Why is the 14.5 Mid better than 16 Mid?

[ra2bach]

I'm not talking about barrel length issues. my interest is in function. I always thought the mid-gas was optimized on a 16" barrel.

I'm looking to find out why the 14.5 Mid is better than the 16" Mid or even a 14.5 Carbine.

are there advantages other than handiness and velocity, or is it something else?

[Byron]

Gas ratio / dwell time:

https://www.m4carbine.net/showthread.php?t=54940


14.5 carbine - 52%
14.5 mid - 65%
16.1 carbine -47%
16.1 mid - 59%
18 mid - 53%
18 intermediate - 64%
18 rifle - 69%
20 rifle - 63%

[ra2bach]

Gas ratio / dwell time:

https://www.m4carbine.net/showthread.php?t=54940

excellent response, thank you.

so assuming that the 20" rifle has always been considered the benchmark, it seems that somewhere around 60-65% is optimal. or is higher better?

at what point does it go the other way with too little gas?

[uscbigdawg]

I can't give you a "technical" answer, but all things being equal between my 14.5" Mid and my 16" Mid that the gas impulse is not appreciably (if any) different. The 1.5" savings in length comes in handy occasionally for tight spaces and the velocity loss is negligible.

Rich