[kitchen]

Just as an academic exercise mind you, if someone were to build an AR with collapsible stock and 14 inch barrel, with the intent to reliably feed and function a diet of SA ss109, IMI m855, and homebrew 69gr MKHP, where would one put the gas port? Would the carbine location be best, or go with an intermediate? Is there any other consideration, i.e., special buffer springs, specific compensator, etc.? Now, would the same choices apply to a 16” barrel, or is this an entire different situation?

[2111USMC]

I haven’t done any heavy wrench work on a black rifle since the days we only had one model (the M16A1E1). However, I doubt that the 2 inch difference between the barrel lengths would make any “appreciable” difference in available gas pressure or volume.

[smokingfrog]

You should be able to do a mid length gas system with either one and a H or H2 buffer.

Or a Spikes ST-T1 heavy buffer.

If you’re not shooting full auto, it probably doesn’t matter that much.

[MHGinTN]

The gas port hole on a 14" barrel is usually drilled by the provider of the upper. I have 'tuned' more than one 14 inch with piston and impingement systems by removing a small amount from the recoil spring in the buffer tube ... take a 1/4" at a time and check to see it cycles reliably. The last one I 'tuned' has a Osprey Defense piston kit on it, 14 inch barrel, and I had to remove approx. 1/2 of a coil to get it to feed without a hitch now after 550 rounds through it ... and still haven't cleaned it 'cause it don't crap where it eats. ;^)