Gain Twist Yay or Nay

[rookhawk]

Thanks for the education, I'd never heard of this term before either.

All I know about 6.5x55 and 7x57 is the twist rate isn't the big deal, its having a long throat. Those 160gr 6.5s and 175gr 7mm bullets are what made the stuff of legend in a hundred years of safari literature. Make sure they like to shoot the big-uns!

 

[Bob Nelson 35Whelen]

Cause you’re not a phone, Bob.

@Josh P
If'n y'all want to know about P14s and M17s just ask and I will try and answer you
Bob

 

[Academic]

From a purely academic point of view my observations are as follows - if you try to force a bullet down a barrel with a tight twist - just as an extreme example think of 1:100 - in the same way a common screw resists being pulled out of a piece of wood - the bullet will resist going down an extremely tight twist barrel and pressures will go extremely high - and the jacket might tear - just like in a barrel that is too small or screw tearing out of wood. The screw will be easier to pull out of the wood if the twist is 1:2 whereas if it is 1:200 it will tear the wood before it comes out. Theoretically, a progressive twist barrel will get the bullet spinning before it tightens up to a tighter and tighter twist. The lower twist at the beginning would allow lower initial pressures, and as the burning chamber expands with the bullet going down the barrel the lower pressure remains stable or decreases as the twist rate increases.

I think the progressive twist makes theoretical sense if you are trying to either keep pressures lower with a very tight final twist; and/or keep a bullet jacket tearing with a very tight final twist.

 

[BANDF]

Hornady has an extremely good podcast about gain twist barrels. Gain twist isn't something particularly new, and it's often used on auto cannons (bore diameter typically above .50 cal) to avoid stripping driving bands and so on.

Highly suggest watching the podcast, it covers loads of technical information as it pertains to gain twist barrels.