AR question

[USAF_Vet]

I'm building an AR pistol (Aero Precision stripper lower, Magpul pistol grip, PSA LPK) and have a quick question about the buffer, tube and spring kit.

I got a steal of a deal on a carbine length tube, buffer and spring, no stock but it can accept one. I'm going to mill off the catch rail for the collapsible stock, but my question isn't a legal one of whether or not it's an issue if a pistol can accept a stock. My question is how well will the carbine length tube with carbine spring and buffer cycle with a short upper. I haven't decided on a upper just yet, still going back and forth over 7.5" and 10.5" barrels. I know the 10.5 is the better choice ballistically, but the 7.5 match grade I'm looking at just looks so nice.

Anyway, will I need to swap to a pistol weight buffer and pistol length spring for proper cycling, or will my carbine kit work ok?

 

[Ibmikey]

I would spend a few bucks on a proper pistol tube (receiver extension) with provisions for a Sig brace if wanted one in the future. The standard carbine spring and buffer are used however I have found aa H2 buffer works best in my pistol, just depends on gas flow. My latest pistol in 300 Blackout uses a MidWest Ind. buffer tube and Sig brace, shot several hundred rounds yesterday. It is death on soda cans and dirt clods.

 

[Fishbed77]

Get yourself a KAK Super SIG buffer tube and an SB-15 and be done with it. Not sure about the 7.5" barrel, but an H2 buffer and carbine spring will work just right with a 10.5" barrel.

 

[Warp]

I'm building an AR pistol (Aero Precision stripper lower, Magpul pistol grip, PSA LPK) and have a quick question about the buffer, tube and spring kit.

I got a steal of a deal on a carbine length tube, buffer and spring, no stock but it can accept one. I'm going to mill off the catch rail for the collapsible stock, but my question isn't a legal one of whether or not it's an issue if a pistol can accept a stock. My question is how well will the carbine length tube with carbine spring and buffer cycle with a short upper. I haven't decided on a upper just yet, still going back and forth over 7.5" and 10.5" barrels. I know the 10.5 is the better choice ballistically, but the 7.5 match grade I'm looking at just looks so nice.

Anyway, will I need to swap to a pistol weight buffer and pistol length spring for proper cycling, or will my carbine kit work ok?

I suggest not even considering a 7.5" barrel unless this is a pure 100% toy for making fireballs and nothing else.

 

[Ryanxia]

I kept the carbine buffer/spring on my 10.5" and 7.5". With the 7.5" however, we made the gas hole larger. I don't remember the exact size, a friend has a chart that he uses from experience for it to cycle reliably. Depends what you're doing with the gun but if it's going to be more than a range toy I'd go with the 10.5" (even though the 7.5" looks very cool).
You do eat quite a bit of gasses with the 7.5" (of course that might be because I'm left handed and my face is behind the ejection port.

 

[C-grunt]

I would avoid any sort of legal questions and just buy a proper pistol receiver extension. They are not very expensive.

As for the barrel length I would highly suggest the 10 inch barrel over the 7. It will be much easier to get it to run right and have better ballistics.i would also look seriously at a 11.5 inch barrel. You get a lot more dwell time which results in a more reliable rifle.

 

[Fishbed77]

It will be much easier to get it to run right and have better ballistics.i would also look seriously at a 11.5 inch barrel. You get a lot more dwell time which results in a more reliable rifle.

BCM makes a big deal of the dwell time issue, But LWRC and DD have had no issues making reliable 10.5" barreled ARs (not to mention the military Mk.18 CQBR).

Personally, I've built a 10.5" AR pistol, and I've never had a single malfunction with it, and that's with a wide variety of ammo, incuding M193, M855, and steel-cased Russian junk.

 

[C-grunt]

Daniel Defense also has very oversized gas ports on their Mk18 which causes it to be overgassed when using 5.56 spec ammo.

LWRC also uses a piston system which is much less effected, or easier to tune for, by barrel length than DI systems.

 

[Warp]

I agree with the un-requested advice of use a pistol receiver extension (buffer tube). Unless you want to potentially be the test case.

