r²×length difference between your case and the nominal case length, which is maximum under SAAMI spec methodology.

The number you wind up with is Case Water Overflow capacity. This is distinct from Case Water Capacity, which, without the word "Overflow" included, refers to the water capacity under a seated bullet (the powder space). Obviously, Case Water Capacity by that definition differs by bullets size and COL, where Case Water Overflow Capacity does not.

Note that for QuickLOAD, the most accurate peak pressure predictions require the Case Water Overflow Capacity of an as-fired case from the chamber the pressure is calculated for if the peak pressure is around 30,000 psi or higher. The Case Water Overflow capacity of a resized case is generally more accurate for rounds producing peak pressures lower than that.

[FrankenMauser]

Huh...
I swear I responded to your initial post about the QL capacities, questioning how accurate they were (the QL data, not you).
But, it appears to have not worked. That, or I was dumb and never hit "submit".


Edit: Yea, it was probably my fault. I just hit 'back' on my browser twice, after typing this, only to realize that I never posted the reply.