Large Caliber Barrel Twist

[frosty]

If I were going to make a barrel in 75 caliber, I would twist around 1-80" for a patched ball. The reason being, the grooves are space for patch material, ease of loading, and to eliminate random flyers when shooting. I wonder if a faster twist, say 1-48", would stabilize the ball, or do more harm than good? The rule is, the larger the ball, the slower the twist...

 

[tkendrick]

1-48 is way to fast for round ball in .75 caliber. I would argue, based on my experience that it is almost to fast for a .45, even though a lot of the commercial builders use it. The larger the ball, the slower the twist is absolutely right.

 

[ED21]

The rule is, the larger the ball, the slower the twist...

That has always been my understanding. The slower twist would possibly work for conical bullets but not patched round balls.

What style of rifle are you building?

 

[tkendrick]

The slower twist would possibly work for conical bullets but not patched round balls.

Actually I think you'll find that conicals are going to require a faster twist than patched round ball.

I have an early T/C Hawken that was set up for use with the REAL bullet, and has a 1 in 28 twist.

Handles about any of the conicals and sabot rounds I've tried, but absolutely will not shoot round ball accurately, no matter what patch/ball/charge combo you try.

 

[Orr89rocz]

you spin a ball fast, it will curve lol thats how you throw a curveball.

slow twist for balls. conicals are more like a football and will need quicker spin rates

 

[Loyalist Dave]

The slower the twist, the less disagreeable the torque due to recoil, but the Germans long before the birth of the American Long Rifle had long barreled target rifles with very fast twists. The only set rule is that the ball must rotate 1/4 turn (25%) before exiting the barrel. Hence the British Baker rifle with a 30" barrel was made to that spec by rotating the ball 1/4 turn for its length, giving it a 1:120 twist rate. (They also thought it would foul less per shot allowing more shots before wiping the bore - good idea for a military rifle.)

From a 1/4 to a 1/2 twist is fine, so a 1:48 twist would give you a 50% rotation in a 24" barrel. But if you had a 42" barrel a 1:70 twist rate gives you a 40% rotation, also just fine.

LD