View Full Version : carbine vs midlength
http://www.03designgroup.com/technotes/carbine-vs-mid-length-gas-system
After reading I am now scratching my head, what is the point of a 14.5 mid length? besides all the cool kids having them?
SnackCracker
04-06-10, 18:13
The mid=length is less harsh on the action, resulting in smoother extraction similar to the rifle gas system. The middy naturally gives the shooter a longer sight radius than the carbine, but not as long as the rifle. It's an excellent compromise if you are going to run a 16" barrel. Mid Length has a "softer" recoil and is easier on the gun.
Many people feel that Carbines tend to be "over gassed" which is why the run heavier buffers.
12" is 60% of 20"
9.5" is 65% of 14.5"
7.5" is 51% of 14.5"
it's still not perfect, but it's closer to the optimum ratio of build/dwell
its about building a proper ratio, not adhering to a specific length.
12" is 60% of 20"
9.5" is 65% of 14.5"
7.5" is 51% of 14.5"
it's still not perfect, but it's closer to the optimum ratio of build/dwell
its about building a proper ratio, not adhering to a specific length.
the midlengthe was really designed for a 16" barrel right?
seems it could be slightly undergassed with a 14.5"
I don't know what that website says... but if you ever study any of the computer programs (like QuickLoad) that chart the burn rates and pressure levels of small arms loads you'll see just how valuable moving the gas port farther down the barrel from the carbine location.
I'd be all over the 14.5 middy if I wasn't so long on AR uppers already.
the midlengthe was really designed for a 16" barrel right?
seems it could be slightly undergassed with a 14.5"
keep in kind gas length is only part of the equation. ammo pressure, buffer weight, port size, etc... all factor in too.
in the end, you can do whatever you can get away with, with this platform. and people are definitely getting away with mid-length 14.5s, and they seem to shoot really well.
There are two middies at our house . mine is a 16 inch and my wife's is a 14.5 . Both run various brass case ammo ( both 5.56 & .223 ) with H buffers , but the 14.5 needs the carbine buffer to run Wolf 55 gn . The 16 inch does ok with the H buffer & Wolf 55 grn.
Mine runs fine so far, carbine buffer. BCM specifically says this 14.5 middy was designed with an H buffer to be a sweet, soft and fast shooter with quality milspec 5.56 pressure ammo, and if shooting anything else switch to carbine buffer. So gbear48 is spot on. I may just leave the carbine buffer in it as I like my rifles to digest anything I feed them at any time. No junk ammo, but I happen to like the .223 64gr SP loads as well as 69gr match. Figure it's no worse for wear given that it IS a middy and a 14.5 to boot, shortening dwell time.
I had always liked 14.5's but wouldn't buy one because of the perm FH. I was also a long time middie fan. When I bought my 16.0 sabre middie I figured this would be a keeper so took the plunge, a couple years ago and had it chopped. I was taking a chance with the port and everything else balancing out. After a couple of years and probably 4000 rounds it's probably my favorite carbine. This was also one of my first complete builds from scratch. It has sycronicity, it runs great. I use a carbine buffer and always have on this one. I liked the middies so much I sold the original DD carbine barrel on my DD rifle and put a middie on it. I still have 2 carbine length systems, one on a 14.5 pencil barrel and one on my SBR but for most applications I prefer the middie. I don't know if it's any better but I do know they are not any less reliable.
I have been running a 14.5" Noveske Afghan Mid Length for about 3 years now and it runs like a champ. It is more comfortable to shot than my Colt carbine. I am a huge fan of the 14.5 Mid barrels.
keep in kind gas length is only part of the equation. ammo pressure, buffer weight, port size, etc... all factor in too.
in the end, you can do whatever you can get away with, with this platform. and people are definitely getting away with mid-length 14.5s, and they seem to shoot really well.
So did BCM compensate the gas port size for the reduction in length to the end of the barrel? just wondering after reading usmc's info about length to the end of the barrel.
So did BCM compensate the gas port size for the reduction in length to the end of the barrel? just wondering after reading usmc's info about length to the end of the barrel.
