AR question - carbine vs midlength gas system w/ 16" barrel?

[yuppiejr]

Hi,

AR guys - I'm relatively familiar with the concepts of the 3 main gas system lengths in the AR rifle (rifle, midlength, carbine/M4)... and that while the rifle was originally designed with a 20" "rifle length" gas system there were provisions made in CAR and M4 carbine design in the form of a heavier buffers and improved extractors to deal with the significantly higher pressures and bolt velocity. I've also read the after action reports of M4's catastrophically failing in the Iraq/Afghanistan conflicts after a few thousand rounds that some have attributed to excessive wear and tear on the internals due to the "violent" M4/carbine gas system + extensive full automatic fire in less than ideal environmental conditions.

My question is... given the typical consumer (no class 3, no SBR stamp, etc..) purchasing an AR is subject to the 16" barrel limit on their semi-automatic rifle, and that midlength gas systems are available for both 16" and 14.5" + a 1.5"+pinned muzzle device barrel lengths... why are the "carbine/M4" length gas systems so common/popular? From a manufacturing standpoint all the major and most minor brands make a midlength barreled upper... and in terms of parts cost it's literally just a couple inches of gas tube (pennies) and a change in the gas port hole (though the same for every barrel in the same batch). I simply can't come up with anything to make buying an AR with a carbine/M4 gas system worthwhile if a midlength is available for the same/similar price... or am I missing something? For purposes of this conversation I'm focusing on the M4/carbine vs midlength system and excluding rifle length systems with 18-24" barrels.

Pros of midlength - lower pressure/lower bolt velocity = less wear and tear on internals & greater overall reliability, longer sight radius, lower felt recoil and "jump" in the rifle.

Pros of carbine/M4 -it "looks" authentic?

Any insight would be much appreciated,

J

[Norsesmithy]

Carbine length is "milspec". For A2 style sights, it's got a calibrated battle zero.

But I agree with you. And anyone who's shot both (if they were of similar quality) knows that the 16 inch middy is WAY nicer.

[gyrfalcon]

...why are the "carbine/M4" length gas systems so common/popular?

Pros of carbine/M4 -it "looks" authentic?

Any insight would be much appreciated,

Do you generally like to answer your own questions?

[Dave Pendleton]

Jesus intended that the AR use a 20" barrel.

Don't make Jesus mad.

[Spartan117]

Carbines are common because people like guns that looks like M4s, and because companies have a lot of the supplies for these guns, i.e. barrels, handguards, gas tubes, etc. The 7" gas system was designed for an 11.5" bbl, there is no benefit to it over the midlength when used on a 16"bbl other than weight/balance. KAC actually uses an even longer (than mid) gas system on their 16" guns to achieve the ideal dwell time.

[JeepMJ]

I think the M4 is so popular because people like the look of military arms. Plus, Carbine carbine accessories are everywhere and are more commonplace than M16 style parts.

My 16" ARs had the mid-length gas tube. It made more sense since I used the 16" barrel but the A1 or A2 rifle stock. It was a surprisingly tight, light, and comfortable setup.

[goalie]

I was recently made a big fan of a middy-length with middy-gas system.