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Old December 22, 2010, 12:21 PM   #1
Blackops_2
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AR Buffer tube question.

Been looking at stuff for a future project and i'm one to prepare early and do all my research and stuff. Well since i'll be getting my lower and carbine AR built in a couple weeks or so. I was thinking about sometime later next year getting a Stag Super varminter upper and a magpul PRS stock. But i noticed at bravo company the stock will need a A1/A2 Rifle receiver extention (buffer tube), a A1/A2 Rifle Buffer, and a A1/A2 Rifle Buffer Spring to mount to your stripped receiver. But i also read changing buffers should be done by a gun smith. So i'm guessing it's something i can't do on my own or what? I might have misread, but i didn't think changing buffer tubes would be hard.
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Old December 22, 2010, 12:37 PM   #2
DnPRK
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Changing or installing a buffer tube does not have to be done by a 'smith.

You will need the buffer detent and spring and an adjustable crescent wrench. I like to use a little anti-sieze on the threads to prevent galling (so I can remove the rifle tube and install a carbine tube at a future date).
  1. Screw the tube in by hand until it seats.
  2. Back it off half a turn and install the detent and spring.
  3. Depress the detent while tightening the tube, trapping the detent's shoulder under the tube's lip.
  4. Torque the tube with the crescent wrench using the flats at the end of the tube.
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Old December 22, 2010, 12:55 PM   #3
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Thanks for the info that saves some money. Cause i didn't want to have to buy a new lower and pretty much build a entire new rifle when i can just use my BCM lower. Especially when all i'm doing is changing the stock and upper.
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Old December 22, 2010, 03:29 PM   #4
10mmAuto
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If you intend to keep using that lower with your carbine upper, know this - the carbine length gas system runs at around twice the pressure of a rifle length gas system. Don't put the carbine upper on there with a rifle buffer tube/buffer/spring.
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Old December 22, 2010, 03:40 PM   #5
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If you intend to keep using that lower with your carbine upper, know this - the carbine length gas system runs at around twice the pressure of a rifle length gas system. Don't put the carbine upper on there with a rifle buffer tube/buffer/spring.
ABSOLUTE NONSENSE. The Rifle buffer is infinitely better with a carbine upper. The Carbine buffer system is a compromise to get the size down, and has historically been MUCH more problematic than the rifle buffer system.

In fact one of the Sheriff's Office instructors had his old SWAT entry gun set up with a 10.3" upper on a DRMO M16 lower with the rifle buffer. SBRs really gain smoothness in operation from a rifle buffer system.

If you want a sweet running carbine, get the rifle buffer system. And now with VLTOR's A5 stock, we can have the best of both worlds. A collapsible stock with a rifle buffer spring and shorter Rifle weight buffer.

Also, the the carbine gas system does NOT run "at around twice the pressure". It runs at a higher port pressure, but it's not twice the amount.
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Old December 22, 2010, 04:54 PM   #6
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Well technically it's a Mid length gas system, for the carbine upper. But i intend on having the carbine stock on the carbine buffer and the PRS stock on the rifle length and changing them according to upper. Which will be between my 14.5 mid and the 24" stag varminter..
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Old December 22, 2010, 05:00 PM   #7
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Really building another lower isn't that much money. I'd consider it since you are planning to have the carbine and rifle stocks and two uppers. All you'd be out is maybe $150 for a stripped lower and a LPK. And you wouldn't have to keep swapping the stocks.

