I see 14.5s with midlength.
I see 16s with rifle length.
I have a feeling as to why this trend is happening, but would love to hear the official reason, from someone officially knowledgeable.
Thanks
i don’t know what “officially knowledgeable” means, but i know plenty.
it’s happening because it causes a softer cycle… and this information isn’t self-evident, but is as close to it as you can get. maybe i’m missing something in your post?
Maybe I should put it a different way.
We are pushing the ports out, but the military is not…WTF?
not gonna happen… doesn’t need to. the M4 works… 7.5" on a 14.5" barrel isn’t perfect, but neither is 9.5". better to be over gassed than under gassed.
not to mention it’d be horribly expensive, take tens of thousands of man-hours… on a system that’ll likely be phased out before they could finish.
That is the part that makes me ask the question in the technical section.
By pushing out the gas port are we adding issues to a rifle that should work.
have you seen this recent thread? http://m4carbine.net/showthread.php?t=51187
might help put it into perspective… or might not.
it’s just about end-user demand and preference. people want to sacrifice a little gas to achieve softer recoil- so manufacturers responded with products that meet the demand. since neither system, carb nor mid, actually achieves a perfect balance, the civilian user is left to chose for himself based on his priorities.
the military needs the system that’s going to work the best (out of the existing options) under the worst conditions- and that’s going to be carbine gas. the individual private citizen doesn’t need this extreme requirement, so he can opt for the mid.
I missed that thread.
At least I know I am asking the right questions as I try to decide if I want a 14.5 with carbine gas or midlength gas.
I want something that is going to run 100% of the time. It looks like I can get that with 14.5 mid length and carbine buffer OR 14.5 with carbine buffer and H2 buffer. Decisions, decisions.
Ideal.
I see 16s with rifle length.
Less than optimal, and usually done by guys with 20" barrels who want to cut them down. Can be made to function well, but mid length gas is more ideal.
I have a feeling as to why this trend is happening, but would love to hear the official reason, from someone officially knowledgeable.
If you look at a line chart of the pressure of the burning propellant, you’ll see that moving the gas port from the 7.5" point of the carbine down to the mid length position you reduce the PSI from (in one hand load example) 25,000 psi to about 19,000 psi.
Not a bad improvement. If you move out to rifle length gas port, you’re at about 15,000 psi.
These examples are from a hand load with a peak pressure of only 40,000 psi.
Maybe I should put it a different way.
We are pushing the ports out, but the military is not…WTF?
Doesn’t the FSB on the military 14.5" need to stay where it is in order to mount the M203? I don’t know (I’m a civilian and have obviously never used one), but I am under the impression that an unmodified M203 would not mount up to a 14.5" barrel with a midlength gas system.
The other reason the military isn’t pushing their gas ports out is that they don’t use 16" barrels on M4’s; they use 14.5’s, which have a shorter dwell time.
Doesn’t the FSB on the military 14.5" need to stay where it is in order to mount the M203? I don’t know (I’m a civilian and have obviously never used one), but I am under the impression that an unmodified M203 would not mount up to a 14.5" barrel with a midlength gas system.
The M203 doesn’t mount anywhere on the FSB, it mounts as the bottom part of the handguard.
Moving the FSB would screw up bayonet mounting, however.
Longer gas systems shoot softer, this results also in less wear on parts, cleaner running gun, slightly less heat generated, and less violent recoil.
For midlength their really isn’t a set standard. There are two lengths of midlength ArmaLites length and what RRA and everyone else uses. Just because there are new trends in the black rifle industry doesn’t mean the US Military will suddenly change to the new trend.
For my purposes 14.5" is the shortest possible barrel with a midlength if you want it reliable. Sure there are people with 13.5s" with midlengths that work…study group of 1 - few.
For my purposes 18" is the shortest barrel for rifle length gas systems. Sure there are people with 16-17" barrels with rifle gas systems and huge gas ports that work in warm/hot weather…study group of a few.
The question is, IS this a trend or is it really better?
I am only interested in the 14.5.
its both and neither… it’s just another option.
The question is, IS this a trend or is it really better?
It really IS better, but not enough for the military to switch.
IMHO yes a midlength is better than a CAR length gas system on a 14.5-16" barrel. It’s not too shabby on a 18" barrel but an intermediate gas length on a 18" is better. Rifle gas length on a 18" is pretty soft too.
There are still versions of the M203 that mount on the barrel.
An M203 will NOT mount to a mid length.
Dustin