Short Barrel Uppers

[bigcoastie]

So I've gotten to the point where I have two 16" uppers and I started to look at SPR type uppers and shorty uppers.

I don't shoot over 300 yards all that much and I know if I get an SPR it's going to be a spend fest because I'll put a stupid expensive optic on it. That being said I'm in the military and don't want to deal with the pain in the ass of moving to a state that doesn't allow sbrs so it will be an AR pistol for the time being and eventually an SBR.

What do you think of 7.5" uppers compared to 10.5" uppers in terms of reliability only not accuracy or velocity. I'm actually looking at Raniers 7.5 http://www.rainierarms.com/?page=sho...roduct_id=1095 and their http://www.rainierarms.com/?page=sho...roduct_id=1361

[Stickman]

So I've gotten to the point where I have two 16" uppers and I started to look at SPR type uppers and shorty uppers.

I don't shoot over 300 yards all that much and I know if I get an SPR it's going to be a spend fest because I'll put a stupid expensive optic on it. That being said I'm in the military and don't want to deal with the pain in the ass of moving to a state that doesn't allow sbrs so it will be an AR pistol for the time being and eventually an SBR.

What do you think of 7.5" uppers compared to 10.5" uppers in terms of reliability only not accuracy or velocity. I'm actually looking at Raniers 7.5 http://www.rainierarms.com/?page=sho...roduct_id=1095 and their http://www.rainierarms.com/?page=sho...roduct_id=1361

I would go with a 10.5", 11.5", or 12.5" for a SBR. The pickup in FPS is just too large of a difference when we bring fragmentation into the discussion.

If you are talking about just popping paper as a fun-gun, the shorter barrels are certainly enjoyable, I've got a 9.5" barreled upper thats everyone loves to shoot with.

[Keebsley]

It all depends on your use. A good friend of mine has an AR pistol for vehicle use. Nice for getting to in a tight and confined area. Will it fragment reliably? Probably not. But for it's intended use, it fills its role. I had the debate whether to go 7.5" or 10.5" and I went with 10.5" and I don't regret it. As it has been preached before: The Mission drives the equipment.

[rob_s]

Strictly in terms of reliability as you asked, the 7.5s are a pain in the ass. I've long since gotten over the "fun" of tinkering with a gun to make it run and prefer to have guns that shoot reliably and do so from the get go, with whatever additional tinkering I do being on a voluntary basis. If you have the time, like a challenge, or are just lucky the 7.5 may be feasible for you.

[Army Chief]

I had started to go down much the path that Stick did, before I was called away from this post. Put simply, if you're after entertainment value, a sub-10" can likely meet your objectives. It isn't terribly practical, but neither is a belt-fed HK-21k -- I'd still like to own one. There is a place for these kinds of flamethrowers, but as a practical matter, it isn't as a serious defensive arm.

Ken Elmore knows this weapon system about as well as anyone, and he told me once upon a time that 10" is really about the shortest "working gun" configuration that makes any kind of sense. Depending upon who you listen to, 11.5" is really optimal in a minimalist configuration. 12.5" is another excellent compromise, if you don't mind the extra inch.

For the moment (while I'm on active duty), non-NFA 14.5" configurations are about the most sensible for me, and I suspect you're in a similar situation, since you never know where your next PCS will take you. That said, if/when you decide to wade into NFA waters, I would do it with a 10.5" or 11.5" configuration. Either is compact enough to justify the added expense and red tape, but still long enough to deliver satisfactory terminal ballistics.

AC

[Cameron]

I have a couple of 16" ARs and decided to get an SBR and thought that with the Tax Stamp requirements it makes sense to go with the shortest length that is reliable. So I bought a 10.5" LMT upper. It has been 100% reliable with all ammo type, with all buffer weights, and even suppressed.

I don't really buy into the fragmentation threshold arguement. It is obvious that the SBR is a rifle setup for short ranges and it certainly will perform well within the parameters it was designed for.

[Stickman]

I don't really buy into the fragmentation threshold arguement. It is obvious that the SBR is a rifle setup for short ranges and it certainly will perform well within the parameters it was designed for.

Another good argument against fragmentation threshold is that most of us are under no obligation to use FMJ ammo. There is plenty of SP ammo around for people who are looking to go that route.

There is a chart floating around somewhere which lists the velocity of a few different variants of 5.56 ammunition out of most different barrel lengths. I wish I would have bookmarked the link.

[rob_s]

That is true, but all ammo does have a minimum velocity at which it performs as designed. This does NOT mean that I want to get shot with a 5.56 out of a 7.5" barrel, it just means that your ammo of choice may not perform as designed or desired.