I wouldn't guess there'd be any port mods necessary. There was a guy here who reported that LMT had cut down 14.5" carbine barrels to 12.5 with NO port mods. And the guns ran great.
I just hate how they add the 1.5" welded part on the end to make it a 16" :(
So did BCM compensate the gas port size for the reduction in length to the end of the barrel? just wondering after reading usmc's info about length to the end of the barrel.
since the 14.5s with .062 ports and carbine gas are over-gassed, i would imagine that extending the port out is enough without enlarging. i just pointed out the other variables that go into chasing a perfect balance. aside from Grant's "perfect SBR," i haven't ever seen any attempts to get really, truly "perfect" about it, though. generally people stop once the achieve "it works!"
I just hate how they add the 1.5" welded part on the end to make it a 16" :(
SBR and you dont have to
FMJs-of-Freedom
04-07-10, 20:42
I am saving up for a 14.5 middy pencil build. FMJs-of-Freedom
SBR and you dont have to
So according to the stats above if doing an SBR people would rather a 14.5" than say a stubby 10"?
So according to the stats above if doing an SBR people would rather a 14.5" than say a stubby 10"?
If you are going to SBR then you would probably want to go shorter. Perm attaching a muzzle decive is not as big a deal as most people make it out to be. The MD guys have been running BCM 14.5" middys and have yet to have any problems with them.
If you are going to SBR then you would probably want to go shorter. Perm attaching a muzzle decive is not as big a deal as most people make it out to be. The MD guys have been running BCM 14.5" middys and have yet to have any problems with them.
I was not saying it because its a big deal, but if your going to have a 14.5" bbl why not put it to use, instead of having an overall length of 16"? For example I'd never have a 10" bbl w/ a 6" welded end on it. That would defeat the purpose of having s short bbl, no? That being said if I'm going to pay for an SBR then I'm going to get my moneys worth with a 10" haha. Although I'm still new to this stuff, just my way of thinking. :D
I was not saying it because its a big deal, but if your going to have a 14.5" bbl why not put it to use, instead of having an overall length of 16"? For example I'd never have a 10" bbl w/ a 6" welded end on it. That would defeat the purpose of having s short bbl, no? That being said if I'm going to pay for an SBR then I'm going to get my moneys worth with a 10" haha. Although I'm still new to this stuff, just my way of thinking. :D
by putting the shortest of short muzzle devices on the 14.5, you're still bringing the overall length out to almost 16". so no matter how you shake it, you're going to be right around 16 in the end, and thats why people say "if you're gonna SBR, might as well go shorter."
but since anything below 16 is SBR, and since the question is in regards to 14.5 barrels, i don't see what difference it makes.. SBR is SBR.
I was not saying it because its a big deal, but if your going to have a 14.5" bbl why not put it to use, instead of having an overall length of 16"? For example I'd never have a 10" bbl w/ a 6" welded end on it. That would defeat the purpose of having s short bbl, no? That being said if I'm going to pay for an SBR then I'm going to get my moneys worth with a 10" haha. Although I'm still new to this stuff, just my way of thinking. :D
That's a bit extreme. It's like saying, "I am going to get a 7" barrel and weld a 9" flash hider." There are muzzle devices that will get your barrel to 16" and still have it be aesthetically pleasing. Welding a 6" muzzle device on a 10" barrel just makes it look wrong.
Er...
Are we forgetting that 16 inch barrels are 16 inches plus the length of the flash hider?
A 14.5 inch barrel is SHORTER than a civi legal 16 inch barreled gun.
For people that DONT want to spend the money on a tax stamp permanently affixing a FH is no big deal.
I dont know about you but i dont routinely change my flash hiders.
That's a bit extreme. It's like saying, "I am going to get a 7" barrel and weld a 9" flash hider." There are muzzle devices that will get your barrel to 16" and still have it be aesthetically pleasing. Welding a 6" muzzle device on a 10" barrel just makes it look wrong.
