gas length question - search failure

[calicojack]

tried doing a search. maybe my search-fu is weak, but i couldn't find the answer.

can someone please explain to me, in layman's terms, the difference between carbine length and mid-length gas?

[bkb0000]

though there is a vast over-abundance of information, especially recently, on this topic, M4C search engine rejects the word "gas," as a three-letter word, so it's probably a little tricky to search for it. if you click "advanced search" on google, you can search this site specifically for whatever terms you want.

carbine gas: 7.5 inches from the barrel nut- used on basically all SBRs, and most 14.5 and 16" guns
mid-length: 9.5 inches- used on some 14.5s, more 16.1s, and some 18" guns
intermediate: 11.5"- used on Noveske 18" guns, and i think.... KAC? cant remember who the other manufacturer is that uses this, or a very similar, gas length
rifle: 12.5"- used on more 18" and basically all 20" or longer guns.

[Belmont31R]

Carbine is roughly 7" and mid length is roughly 9".


Carbine is more of a jab and a middy is more of a push recoil wise. I find its easier to stay on target with a middy gas system than a carbine all else being equal. They are just softer shooting guns in general. Carbines still have their place but for just recreational shooting, classes, general purpose, etc a middy is a better option.

[skyugo]

tried doing a search. maybe my search-fu is weak, but i couldn't find the answer.

can someone please explain to me, in layman's terms, the difference between carbine length and mid-length gas?

a mid length's gas port is closer to the muzzle end of the barrel.

the carbine length was originally developed for 10.5 barrels i think, then they slapped a 14.5 on there and called it the m4 carbine. the gas pressure and timing in carbine length is not really ideal. with the proper buffer and spring it can work reliably, but tends to beat up bolts more than midlength or rifle length .

[calicojack]

Carbine is roughly 7" and mid length is roughly 9".


Carbine is more of a jab and a middy is more of a push recoil wise. I find its easier to stay on target with a middy gas system than a carbine all else being equal. They are just softer shooting guns in general. Carbines still have their place but for just recreational shooting, classes, general purpose, etc a middy is a better option.

awesome responses. thanks guys. you cleared it up for me.

[Chameleox]

One more question:
Why don't you see more SBRs around the 10.5 and 11.5 range with mid-length systems?
Just getting into NFA and I'm curious.

[LOKNLOD]

One more question:
Why don't you see more SBRs around the 10.5 and 11.5 range with mid-length systems?
Just getting into NFA and I'm curious.

Because there isn't really room for a FSB or gas block in the midlength position on a barrel that short. 10.5" is about the shortest you can do with a carbine system, so I'd say 12.5" is probably the shortest you could build with mid-gas. And that's just based on the dimensional limitations. Length of barrel between the gas port and muzzle is a very critical dimension. As the barrel and gas system get longer, it becomes even more sensitive to having proper dwell time and gas port sizing.

[bkb0000]

One more question:
Why don't you see more SBRs around the 10.5 and 11.5 range with mid-length systems?
Just getting into NFA and I'm curious.

the weapon would be very unlikely to operate at all if you tried to go mid on pretty much any SBR.. dwell is necessary for a weapon to function, and if you put 9.5 port on a 10.5" weapon, you'd have basically no dwell.

the 14.5 mids are barely in the realm of reliably functional- and thats actually what makes them nice.

[Chameleox]

I'm smarter today because of you guys. Thank you.