newbuckeye
Member
I am thinking of getting an 11.5 inch upper, and am wondering how it will affect the range/accuracy compared to the 16 and 20". It's a 1-9 like the others, just shorter.
M-4 barrel length
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rcmodel
Member in memoriam
I will not affect the accuracy.
It will affect the velocity, to the tune of about 500 FPS less then a 20"
Or 400 FPS less then a 16".
That of course affects the flatter trajectory & higher energy of the longer barrels at long range.
And you probably know, but a rifle barrel has to be 16" long to prevent it being classified as a SBR and need a $200 ATF tax stamp.
You can permanently attach a long flash hider to the shorter barrel by welding or a blind pin that cannot be removed to make it 16".
Myself?
I'd rather have the velocity increase of the longer barrel to start with.
Velocity is what makes the .223 work.
rc
It will affect the velocity, to the tune of about 500 FPS less then a 20"
Or 400 FPS less then a 16".
That of course affects the flatter trajectory & higher energy of the longer barrels at long range.
And you probably know, but a rifle barrel has to be 16" long to prevent it being classified as a SBR and need a $200 ATF tax stamp.
You can permanently attach a long flash hider to the shorter barrel by welding or a blind pin that cannot be removed to make it 16".
Myself?
I'd rather have the velocity increase of the longer barrel to start with.
Velocity is what makes the .223 work.
rc
Theohazard
Member
1911 guy
Member
I agree with rcmodel. While the short ones look cool, they give up a lot of velocity, they require a 200 dollar tax stamp with an approximate six month wait and they often have function problems due to the extremely short dwell time. The fixes to correct these cost more money.
XM177
XM177E1 (With forward assist)
Colt Commando carbine
These are the 11.5" barrel weapons
A SOCOM CDW (Close Defense Weapon) uses a 10.5" barrel.
All M4 Carbines use 14.5" 1/7" twist barrels
Having had an 11.5" Carbine and now owning a 14.5" M4 1/7" with permanent flash suppressor, (YHM Phantom, pinned and welded),
my suggestion is go with a 14.5" upper.
Less blast, more velocity, lots more practical accuracy.
XM177E1 (With forward assist)
Colt Commando carbine
These are the 11.5" barrel weapons
A SOCOM CDW (Close Defense Weapon) uses a 10.5" barrel.
All M4 Carbines use 14.5" 1/7" twist barrels
Having had an 11.5" Carbine and now owning a 14.5" M4 1/7" with permanent flash suppressor, (YHM Phantom, pinned and welded),
my suggestion is go with a 14.5" upper.
Less blast, more velocity, lots more practical accuracy.
henschman
Member
Instead of the tax stamp, you could put a pistol buffer and SB-15 "arm brace" on it. It works just like a stock, but keeps the gun legally a pistol.
Arizona_Mike
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A few months ago some folks on this and other forms were freaking out about about me using an SB15 while waiting for a stamp. Last night at USA Auto Weapons in Scottsdale I saw a whole rack of these "pistols" for sale to the general public. SIG is even selling them with an oversized pistol buffer tube to increase "length of pull" er . . . I mean arm length 
The SB15 appears to be becoming common. Large companies are selling their "NFA hacks" as eagerly as small companies were in the last few years.
Mike
The SB15 appears to be becoming common. Large companies are selling their "NFA hacks" as eagerly as small companies were in the last few years.
Mike
Theohazard
Member
Yeah, the SB15 is somewhat revolutionary when it comes to the whole AR pistol vs. SBR conundrum. And before someone comes on here and says it's illegal to shoot from the shoulder (it seems to happen any time the SB15 is mentioned on the internet): No, it's perfectly legal to shoulder it and shoot it like a rifle. The BATFE cannot restrict how you shoot a firearm, only how that firearm is designed. And they've officially determined that the SB15 is an arm brace that doesn't change a firearm's designation as a pistol. Think about it: A pistol is defined by the BATFE as being designed to be fired with one hand only; if it was illegal to shoulder the SB15 then it would also be illegal to shoot any handgun with a two-handed grip.
FrankCastleThePunisher
Member
The Sig M400 AR pistol comes comes with a 11.5" barrel and 1x7 twist rate and the SB15 brace for about 28" OAL, and without having to buy the stamp.
11.5" upper: Yes
1/9 twist: No, unless you want to be limited to shorter length bullets like the 55 grainers normally are. Because of the velocity loss from a barrel this short, RPMs will be lower making longer bullets less stable or even unstable
An 11.5 inch rifle is very handy and will make hits out to 300 yards easily. It's also a good length if you want to suppress it. The better makers like BCM put out very reliable rifles in this length. If I had the money, I'd be rockin' a suppressed 10.5 carbine. SBRs are a blast to shoot (pun intended)
DoubleTapDrew
Member
I dunno that looks pretty cool but the BATFE also OK'ed the akins accelerator before they changed their mind and left a lot of folks with $1,000 non functioning 10/22 stocks
MachIVshooter
Member
12-15 right now, actually
Not if they're done right. My 7.5 and 12.5 are every bit as reliable as my 16 inchers.
Arizona_Mike
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If you are worried about the wait time either:
1. Get a trust, sign up for e-forms, and get your e-form approved in about 90-95 days.
2. Build it as a pistol with a virgin receiver and a SB-15 while waiting for a paper Form 1.
My 10.5" 300BLK with pistol gas and an H2 buffer is also 100% reliable. In fact it would be a little overgassed if it were not for the Syrac.
Mike
wally
Member
Another thing that always seems to come up in these "loophole" threads, but overlooks that the Akins Accelerator as approved was *not* the same as what they ended up delivering -- the added spring negated the approval and changed the classification.
Theohazard
Member
Like Wally said, the Akins is different. And -- more importantly -- the SB15 is fairly cut-and-dried: THE BATFE has said it's designed as an arm brace for one-handed use. The only way they could justify changing their minds and banning it is if they determined that SIG was actually designing it to get around the SBR laws. But SIG is doing a great job of holding to the official "arm brace" line; there's zero evidence that it's intended to let you get around the SBR laws, even though we all know it is.DoubleTapDrew said:
Sure, I guess the BATFE could ban the SB15. But as long as they haven't banned much more scary things like the Slide-Fire stock, I highly doubt they'll worry too much about a rubber arm brace that just happens to work as a stock.
newbuckeye
Member
Thanks everybody! I am going to build a pistol lower for it, but I am also going to look for the 1/7. That wont be a deal breaker for me tho because most of what I shoot is already 55gr. I have some heavier stuff I use for yotes and such but not that much.
meanmrmustard
Member
I agree with Mistwolf that SBRs/pistols of a working length (10.5"+) are not only handy, but fun.
For those who say that the 5.56 needs that speed of a longer tube for effectiveness via velocity, I ask you this:
Have you seen the ballistic gel impact footage/pics of the Mk 262 Mod 1 from an 11.5 barrel? That round in media with a MV of only 2300 fps looks like a grenade went off at the ten inch mark.
Devastating.
For those who say that the 5.56 needs that speed of a longer tube for effectiveness via velocity, I ask you this:
Have you seen the ballistic gel impact footage/pics of the Mk 262 Mod 1 from an 11.5 barrel? That round in media with a MV of only 2300 fps looks like a grenade went off at the ten inch mark.
Devastating.
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