Best of all, for $150 or so more you'd have two complete ARs!
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Old December 22, 2010, 05:04 PM   #8
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Sounds like a good idea, but does a stripped lower have to go through a FFL? Thats the only reason i'm considering this plan with 2 stocks and 2 uppers. Because once this BCM upper gets in i wont feel like going through the FFL again, it annoys me going through FFL for stuff, although thats just how it is. Need to look into gettin a FFL however i do it..
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Old December 22, 2010, 05:42 PM   #9
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If you don't like the FFL paper, you can always wait until you find a private seller in your area and it's perfectly above board.
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Old December 22, 2010, 05:55 PM   #10
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Well i have sellers in my area, just they don't carry BCM. And i wont settle for another lower i like BCM too much.
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Old December 22, 2010, 06:02 PM   #11
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Yeah...that's kinda silly. They're no different than a $60 SurplusAmmo.com lower apart from the rollmark.
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Old December 22, 2010, 06:22 PM   #12
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I'd be particular too as I have my own favorites, but I wouldn't limit myself to BCM only.
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Old December 22, 2010, 06:30 PM   #13
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I have a CMMG lower with a DPMS parts kit in it, nothing fancy, all mil-spec stuff but it does what it's supposed to. BCM is a good company, but not the only good company.
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Old December 22, 2010, 06:47 PM   #14
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I didn't mean BCM was the only good company not at all. That's just the lower I've picked out. Yeah the statement I said is rather silly, I couldve worded it differently so my bad as it was a silly statement but BCM is what I've settled on for my lower. My 24" upper I plan on gettin won't be BCM. Its also a full lower assembled, not just the reciever. But if I were to get the parts from scratch and just build another lower, I'm guessing some parts still have to go through a FFL?
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Old December 22, 2010, 07:36 PM   #15
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A lower is pretty much a lower. I got an Armalite just because I wanted my rollmark to say ArmaLite.
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Old December 22, 2010, 10:49 PM   #16
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Also, the the carbine gas system does NOT run "at around twice the pressure". It runs at a higher port pressure, but it's not twice the amount.
It is in fact twice the amount. Its a lot higher at the carrier too.

http://www.armalite.com/images/Tech%...4%E2%80%A6.pdf

Just because you know of one guy who feels like their weapon is running smoothly doesn't mean it in fact is and demonstrates the soundness of the concept on a wide scale. At the very least their weapons internals are pummeling the **** out themselves every time they fire and they are more likely to have serious failure in the weapon eventually. The Army actually put out additions to many FMs because some Joes did this and had catastrophic failures. Please do your research before you rudely dismiss something "ABSOLUTE NONSENSE".
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Old December 23, 2010, 08:30 AM   #17
Bartholomew Roberts
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Don't put the carbine upper on there with a rifle buffer tube/buffer/spring.
The rifle buffer weighs 5.2oz and is considerably heavier than even an "H2" buffer and has a longer action spring as well. In my experience, a rifle buffer with a carbine upper usually performs better, not worse.

Quote:
At the very least their weapons internals are pummeling the **** out themselves every time they fire and they are more likely to have serious failure in the weapon eventually.
When buffer weight isn't perfectly matched to the use, you can get what is called "bolt bounce." The bolt slams into the chamber hard enough that the bolt actually rebounds from the receiver a little bit. If the action spring is in perfect condition, this is less of an issue with any buffer weight but as the action spring wears, buffer weight (and more importantly buffer design) become more critical in preventing this. The thing about bolt bounce is that the firearm may function perfectly even though there is considerable rebound going on, so it isn't always obvious when it happens.

First try this a very interesting link from Vuurwapenblog.com. It describes the phenomenon and demonstrates it well using high-speed video. In the video, you can see how the carbine buffer (2.9oz) in a carbine gas system allows a certain amount of bolt bounce. You can also see that the much heavier 9mm buffer (5.5oz) allows almost the same degree of bounce. However, the H buffer, even though it weighs only 3.9oz virtually stops bolt bounce. This is because unlike the 9mm buffer (but like the carbine buffer), it has sliding internal weights. The combination of slightly more weight with the sliding weight design solves the problem.

Next, check out this high-speed video comparing carbine/H/H2/rifle buffers in 16" midlength and 16" carbine gas systems. It illustrates very well that the rifle buffer and action spring is sufficient to prevent bolt bounce in a 16" carbine upper.

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The Army actually put out additions to many FMs because some Joes did this and had catastrophic failures.
That is news to me. Could you point me towards the Army publications that address these issues?
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Old December 23, 2010, 10:23 AM   #18
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Like as not the changes were to TM's, not FM's. There is a difference. And the Army not liking it probably had as much to do with jacking up their serial number inventory by MODEL that is required monthly. You can't just trade off uppers and lowers at will, it creates a huge accountability problem for commanders.

If he's signed for 100 M16A2's and 100 M4A1's, how do you count a hybrid A2 lower with an A1 carbine upper - when it doesn't officially exist?

Does Joe Snuffy know not to swap the buffers? A rifle buffer in the carbine is not a good thing. Neither is the reverse.

It sounds like a lot more of a problem with "Leave well enough alone." Building an AR right now, I have a completed rifle lower - which will get a 6.8 midlength upper, and it's a known good combination for exactly the reason the Army is buying the Vltor stock. The rifle buffer system has less trouble and always has been more reliable than carbine, regardless of barrel length.

