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Posted: 9/27/2010 4:30:35 AM EDT
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Recently I completed a build. I went with a YHM 16" carbine length gas tube. It shoots just fine and runs like a top. Did get some feedback here when I started the build that I should use a midlength system.
What is the real difference? I have read everything from gas impulse and pressure curves to cyclic rate, etc. Seems like a lot about nothing to me as I used a lopro gas block under a 12" LaRue rail.. |
| The short story. Timing and pressure come to mind immediately. A carbine starts unlocking sooner than a rifle. Chamber pressure is higher causing the case to stick to chamber more than at the same point in the unlock/extract cycle for a rifle. Port pressure is about double that of a rifle don’t quote me, but I think about 26k PSI. vs 13k PSI. Lesser quality weapons do not stand up to this well in heavy use. |
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I don't remember anyone saying that a carbine gas system can't work. Midlength is better for a 16" barrel and there are many benefits in reliability/mechanically and in human factors. I havent had any issues so far. I didnt use any cheap parts , everything is quality stuff. LMT BCG, BCM flat top upper, etc. All that is left is to pick an optic. I have YHM BUIS's but I am torn between an Aimpoint of some form or an ACOG.. |
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So what is better for a 14.5 inch barrel?... a carbine or mid length gas system? 14.5" is optimized for a carbine gas system. I have 2 carbines, both Colt, one in 16" and one in 14.5". The 14.5" shoots "nicer" than the 16". I also have a 14.5" midlength which as stated above has reduced felt recoil and a longer sight radius. I prefer the midlength over the carbine when comparing 14.5" barrels. |
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So what is better for a 14.5 inch barrel?... a carbine or mid length gas system? 14.5" is optimized for a carbine gas system. I have 2 carbines, both Colt, one in 16" and one in 14.5". The 14.5" shoots "nicer" than the 16". I also have a 14.5" midlength which as stated above has reduced felt recoil and a longer sight radius. I prefer the midlength over the carbine when comparing 14.5" barrels. As for sight radius, I have my front sight at the very end of the rail. I am not certain but it is as long or longer than a standard 20" A2 radius. |
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So what is better for a 14.5 inch barrel?... a carbine or mid length gas system? 14.5" is optimized for a carbine gas system. I have 2 carbines, both Colt, one in 16" and one in 14.5". The 14.5" shoots "nicer" than the 16". I also have a 14.5" midlength which as stated above has reduced felt recoil and a longer sight radius. I prefer the midlength over the carbine when comparing 14.5" barrels. As for sight radius, I have my front sight at the very end of the rail. I am not certain but it is as long or longer than a standard 20" A2 radius. If your running a Larue 12" and have the sight mounted at the end of the rail then your just short of 20" rifle length sight radius ... because the A2 sight would be mounted in front of that rail on a rifle. |
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So what is better for a 14.5 inch barrel?... a carbine or mid length gas system? 14.5" is optimized for a carbine gas system. I have 2 carbines, both Colt, one in 16" and one in 14.5". The 14.5" shoots "nicer" than the 16". I also have a 14.5" midlength which as stated above has reduced felt recoil and a longer sight radius. I prefer the midlength over the carbine when comparing 14.5" barrels. As for sight radius, I have my front sight at the very end of the rail. I am not certain but it is as long or longer than a standard 20" A2 radius. If your running a Larue 12" and have the sight mounted at the end of the rail then your just short of 20" rifle length sight radius ... because the A2 sight would be mounted in front of that rail on a rifle. Your right, I thought of that just as I hit submit but Its still plenty long.. |
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http://www.03designgroup.com/technotes/carbine-vs-mid-length-gas-system
When talking about the different gas systems on a 16" barrel, think about the distance from the gas hole to the end of the barrel. The longer that the bullet is in the barrel after the bullet passes the gas hole, the more gas that is getting pushed back through the gas tube and back into the gas key. The end result is a sharper recoil impulse. This is why on a 16" barrel, a mid-length gas system is slightly smoother than a carbine length gas system. The distance from the gas hole to the end of the A2 flash hider on a 16" barrel with carbine-length gas system is approximatley 9.5". The distance from the gas hole to the end of the A2 flash hider on a 20" barrel with rifle length gas system is approximatley 7.5" The distance from the gas hole to the end of the A2 flash hider on a 16" barrel with mid-length gas system is approximatley 7.5" The distance from the gas hole to the end of the A2 flash hider on a 14.5" barrel with carbine-length gas system is approximatley 7.5" |
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aNyone? I wouldn't recommend it. Wondering why you would want a shorter gas system length on a longer barrel than what it's intended for. The shorter you go with gas systems and/or barrels the more critical everything becomes. High gas pressures and very short times make everything very touchy. |
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I use to have the magnum resarch lone eagle 223 pistol w 12" barrel and i know I didn't like the recoil from it so I probablly willn't like Any Ar shorter whats you guys opinion on ar short barrel recoil? Felt recoil on a pistol is not comparable to felt recoil on a rifle. AR's don't exactly have "recoil". <- (arguable point) So to me there isn't "recoil" in a SBR AR. My 9mm AR's have more recoil than any 5.56 AR I own or have ever shot. |
| Most of what you perceive as recoil in an AR is the B/BC/Buffer stack hitting the back of the buffer tube to end its rearward travel. That impact is much more noticable in over-powered/overgassed ARs as the total energy into the operating system and therefore the velocity of the reciprocating parts increases substantially. Solution is to reduce the amount of energy going into the operating system by lowering the gas pressure or volume. In competition rifles for 3-gun or other action shooting disciplines it's common to use longer-than normal gas systems frequently in combination with a gas adjustment so as to run the absolute minimum amount of gas that will function the rifle in order to lessen that perceived recoil. |
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