AR15.Com Archives
 MId length vs. carbine length gas tube
marco223  [Member]
9/29/2010 8:34:34 PM
I'm about to build my 2nd rifle. And I'm choosing between mid length gas tube vs. carbine length gas tube on a "16. Does the mid length have a significant advantage? Thanks!
survivorman  [Team Member]
9/29/2010 8:38:47 PM
supposed to be a little more reliable and a little less felt recoil....if you think 5.56 kicks hard I guess. Carbine will weigh a little less
boomhower1820  [Member]
9/29/2010 8:59:50 PM
A little less felt recoil, supposedly a bit less wear and tear, more rail space with a fixed front site.
EdgecrusherXES_45  [Team Member]
9/29/2010 9:06:32 PM


This gets discussed once or twice a week still.
You have some who will say one is better than the other. Both work that is what it amounts to.
TonyAngel  [Member]
9/29/2010 9:13:20 PM
I've had both. Go with the mid length. I wouldn't say the difference in recoil is negligible. You may not notice it shooting off hand, but you sure will notice it shooting for a bipod in terms of getting back on target for follow up shots. If someone gave me a 16" carbine, I'd take it without griping. If I had a choice, it would be the mid length all day long.
EMSflyer  [Team Member]
9/30/2010 7:34:24 AM
I have a Sabre mid length upper and I really like it.

If you are going to get a 16" barrel then for sure I would get a mid length.
Maxwell600  [Team Member]
9/30/2010 11:13:08 AM
Originally Posted By EMSflyer:
I have a Sabre mid length upper and I really like it.

If you are going to get a 16" barrel then for sure I would get a mid length.


this.
hell, 14.5 get a mid
Gregory_K  [Team Member]
9/30/2010 12:03:22 PM
Originally Posted By boomhower1820:
A little less felt recoil, supposedly a bit less wear and tear, more rail space with a fixed front site.


I have a carbine gas system and as much rail length as a rifle. With a std A2 FSP.
Rosebudteg  [Team Member]
9/30/2010 1:01:44 PM


Oh crud... now you've done it.

In all honesty, it seems to be a matter of opinion. I've looked at all the stuff about this on ARFCOM and I've decided that mid-length is right for me.

Crud... there is a great thread about the pressures created at different lengths in the AR and dwell times and blah blah blah but I can't find it. Can anyone else find that thread with the cool graphs and whatnot and post it here?

edit: Nevermind, I'm finding them now.

How Does the AR Gas System Work?
FMJ  [Team Member]
9/30/2010 2:21:35 PM
Originally Posted By survivorman:
supposed to be a little more reliable and a little less felt recoil....if you think 5.56 kicks hard I guess. Carbine will weigh a little less



What I don't get?
When did the M4 become unreliable?


goldeneye  [Member]
9/30/2010 2:59:29 PM
Originally Posted By FMJ:
Originally Posted By survivorman:
supposed to be a little more reliable and a little less felt recoil....if you think 5.56 kicks hard I guess. Carbine will weigh a little less



What I don't get?
When did the M4 become unreliable?




Exactly what I was thinking
DamageInc308  [Member]
9/30/2010 3:19:23 PM
Originally Posted By goldeneye:
Originally Posted By FMJ:
Originally Posted By survivorman:
supposed to be a little more reliable and a little less felt recoil....if you think 5.56 kicks hard I guess. Carbine will weigh a little less



What I don't get?
When did the M4 become unreliable?




Exactly what I was thinking


The fact that the middy is a design improvement does not make the M4 "unreliable". The M4 can perform just fine with the band-aids that have been developed for it. The fact is that the M4 is trying to extract before the brass has fully contracted in the chamber, which is why stronger extractor springs and inserts were developed to prevent the extractor from slipping off the case rim. That's also why broken bolts occasionally happen on M4s, but almost never on a middy or rifle. The midlength eliminates the need for those extractor band-aids by fixing it the correct way: extracting later in the cycle by using a longer gas tube. That doesn't mean that your M4 won't run well or that you should take it as an insult to your M4 buying decision. It just means that a better system has been developed, and you might want to consider the middy over the M4 the next time you buy.
kingoftheroad  [Team Member]
9/30/2010 3:26:09 PM
I like the midlength better, mostly because of the longer iron sight radius. If there is less recoil, I don't even notice.
RussellAthletic  [Team Member]
9/30/2010 3:33:00 PM
In terms of cycle rate in full automatic, I'm assuming a carbine length system would provide slightly faster rate of fire?
Drew1066  [Member]
9/30/2010 5:13:17 PM
Well, I follow the below rules myself (the M4 was designed with a 14.5 in. barrel and a carbine length gas system; however, many people want M4's with out making them SBR's and have 16 in. barrels on them):

Carbine Length = 14.5 in. or less

Mid Length = 14.5 in. to 18 in.

Rifle Length = 20 in. plus

Mid Length = smoother action on 14.5 in. barrels and above = easier to get multiple rounds on target
DansFlash  [Team Member]
9/30/2010 5:40:10 PM
Either one works great. I prefer the middy if it has standard hand gaurd lentgh. It's a more comfortable feel than the shorter carbine. If you are running longer rails it doesn't matter.
Fields_Overseer  [Member]
9/30/2010 6:29:34 PM
Originally Posted By Drew1066:
Well, I follow the below rules myself (the M4 was designed with a 14.5 in. barrel and a carbine length gas system; however, many people want M4's with out making them SBR's and have 16 in. barrels on them):

Carbine Length = 14.5 in. or less

Mid Length = 14.5 in. to 18 in.

Rifle Length = 20 in. plus

Mid Length = smoother action on 14.5 in. barrels and above = easier to get multiple rounds on target


the carbine gas system was designed for an 11.5" barrel. They just stuck a 14.5" in there for the m4. Since a new gas system was ever developed, they had to increase the buffer weight and extractor springs and inserts. A midlength is the correct gas system for 14.5 and 16" barrels (its perfected for a 15.something barrel so that its very close for both).

The same thing is happening now with 18"ers. mid and rifle gas is about the same amount off, so they invented the INTERMEDIATE gas system which is ideal for 18" barrels.
topgunpilot20  [Team Member]
10/1/2010 6:23:12 AM
I've owned multiple carbine and midlength rifles. For a 16" barrel, there is absolutely no reason to go with the carbine.

The midlength gives you extended sight radius, longer handguard, correct dwell time, and lower gas port pressure which results in smoother extraction, longer parts longevity, smoother recoil impulse, and less muzzle flip.

Anyone who tells you that there is not a difference between shooting a carbine and midlength does not have enough experience to be offering you any advise. The midlength gas system allows a skilled shooter to noticeably reduce split times between shots.

ETA: I don't see how this topic is a can of worms––there's really no argument for a carbine gas system on a 16" barrel.