Looking forward to the Change No. on the specific manual it alters.
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Old December 23, 2010, 11:31 AM   #19
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Tirod, is it hard to build a lower from a parts kit and all?
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Old December 23, 2010, 11:43 AM   #20
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Tirod, is it hard to build a lower from a parts kit and all?
It's a piece of cake. BCM is good stuff, but I wouldn't go nuts for a BCM lower... the uppers are where stuff *really* matters. Not that complete crap is fine for the lower, but there's much less difference, especially for the stripped lowers themselves.

I've assembled 3 lowers, the first time out it took me less than a half hour. There are differences between LPK quality levels, but they aren't huge. Of the ones I've installed, I have a preference for RRA; their roll pins have tapered edges so they go in more easily than the DPMS kits I've used (I do have a DD kit, but haven't installed it into anything yet). There's plenty of instructions out there for you on the internet- the only places where people tend to screw up are launching the front takedown pin detent across the room, scratching the finish as they hammer pins home, and busting off a trigger guard ear because they didn't support the backside.
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Old December 23, 2010, 11:49 AM   #21
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I see. I was looking at the kits they offered @ bravocompany and saw stag, DPMS, and RRA. It's so much cheaper to assemble one it's unreal.. i'm rather dumbfounded actually. Good to hear it's not too bad. With enough reading i should be able to get the hang of it. Not going to rush into anything, but i definitely know i'm going to build one rather than buy it assembled. I build my own computers although i'm not that mechanically inclined, i know a gun and a computer are too vastly different things haha, but i'll look into it. Thanks for the insight.
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Old December 23, 2010, 11:59 AM   #22
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This Arfcom thread has the walkthrough I used when I built mine.

For the front takedown pin, my method was simple- I clamp the lower in a vise (padded, mind you), and I stick the spring in the hole. Then I take a set of precision-sized needlenose pliers and hold the detent in position. I use the small end of the takedown pin to push the detent into place (basically pointing the pin along the axis of the lower), then rotating the pin 90 degrees for insertion into the lower. Done right, it traps the detent and keeps it from flying off.

Other guys have been known to do this in a bag or the bathtub (drain closed, curtain drawn) to keep the thing confined, but I've never had a problem.
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Old December 23, 2010, 12:08 PM   #23
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Thanks for the link, will definitely have to start reading. I also more than likely see if my dad wants to help. He's really mechanically inclined. For instance i had a broken paintball gun when i was young. Him not knowing anything about them took the entire thing apart and fixed it, then put it back together..Idk how people like him do it haha. I got to looking at lower recievers and i notice a good bit of reviews coming from Spike's tactical. Then i saw a Billet lower with a biohazard symbol on it that comes with all the assembly parts. This is the child coming out in me but it looks downright awesome with the biohazard symbol..
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Old December 24, 2010, 09:16 AM   #24
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It is in fact twice the amount. Its a lot higher at the carrier too.

http://www.armalite.com/images/Tech%...4%E2%80%A6.pdf

Just because you know of one guy who feels like their weapon is running smoothly doesn't mean it in fact is and demonstrates the soundness of the concept on a wide scale. At the very least their weapons internals are pummeling the **** out themselves every time they fire and they are more likely to have serious failure in the weapon eventually. The Army actually put out additions to many FMs because some Joes did this and had catastrophic failures. Please do your research before you rudely dismiss something "ABSOLUTE NONSENSE".
Oh I've done my research, Jethro. Try playing with Quickload and getting some facts. Try looking at a pressure curve chart and tell me that the pressure is double. I just doesn't work that way.

It's not even debateable that the rifle buffer runs smoother... ON ANY AND ALL gas systems. Running a carbine upper and the standard carbine buffer is what beats a gun senseless. If you can explain to the rest of the world how a heavier buffer on a less compressed spring stroke equates to a gun running harsher, you can defy basic physics. And try selling that idiotic notion to any of the engineers who post on the various forums from time to time.

Armalite's silly website is long out of date... just like armalite's product line. They've been long left in the dust. Maybe 10 years ago the best info we had on the AR was Armalite's site, but we have good, and real info available to us now. I'd never site a company who uses CLAMP ON front site bases as the official word on AR matters.

Last edited by demigod; December 24, 2010 at 09:26 AM.
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Old December 24, 2010, 09:18 AM   #25
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That is news to me. Could you point me towards the Army publications that address these issues?
I'd love to see this too!
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