32 ACP / 32 S&W Long power differences

[Dan Forrester]

I just started reloading .32 ACP this week and stumbled upon something interesting.

My load consists of PPU brass, Berry’s plated 71 grain bullets, CCI primer and 2.0 grains of Bullseye. I’ve loaded and fired 50 rounds so far with no malfunctions out of my Colt 1903.

I had some old pressure treated deck boards set up in my back yard to do some penetration testing and the rounds out of the 1903 consistently went through 2.5 deck boards. I dropped a round into my 32 mag SP101 with a 3” barrel just to see if it would function. I have fired .32 ACP in this gun before and they always fire but I just wanted to check function with my reloads. The round once again fired just fine however it only went through 1.5 deck boards.

I though this was strange so I decided to load up a couple rounds of 32 S&W Long using the same CCI primers, 71 grain plated bullets and same charge of 2.0 grains of Bullseye. Well this load wont even make it through a single board.

So why is there such a power difference between the 1903 and the SP101 both with the exact same .32 ACP load?

And a follow up question is why is there such a power difference between .32 ACP and .32 S&W Long when the primer, bullet and powder charge are exactly the same?

Thanks,

Dan

 

[Englishmn]

Cylinder gap and the long bullet jump down the cylinder. Trying that load in a magnum case would still be lower pressure but probably better since the bullet travels shorter distance in cylinder.

 

[GeoDudeFlorida]

Cylinder gap and the long bullet jump down the cylinder. Trying that load in a magnum case would still be lower pressure but probably better since the bullet travels shorter distance in cylinder.

And the .32Long is a much larger case than the .32ACP, which is not roll crimped either by the way, further reducing pressure and yielding a slower bullet. Bump the charge up to 2.8gr Bullseye, put a nice even roll on the case mouth and see how the .32Long does.

 

[Dan Forrester]

I always thought cylinder gap and bullet jump was more of an academic consideration and didn’t really factor into real life shooting. Guess I was wrong.

Thanks for explaining all this to me.

Dan

 

[Walkalong]

cylinder gap

Can make a big difference. Some are tight, some are huge.

 

[P Flados]

Also, the bullet and case on a 32 ACP are both pretty short. As the bullet base just leaves the case, there is probably a lot of blow by before the bullet seals off the gas when it engages the throat. Given the small amount of propellant in a 32 ACP, blow by and cylinder gap result in a notable percentage loss.

 

[EricBu]

Well, I'll shoot 32 ACP out of a 32 H&R or 327 Fed, but a lot of 32 Long pistols, especially top breaks, will turn into rattle traps if you do it. I generally consider 32 ACP too hot for longs myself, but gawd knows plenty of folk shot it in the old long revolvers. What's interesting is shooting 32 acp out of a revolver with the same barrel length as a pistol.....then you really see the difference that cylinder gap makes...it'll shock you.