If you expect to use a 7.5" barrel for defensive purposes (whether professionally or privately) I would strongly suggest making sure of the velocity floor of the round of choice and doing chrono testing to determine if the barrel reaches that floor and then out to what distance it continues to exceed that floor.

As a range toy, who cares. And that's really the realm of the 7.5" AR anyway.

[bigcoastie]

Well ya'll have talked me into a 10.5" I guess my biggest question is as a range toy only and using a pistol lower is it going to kill me to shoot 50-100 rounds in a day. I've tried to find info about "shouldering" the buffer tube but most people are putting them up to their cheeks or just holding them out in front of them.

Here's a velocity chart I found for various barrel lengths as well.

MK 262 VELOCITY DATA
__________________________________


7.5" 2053 FPS ... 10.5" 2363 FPS
DIFFERENCE 310 FPS
DIFFERENCE/INCH 103 FPS

10.5" 2363 FPS ... 14.5" 2576 FPS
DIFFERENCE 213 FPS
DIFFERENCE/INCH 53 FPS

14.5" 2576 FPS ... 16" 2669 FPS
DIFFERENCE 93 FPS
DIFFERENCE/INCH 62 FPS

16" 2669 FPS ... 18" 2769 FPS
DIFFERENCE 100 FPS
DIFFERENCE/INCH 50 FPS

18" 2769 FPS ... 20" 2818 FPS
DIFFERENCE 49 FPS
DIFFERENCE/INCH 25 FPS



M855 VELOCITY DATA
__________________________

7.5" 2244 FPS ... 10.5" 2639 FPS
DIFFERENCE 395 FPS
DIFFERENCE/INCH 132 FPS

10.5" 2639 FPS ... 14.5" 2861 FPS
DIFFERENCE 222 FPS
DIFFERENCE/INCH 56 FPS

14.5" 2861 FPS ... 16" 2938 FPS
DIFFERENCE 77 FPS
DIFFERENCE/INCH 51 FPS

16" 2938 FPS ... 18" 3046 FPS
DIFFERENCE 108 FPS
DIFFERENCE/INCH 54 FPS

18" 3046 FPS ... 20" 3061 FPS
DIFFERENCE 15 FPS
DIFFERENCE/INCH 7.5 FPS


XM193 VELOCITY DATA
_________________________________


7.5" 2364 FPS ... 10.5" 2755 FPS
DIFFERENCE 391 FPS
DIFFERENCE/INCH 130 FPS PER INCH

10.5" 2755 FPS ... 14.5" 2984 FPS
DIFFERENCE 229 FPS
DIFFERENCE/INCH 57 FPS PER INCH

14.5" 2984 FPS ... 16" 3075 FPS
DIFFERENCE 91 FPS
DIFFERENCE/INCH 61 FPS

16" 3075 FPS ... 18" 3245 FPS
DIFFERENCE 170 FPS
DIFFERENCE/INCH 85 FPS

18" 3245 ... 20" 3254 FPS
DIFFERENCE 9 FPS
DIFFERENCE/INCH 4.5 FPS

[Stickman]

Coastie,



Remember how the SAS used to shoot the MP5s while wearing masks? Use the sling, push out, and get stable.... with a little practice its very doable. Since you are not looking to use it for boarding, its something to play around with and see how you like it.

[Rated21R]

11.5 vs. 12.5 are both good to go? For a general use, HD, carbine class, which would you prefer? Thanks.

[Stickman]

I would personally go with the 12.5" barrel, no question about it.

[rob_s]

whether I'd choose 10.5", 11.5", or 12.5" for an SBR would depend on a lot of factors like intended use as well as can or no can, and if can then which one.

For example, the AAC SPR/M4 won't work with a barrel under 12.5" (although there's some suggestion that it might work with an 11.5" barrel and a cut-down gas block), an Ops can needs the 11.5" barrel minimum, etc.

[Army Chief]

True enough. In my own mind, 10.5" is a solid choice if you ultimately intend to supress the carbine, since it delivers acceptable ballistics and still allows for a reasonable overal length with a can installed.

On the other hand, if you know that you cannot, or simply will not, be looking to supress the carbine at some point, then 11.5" or 12.5" makes a lot more sense -- with my personal preference running toward the latter. There is an improvement in terminal ballistics, of course, but the added length also attenuates blast better and smooths out the recoil pulse a bit. You may or may not feel that at your shoulder, but it is easier on the internals of your gun.

Even 14.5" is still a fairly handy configuration, but this puts you in the No Man's Land of NFA law, in that you have to decide if it is worth the extra work, waiting and expense to have a removable flash supressor, when a permanent installation would achieve much the same thing. I would argue that it is, but there are enough non-NFA 14.5" carbines out there to cause many to wonder "what's the point?" for an inch-and-a-half reduction from the 16" OAL legal Title I minimum.

AC