AR Pistol Buffer Tube

[Oh Shoot]

So, have toyed with going pistol with one of the AR lowers I bought for no particularly good reason.

To keep me from actually learning something by doing my own research , I ask the following:

Most all I see use the conventional rifle buffer tube like:

Once in a while I see one quite a bit shorter, like this; seems to be about the shortest you can get?

So question is, I assume the shorter one simply has stronger and shorter spring in there, but which begs the real question:

why aren't there any even shorter than that, with just shorter stronger spring?

- OS

Edited September 24, 2012 by OhShoot

[MacGyver]

Bolt carrier group still has to have room to cycle.

[Oh Shoot]

edit: Big duh, I get it, Mac, wasn't thinking, thnx.

- OS

Edited September 24, 2012 by OhShoot

[Oh Shoot]

nm, continued stupidity by double tapping

Edited September 24, 2012 by OhShoot

[MacGyver]

^{Solve this problem in a direct impingement rifle and I'm sure you could retire rich after all the arfcom guys empty their wallets in your direction.}

^{BTW...even us engineers have the occasional day like this. Nothing humbles you quite as much as drawing something up only to have a machinist ask "how exactly do you expect this to work?"}

[Oh Shoot]

BTW...even us engineers have the occasional day like this. Nothing humbles you quite as much as drawing something up only to have a machinist ask "how exactly do you expect this to work?"

For some absurd reason while considering this, I simply had a vision of bolt just moving inside the carrier, totally disregarded hard fact that carrier has to come back into the tube.

Yes, I've taken them apart.

- OS

Edited September 24, 2012 by OhShoot

[Lumber_Jack]

Yeah if you want shorter you gotta buy a RRA PDS

http://www.rockriverarms.com/index.cfm?fuseaction=category.display&category_id=441

But I think it's only available as complete gun.

[Dolomite_supafly]

Part of the spring recoils into the carrier in the shorter version if I remember correctly. It also has a shorter bolt carrier as well if I remember. It has been a while since I messed with one.

Dolomite

[Guest 6.8 AR]

There is a shorter carrier out there, somewhere. I like that long buffer tube with the foam cover. Rest the

cover on my shoulder and I can occasionally hit something.

With the limited use of the pistol variant, I don't care about the buffer being so long. They are hard enough

to find, as it is.

[Erik88]

Here is what I don't understand. What advantage does the above rifle have over my M&P Sport other than the ability to conceal? You can't exactly put that up to your shoulder and expect it to be comfortable?

[Lumber_Jack]

I personally wouldn't have one in 5.56. I'm building one in 300 BLK in 9-10" so that when I get a supressor it's overall length will be manageable. It save a $200 stamp for an SBR

[Guest Aces&8s]

So far, I am loving my 5.56 AR pistol. It is a blast to shoot, and once I figured out that it likes to run on the wet side, it has been flawless. OS, I went with the Doublestar buffer tube, which uses a carbine spring, and I swapped out the buffer for an H2, and it does just fine with .223 and 5.56 rounds.

Sent from my NookColor using Tapatalk 2

[Guest 6.8 AR]

I personally wouldn't have one in 5.56. I'm building one in 300 BLK in 9-10" so that when I get a supressor it's overall length will be manageable. It save a $200 stamp for an SBR

And that is a big advantage. I'm actually thinking of the Blackout, now.

But don't tell Caster!

[Guest 6.8 AR]

It's a trunk gun, Erik. BTW, it isn't uncomfortable at all.

[Oh Shoot]

So far, I am loving my 5.56 AR pistol. It is a blast to shoot, and once I figured out that it likes to run on the wet side, it has been flawless. OS, I went with the Doublestar buffer tube, which uses a carbine spring, and I swapped out the buffer for an H2, and it does just fine with .223 and 5.56 rounds.

Does look rather cool.

[Oh Shoot]

It's a trunk gun, Erik. BTW, it isn't uncomfortable at all.

I was thinking it would go nicely with single point sling under a full length leather coat. I already have the coat and a lower.

- OS

[Guest 6.8 AR]

Now you're accessorizing. Very good fashion statement.

[Oh Shoot]

Now you're accessorizing. Very good fashion statement.

- OS

[Defender]

What about the Keltec PLR-16? That one has no buffer tube at all. Is it piston driven?

Personally, I really like the one with the foam padded buffer tube like the RRA one I saw. Seems like it would function a lot like a SBR.

