I once cut a 308 barrel back in 1" increments with a hacksaw and measured the velocity loss. It was about 25 fps/inch.
The significance of a test like that is that rules out the differences in velocity between barrels. I have seen a difference of 150 fps between "identical" barrels.
I recently made a sporter by cutting back an old target barrel to 20". My handload seemed rather fast, so I wanted to see how close it was to max, so i shot the same ammo in a 24" barrel. Velocity was not near Max.
24" - 2610 fps
20" - 2565 fps
Only 45 fps slower - about 10 fps per inch. Not much.
This is because the short barrel is much tighter bore - about .307. The longer barrel is about .308"
Caliber is 308 British. (A 303 chamber in a 308 barrel.)
The significance of a test like that is that rules out the differences in velocity between barrels. I have seen a difference of 150 fps between "identical" barrels.
I recently made a sporter by cutting back an old target barrel to 20". My handload seemed rather fast, so I wanted to see how close it was to max, so i shot the same ammo in a 24" barrel. Velocity was not near Max.
24" - 2610 fps
20" - 2565 fps
Only 45 fps slower - about 10 fps per inch. Not much.
This is because the short barrel is much tighter bore - about .307. The longer barrel is about .308"
Caliber is 308 British. (A 303 chamber in a 308 barrel.)
