What would be the best twist rate for a 375 x 2 1/2" flanged Nitro Express? I have the choice of 8 or 12:1.

Roger

12:1 is standard for the typical .375 bullet weights.

I have always used a faster rate when ever I Had the choice.

OK, What is the worst that can happen if I go to the 8:1?....I only intend using either 270 or 250 grainers.

Roger

You may develop too much pressure. Every .375 out there,_9.5x56 mannlicher to the .375 Dakota spec's a 1:12 twist. Holland & Holland used a 1:16 twist on their .375 flanged magnum, I believe to keep the pressure down for double rifles. If you use the 1:8" barrel, let us know how it works out.

OK, Another twist rate question, different calbre/cartridge...would a 1 in 10 be too fast for a 32-40?
I have a Martini cadet with a 303 British barrel chambered in 32-20 and I was thinking of re-chambering to 32-40 and using 150 grainers.

Roger

Winchester 94's were 1:16 I believe. My old Lyman 45th ed states that. The twist is only too fast if you load it to high velocity and it won't shoot or is dangerous to the shooter and the gun.

I have a Mauser with a 7x57 bbl that has a 1:8.5 twist designed for 175 gr bullets. When you load up 139 gr bullets and drive them fast, it doesn't group well. But if you load it moderately, it is sub-MOA. The accuracy point is around 185,000 rpm. The hotter loads were 250,000 rpm.

quote:

Originally posted by yumastepside:
OK, Another twist rate question, different calbre/cartridge...would a 1 in 10 be too fast for a 32-40?
I have a Martini cadet with a 303 British barrel chambered in 32-20 and I was thinking of re-chambering to 32-40 and using 150 grainers.

Roger

For the 32-40, if you are planning to only use jacketed bullets 1 in 10 will be fine. If you ever want to use plain lead bullets, that fast a twist may cause them to strip in the rifling.

Out of a Martini, I'm thinking medium velocity jacketed and hard cast.

Roger

Definitely not 8 to 1: and I know of no one making a 375 barrel with that fast of a twist, nor do I see any reason to.
What Steve said; 8 won't work with lead bullets.

Try and keep up Tom We're on to a different calibre

Roger

Crap; I never read the questions before I answer; saves time that way.

Just read of a new sub-sonic 338 round that uses a 1in3 for 300gr 338 match kings

I recommend going with the standard twist rate, my only concern would be if you wanted to use Woodleigh 350g bullets. I would call Geoff and ask his advice as to twist rate.

My 500 Jeffery has a 1 in 10" twist McGowan barrel. If I load my 570g bullets faster than 2400 fps I can literally feel the forearm twist in my hand. It's very accurate and at a sedate 2300 fps I don't seem to feel it twist at all. If I had to do it again I would go with a slower twist rate barrel.