Edited September 25, 2012 by barewoolf

[Guest 6.8 AR]

- OS

Now that's a badass!

[Oh Shoot]

What about the Keltec PLR-16? That one has no buffer tube at all. Is it piston driven?

Yeah, it is, but not in the same sense as a conventional piston driven AR, which still needs a buffer tube and spring.

Looking at PLR exploded view, I can't quite see how the bolt gets back into battery, though. Seems quit different from say, the Mini14 "fixed piston" operation.

- OS

Edited September 25, 2012 by OhShoot

[RichardR]

Regardless of caliber you'll actually want the longer carbine buffer tube, preferably one that has foam covering so that even without a stock on it they can be sort-of shouldered and you can get a decent/stable sight picture, this is even easier if you use a holosight.

The shorter tubed & piston varients you have to use a sling, fully extend the weapon creating a nice tight lockup against the sling in order to keep the weapon stable enough to sight down the sights/hit anything.

The muzzle blast from a 7.5" 5.56x45mm is extremely harsh though, so double up on your hearing protection, recoil isn't that bad but the bark is truely impressive something to behold.

While they are definately head turners at the range, other shooters can not only "feel" the blast from several lanes away they are loud enough that they will make ears ring even if they are wearing good hearing protection, so make sure to be as considerate to others as possible when taking them out to a public range.

Other than that, reliability seems to be really good if you run them wet, in fact I have never had a malfunction that I can recall, they make a nice portable package & they will fit into most gym bags, of course the shorter the barrel gets the more that the outputted power is diminished but they still are really nasty lil buggers within 75-100 yards.

Some guys prefer to use heavy gr bullets in theirs but I have found that that 55gr FMJ in a short 7.5" 1/7 twist rate barrel are just stable enough to accureately reach out to 75-100 yards while retaining just enough velocity to still tumble & fragment.

[Guest Lester Weevils]

Yeah, it is, but not in the same sense as a conventional piston driven AR, which still needs a buffer tube and spring.

Looking at PLR exploded view, I can't quite see how the bolt gets back into battery, though. Seems quit different from say, the Mini14 "fixed piston" operation.

- OS

I'm not good explaining mechanisms. Its easier to see taking the thing apart than looking at the pictures. The outside tube is the Piston Recoil Spring tube. When assembled, that tube is pushed into the gas head on the front and fixed against the receiver in the back so it can't move. The spring surrounds the piston rod that rides inside the tube. When the bolt is in battery the spring is partially compressed inside the tube, pushing the piston rod fully forward, and the piston rod is firmly attached to the bolt carrier, so the spring also pushes the bolt carrier fully forward. When gas drives the piston rod back (and also drives the attached bolt carrier back), it compresses that captive spring even more, so after the ejection and gas pressure equalizes, the compressed spring pushes the piston rod forward with some energy, and the piston rod drags the bolt carrier along with it, loading the next round and slamming the bolt into battery. It is a rotating bolt that cams into a lock with lugs in the chamber, in the final fraction of an inch of forward motion.

Edited September 25, 2012 by Lester Weevils

[Oh Shoot]

....and the piston rod is firmly attached to the bolt carrier, ...

That's the part I couldn't grok looking at exploded view, how the rod attaches to bolt carrier so it can pull it back into battery after the shot, looks like it just sticks into it and would go back forward leaving carrier/bolt in the open position. Don't see any pin or anything shown that would hold them together.

Mini14 has the spring behind action bar (which they call "slide assembly", what the charging handle is part of) which locks into bolt, so it's quite obvious.

- OS

Edited September 25, 2012 by OhShoot

[Guest Lester Weevils]

That's the part I couldn't grok looking at exploded view, how the rod attaches to bolt carrier so it can pull it back into battery after the shot, looks like it just sticks into it and would go back forward leaving carrier/bolt in the open position. Don't see any pin or anything shown that would hold them together.

Mini14 has the spring behind action bar (which they call "slide assembly", what the charging handle is part of) which locks into bolt, so it's quite obvious.

- OS

Yeah I got out the PLR-16 and also looked over the little printed manual that has a pretty good sequence of photographs of assembly/disassembly, but didn't tear it down again before posting the message. Have taken it apart a few times for cleaning. Can't recall how the piston rod is attached to the bolt carrier, whether it is pinned in or something else.