
Originally Posted by
Clint
Actually, 11.5-12.5" is best for a carbine length gas system.
IIRC, the CAR was developed for the Colt Commando with 11.5" barrel.
With any given gas system, a longer barrel has the most gas drive available.
"Gas drive" is the area under the pressure curve, PSI x SEC is an appropriate unit.
Also note that pressure is still useful for several milliseconds after the projectile has left the bore.
Compared to a 16" MID, a 14.5 CAR has roughly 35% more gas drive available, while a 14.5 MID has roughly 12% less gas drive available.
As long as plenty of gas drive is available, the gas port size makes the biggest difference in the operation.
For example, a 16" CAR with a .060" port will run much better than a 16" MID with an .093" port.
In this case the CAR is properly gassed and the MID is way over gassed.
By an an absolutely amazing coincidence, the 14.5" barrel uses the standard CAR 15 gas tube and mounts the standard M16 bayonet.
Dave
INNOVATION IS SELDOM ACCOMPLISHED WITHOUT CONTROVERSY.
My first rule of a gunfight, thanks to John Farnam's wise advice. "Get away from there!"
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