Ar15, IMR 4064, and 14.5" barrel

[silverjay]

I worked up a load with 62 grain NOE GC boolits that cycles and shoots great out of my 16" ar. When I run it through the 14.5" ( pinned and welded) it is short stroke and double feed city. Hotter ammo (factory) runs the 14.5 fine. 4064 just too slow for the shorter barrel? Trying to walk the load up and see if that helps today.

[Jailer]

It's a timing issue.

A carbine gas system has the gas port in the barrel closer to the receiver allowing the expanding gas to reach the carrier sooner and the gas pressure pulse lasts longer due to the increased distance the bullet travels in the barrel after it passes the port compared to a mid length system.

Everything else being the same, for proper functioning it requires more gas pressure in a mid length since the pressure pulse arrives later and last a shorter duration than it does in a carbine length system.