I also agree with 11.5" being an excellent choice for a 5.56x45 upper.

 

[C-grunt]

Also just because the design is less reliable doesnt mean individual weapons are un reliable.

When the USMC tested the M4 against the M16A4 they found the M4 to be considerably less reliable than the rifle. However this is over several weapons and tens of thousands of rounds. However the M4 has served both the Army and Marine Corps very well in the last 13 years.

 

[Warp]

Also just because the design is less reliable doesnt mean individual weapons are un reliable.

When the USMC tested the M4 against the M16A4 they found the M4 to be considerably less reliable than the rifle. However this is over several weapons and tens of thousands of rounds. However the M4 has served both the Army and Marine Corps very well in the last 13 years.

Also worth considering, when was that test done and is a current quality 'M4' the same as that one?

It's too bad they went with the carbine gas instead of mid length though, from my perspective anyway, which is a meaningless one I know

 

[C-grunt]

Also worth considering, when was that test done and is a current quality 'M4' the same as that one?

It's too bad they went with the carbine gas instead of mid length though, from my perspective anyway, which is a meaningless one I know

Im pretty sure it was the current M4. The info is on M4C.net and comes form a USMC official in the know. Like I said it doesnt prove that the M4 is unreliable but that the rifle is just more reliable.

 

[MistWolf]

I would avoid any sort of legal questions and just buy a proper pistol receiver extension

The RE is NOT a stock. What RE used on your pistol does not matter so long as you don't install a rifle stock. If the RE is bare, that is, you don't have something like a Sidesaddle or Arm Brace installed, having a spare stock that will fit the RE in the same vicinity could be construed as constructive intent

 

[C-grunt]

The RE is NOT a stock. What RE used on your pistol does not matter so long as you don't install a rifle stock. If the RE is bare, that is, you don't have something like a Sidesaddle or Arm Brace installed, having a spare stock that will fit the RE in the same vicinity could be construed as constructive intent

That last sentence is exactly why I just buy a proper pistol RE that won't fit a stock at all.

 

[pjeski]

If you slip a stock over a pistol tube, you have every bit as much made an sbr as if it were over a carbine tube. There is nothing that requires the stock be latched in to be a stock for the weapon to be considered an sbr.

There is no reason not to use a carbine stock on a pistol, other than that you have to be careful to avoid constructive possession. You could be just as guilty with your pistol tube installed if you have a spare carbine tube and stock, an no other practical use for them but to build an sbr.

 

[USAF_Vet]

Well I don't have another stock. The receiver extension tube kit does not come with a stock, just the tube, retainer, spring and buffer. The only stock I have is still mounted to my AR carbine, so I should be good if a random ATF agent comes by with a warrant to search my home, I shouldn't get saddled with an add-on charge of constructive possession. Which even if they tried, I still haven't purchased a pistol upper, so it wouldn't make a lick of difference if I did currently have a stock. Without a short barrel upper, a constructive possession charge couldn't stick.

As yet, I'm currently undecided if I'm going the pistol route, or just build it up as another rifle. The pistol was my original intent, because of the ATF ruling that a pistol can be built into a rifle and converted back to a pistol at any time. And if registered to the state of Michigan as a pistol, then converted to a rifle, I should be able to carry it loaded in a vehicle as a backdoor into the grandfathered "Michigan Pistol long guns." Not that I really want any of my guns registered, though. Which is the one drawback of building it as a pistol.

 

[MistWolf]

That last sentence is exactly why I just buy a proper pistol RE that won't fit a stock at all.

That's why I just installed an SB15 arm brace and called it a day. A 10.5 inch upper runs great with a rifle RE assembly

 

[pjeski]

Well I don't have another stock. The receiver extension tube kit does not come with a stock, just the tube, retainer, spring and buffer. The only stock I have is still mounted to my AR carbine, so I should be good if a random ATF agent comes by with a warrant to search my home, I shouldn't get saddled with an add-on charge of constructive possession. Which even if they tried, I still haven't purchased a pistol upper, so it wouldn't make a lick of difference if I did currently have a stock. Without a short barrel upper, a constructive possession charge couldn't stick.

