It does. It just doesn’t increase chamber pressure.
Maximum chamber pressure is achieved long before barrel twist is in play.
A long throat, shallow lead and Gain-Twist 5R rifling is not going to make up for 20 grains of powder.
In a 450 Bushmaster AR, the friction down the barrel has a lot to do with how much gas the bolt carrier gets. Bullet bearing surface and twist rate can affect the function of different rifles gas systems based on this increased friction, which robs only slightly velocity, but increases system pressure dramatically.
But this would not increase chamber pressure. Max is max. The throat diameter, length and lead angle would be more influential than the twist for
chamber pressure.
In my limited experience. Which is...
I have a 1/14” twist Bushmaster barrel. Because of the increased dwell time in the barrel past the gas port, in reality a minuscule longer amount, a conservative load is incredibly harsh on the rifle.
By the time I removed the burrs from the port (a gauge would insert but not drop through, it would have eroded away anyhow) and lightened the spring and buffer to achieve function, it was too much to move higher in charge weight. I bought a new spring and replaced the weights back into the buffer.
Though I don’t quite make the book speed.
I ran back up to the lowest maximum book number, without a single hint of problems.
45 caliber Varmint Rifle Bliss was attained.
Because I always thought this had more to do with the pressure on the bullet.
A faster spun bullet will have a more dramatic effect on impact than a “more traditionally” twisted bore.
A fast twist will also disintegrate some lightly constructed bullets with too much centrifugal force for the jacket. Or it may “strip” a lead bullet in the bore.
But none of this will have an effect on the maximum chamber pressure. You know, more or less...
Is that what you mean,
@Howland937?
