[41mag]

& compared it to the cold barrels' bore diameter to measure just how much difference in size heat can distort a bore?

I recall from my physics classes that heat causes things to expand.Duh!
I also recall that a cylinder(rifle barrel in this case)will expand ALOT more towards the outside.That there will be some small,but measurable expansion(?)inwards however.

I'm guessing that there is a big enough fudge factor built into the barrel that the very slight constriction has no visible effect?

 

[andy]

another variable is HOW hot? 5 rds in 5 minutes? 5 rds in 5 seconds? 50 rds in 30 seconds?

 

[41mag]

another variable is HOW hot? 5 rds in 5 minutes? 5 rds in 5 seconds? 50 rds in 30 seconds?

That's true.Bore diameter,projectile mass,projectile composition,& all the same powder variables would have an effect.
Yikes!

It seems like there likely is no fast,cheap,& easy answer to this one.

 

[andy]

no, but you can go with what WINS high power rifle matches, the great majority use the AR in 223.

 

[GBullet]

The bore size will increase when the barrel is heated. Fortunately, the pressure on the base of the bullet is more than sufficient to expand the bullet to grip the rifling.