As yet, I'm currently undecided if I'm going the pistol route, or just build it up as another rifle. The pistol was my original intent, because of the ATF ruling that a pistol can be built into a rifle and converted back to a pistol at any time. And if registered to the state of Michigan as a pistol, then converted to a rifle, I should be able to carry it loaded in a vehicle as a backdoor into the grandfathered "Michigan Pistol long guns." Not that I really want any of my guns registered, though. Which is the one drawback of building it as a pistol.

In MI, it has to be registered in a configuration <26" and it has to be in a configuration <26" to carry it as a pistol. I have ARs in rifle configurations that I built as pistols first. The only way I can carry them as pistols is if they are <26", with or without a stock. (< or = I think, but I stay away from =)

 

[sappyg]

There is no reason not to use a carbine stock on a pistol, other than that you have to be careful to avoid constructive possession. You could be just as innocent with your pistol tube installed if you have a spare carbine tube and stock, an no other practical use for them but to build an sbr.

Fixed that for you.

 

[pjeski]

Fixed that for you.

True enough.

 

[USAF_Vet]

I know when the "Michigan pistol long gun" thing was still a law, a folding stock AK with the stock folded was <26", and thus registered as a pistol. Although it was still a rifle, it could be transported, loaded, as a pistol due to the way the law was written. Since the law was repealed, those registered long guns were grandfathered and could still legally be carried/ transported as a pistol provided they stayed registered. Since there is no way to unregister a firearm, anything registered falls under the law.

And since the law registered all long guns between 26" and 30" at its shortest configuration, this included most AR carbines with collapsible stocks, PGO shotguns, folding stock carbines, etc.

 

[Warp]

I still can't believe Michigan now openly "registers" all handguns. Of course, I couldn't hardly believe the safety inspection thing in the past either.

PA isn't much better.

 

[pjeski]

I know when the "Michigan pistol long gun" thing was still a law, a folding stock AK with the stock folded was <26", and thus registered as a pistol. Although it was still a rifle, it could be transported, loaded, as a pistol due to the way the law was written. Since the law was repealed, those registered long guns were grandfathered and could still legally be carried/ transported as a pistol provided they stayed registered. Since there is no way to unregister a firearm, anything registered falls under the law.

And since the law registered all long guns between 26" and 30" at its shortest configuration, this included most AR carbines with collapsible stocks, PGO shotguns, folding stock carbines, etc.

Shortest operable configuration. And that's still true. All I'm saying is you can't build a <26" rifle, register it as a pistol, then throw a full length upper on it and carry it in your truck in Michigan. It has to be in a pistol configuration (shortest operable) to do so.

Also, there is a way to "unregister" an old Michigan pistol (> 26" < 30") if you no longer want it to be considered a pistol. It doesn't remove it from the registry per se, but simply records your declaration that you no longer treat it as a pistol, if I understand it correctly.

RI-44 http://michigan.gov/documents/msp/ri-044_406611_7.pdf

 

[C-grunt]

That's why I just installed an SB15 arm brace and called it a day. A 10.5 inch upper runs great with a rifle RE assembly

True that. I was very skeptical about the SB15 but I'm glad I bought mine. I'm still going to get a stamp for it but for people who don't want to go through that hassle it is a great 2nd option.

 

[MachIVshooter]

If you slip a stock over a pistol tube, you have every bit as much made an sbr as if it were over a carbine tube. There is nothing that requires the stock be latched in to be a stock for the weapon to be considered an sbr.

Many pistol tubes are too large for a stock to fit over them.

Having said that, nothing wrong with the OP's plan to mill off the key slot protrusion. It'd be pretty tough to argue that you intend to put a stock on after modifying the tube in such a way that any actual stock would be able to rotate 360* freely, and would slip off the end when you tip the muzzle up.

It's how I did mine while waiting on my stamp, as I saw no reason to spend more on a temporary tube when I had extra carbine tubes lying about.