To embrace the absurdity we used to joke about getting a 1" barrel and welding a 15" flash hider on it over on ARF. :p
polymorpheous
04-11-10, 10:17
i have one of those fancy hammer forged barrels from DD. had a extended A2 flash hider permed. honestly, the extended flash hider is only about 1/4" longer than the standard.
SBR a 14.5" doesn't seem worth it to me.
i'm saving that for a 11.5"!;)
I don't understand why these 14.5" vs. 16" discussions always turn this way.
Their are pros and cons to each argument and as long as the owner is aware of these pros and cons it's really up to them and not really anyone else. I've certainly made the argument both ways in the past but I now think it's better to make sure that the buyer understands that they are getting themselves into and move on.
It's important to remember also that the upper is not the serial-numbered part here. Absolute worst case (ban-state resident that totally changes their mind) they can recover at least part of the cost of the original upper by selling it off and starting from scratch. At most we're talking about a $200 loss when we're dealing with a likely $2k+/- overall firearm (and the total is only going to be still more if you ARE in a ban state).
Here are some actual facts that I posted in the other port position thread if any one is interested.
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.
14.5 vs 16
This argument has actually always been 16 vs 17.5 in my mind. Yes, I could put an A2 on the end of a 16in barrel which will make it near the same OAL as a 3in muzzle device pinned on a 14.5in barrel, and then use this to make my argument that 14.5s are dumb. But this is not what we are talking about. What I really want is a PWS FSC556 on the end of whatever length barrel I choose, and I also want the shortest barrel assembly OAL possible with the least amount of hassle. This is where the 14.5 shines.
1. The fsc556 pinned on a 14.5 brings the OAL to 16inches. The fsc556 on a 16 brings the OAL to 17.5inches.
2. The $40 and inconvenience involved in pinning a muzzle device does not nearly rival the $200 and inconvenience of applying for, waiting for, and traveling with an SBR.
3. To me, there are noticeable differences in handling a 14.5 vs a 16, so the slight inconvenience of having a muzzle device "perm" attached is worth it for the 1.5inches saved.
Middy vs Carbine
I have not had the opportunity to shoot enough of both at the same time to really notice a difference, but those who have say that the middy is not as harsh of a gas system, as already mentioned. Plus the longer sight radius if you plan to use your irons a lot. What is worth it to me though is the extra rail space. If you are going to have an FSB (that's another argument for another thread) then the middy gives you 2 more inches of rail space (referring to standard rails, and that's another argument for another thread too).
Conclusion
So, to me at least, it seems like BCMs middy 14.5 is a pretty sweet setup with the best of both worlds, if the previously mentioned characteristics are something you desire.
Now, having said all that, here is my 14.5 carbine gas setup. :D
http://i415.photobucket.com/albums/pp238/ravenwulfe101/DSCN4194.jpg?t=1273435427
Jay Cunningham
05-09-10, 15:13
In my own experience, most of the individuals who obsess over carbine vs. mid-length gas systems would be better off doing some position shooting with their iron sights.
since the 14.5s with .062 ports and carbine gas are over-gassed, i would imagine that extending the port out is enough without enlarging. i just pointed out the other variables that go into chasing a perfect balance. aside from Grant's "perfect SBR," i haven't ever seen any attempts to get really, truly "perfect" about it, though. generally people stop once the achieve "it works!"
How do you define over-gassed? By cyclic rate or bolt carrier velocity? Which buffer?
In my own experience, most of the individuals who obsess over carbine vs. mid-length gas systems would be better off doing some position shooting with their iron sights.
They likely don't even have irons sights. :rolleyes: And if they do, they're probably flip up crap that isn't BZO'd for shit anyway.
Exactly how many middy vs carbine threads do we need?
Exactly how many middy vs carbine threads do we need?
well this one was for all intents and purposes, dead, until a specific question was asked about a statement made defining "overgassed".
I think it's a valid question, regardless of the thread title it happens to fall under and should be discussed.
IMO, much more valuable than simply doing a drive-by post saying people who obsess about length are silly and should wear little pink skirts or some such...
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