Twist Rates

[22to45]

Gentlemen:
I have a 7 mm rem mag on a ross, which has a "Centurion" Barrel. I checked the other day, and it has a 10.5" twist. I know this is a bit slow in the 7mm diameter. It does stabilize 175 grain speer mag tips at 100 yards, I have not tried them at longer range. I am suprised how well it shoots after checking the twist rate. My question is: what are the limiting factors for twist rate?

If I was using a lower velocity cartridge would I expect less sucess with the slow twist rate?

Can I expect the heavy bullets to de stabilize at longer range as they slow down?

Thanks
Allen

 

[b72471]

Spin Rate on a slow twist barrel

Simply put, this is no different than what you see in a thrown football. The spin and release. If the spin is too slow it starts to wobble, for a short distance that may suffice but for long range there is no consistency. Soooo you will have to try this at different distances, to see what you have. In 7mm a 10 twist is not always bad. You also have the option of dropping to a lighter bullet. It should work out. Bill

 

[Eagleye]

Only 7mm's I can remember that were truly a problem were some early issue Schultz & Larsen 7x61 S&H that came with a 1-12" twist. They would scatter anything over about 150 grains all over the map, keyholes galore. I have loaded for two of these and used the 145 Speer Grand Slam with great results, since it is a shorter bullet. Your 1-10.5 should be OK with most weights. Some longer spitzer 175's might not be stabilized, but you would have to shoot them to find out. And as to velocity, yes, slower speeds will require slightly tighter twists for a given projectile. Regards, Eagleye.