Can a rate of twist be too fast for a pistol caliber cartridge?

[corbinace]

I am considering using an existing 0.308 rifle barrel with a 1:10 twist for a 32 S&W Long or 32 Long Colt.

This will be a stub on an H&R action.

I believe the 32 LC had a 1:18.75 twist and the 32 S&W had a 1:16. I see a Douglas barrel in 1:14 mentioned on the CVA site.

My limited knowledge says if you want to shoot a heavier bullet, you spin it faster. But what about spinning it up too much, is there such a thing in the Pistol caliber speed zone?

Speeds will fit inside 600-1000fps, likely in the 7-800 range, but who knows?

This caliber normally is 75-100gr area but I may venture outside those numbers just for the knowledge gained.

Please chime in with your thoughts, even it is to say stop right there.

[Recycled bullet]

I think your idea is really interesting. Have a look at some standard rate of twist and bullet weights for 300 blackouts 1-7 twist handling 110-230 grain bullets.

[atfsux]

The necessity of faster spin rate has to do with how long the projectile is and how rear-heavy vs. the nose. A short and stubby wadcutter, for instance, does not REQUIRE a fast spin.

But that is not the question.

The question is whether the faster spin is DETRIMENTAL to a shorter pistol type bullet that typically does not require such a fast spin. And I think the answer is dependent upon what material will be interacting with the rifling.

If you plan to shoot plain soft lead,...yes,...I think the spin might induce too much stress to the bearing surface at some unknown velocity threshold and cause the soft lead to strip itself from the rifling and fling sloppily downrange. However, if it were a copper jacketed bullet, I suspect there would be no issue at all. The mystery would be what combination in between those 2 extremes can still produce desired results. Would a powder-coated cast projectile of 16 BHN (typical "hardball" alloy) work fine? I don't know. Experimentation would be required to learn the answer.

[GhostHawk]

I agree with atfsux but suggest that a gas check design should remove any worry.

OP I love the .32sw long and yours should make a great little woods walking gun.

You also have the option of using a .32 H&R mag chamber reamer which lets you play with even more options.

[Jedman]

I have built several 32 S&W long rifle barrels and a few chamber adapter inserts with 30 cal. 1 - 10 & 1 - 12 twist and they shoot .312 100 gr. cast lead great. I just shoot them at standard velocity and don’t try to really push them. That’s the beauty of a light loaded 32 no noise, no recoil, and they kill small game well without meat damage.
Jedman

[Outpost75]

I have rifles in .32 ACP, .32 S&W Long and .32-20 John Taylor fabricated with .308, 4-groove, Govt form barrels with 10-inch twist. All shoot well. Especially with minimum velocity "Cat Sneeze" loads. 180-grain blunt cast bullets are quiet and accurate with the lightest charges which will exit the barrel, about 500 fps. Accuracy with common factory equivalent loads is not impaired. I also have a .38 S&W rook rifle assembled with a 10-inch twist 9mm Luger blank which drives bugholes firing 240 grain bullets at 500 fps, being quiet like an air rifle. No can needed.

[corbinace]

Thank you for your responses Gentlemen.

I do usually cast a harder alloy and do powdercoat, so that is looking like a help here.

I intend a very modest power factor so fast is not a requirement. Though I would prefer as flat as possible out to about 50 yards.

Quiet and 50 yard accuracy is my main goal, so it looks like I have enough reason to proced.

[Larry Gibson]

With the short stubby pistol cast bullets if you keep the velocities under 1100 fps accuracy will be fine. I shoot many such bullets out of 10 and 12" twist 30/31 caliber rifles all the time. Also, my Contender 32 H&R barrel has a 10" twist. Same with it, keep the velocity under 1100 fps and cast pistol bullets shoot fine.

However, if you can find a 308W Palma barrel with a 13 or even 14" twist it would be much better. Most such Palma barrels were 27 - 30"+ long so even if the throat is shot out for Palma accuracy there's still lots of good barrel left. Not too hard to get a good barrel out of the muzzle end 24 +/- end of the barrel.

[Driver man]

I have a friend who shoots a GSP pistol with a barrel machined down from a worn 308 rifle. It shoots HBWC or DEWC with 1 hole groups using a Ransom rest. The twist rate is 1:10.

[Rapier]

The 32-20 single shot handgun barrels, TC, Merill, RPM, MOA and BFs all have .308 1-10 twist barrels. The original Ruger Mini-30s chambered for the 7.62x39 were the same, had a .308 barrel with a 1-10 twist.

My 7.62x39 AR-15s all have .308 barrels with 1-10 twist so I can shoot 150s in them with 1680. I fully intend to make a joyful noise, just the other end of the rainbow.

[dtknowles]

The fast twist will be fine for your application. Over spinning at higher velocity can have a detrimental effect on accuracy but at your lower velocity and not needing benchrest accuracy, you should be fine.
Tim