View Full Version : Bushmaster buffer question
I had a buffer retainer defect while at the range today. In attempting to figure out what the issue was (is) I noticed the buffer itself, at the end that contacts the buffer retainer is not round all the way. It was designed with three flat sides. I am supposing that afte firing for a bit, that one of the flat sides of the buffer worked its way around to the bottom where the small post of the buffer retainer is and thus did not engage the buffer retainer completely and consequently jumped it.
Anyone with this issue? Is this a design flaw?
It's suppossed to have flats. There is no design flaw. Something isn't right. The buffer shouldn't even touch the retaining pin when the action is closed.
The back of the carrier pushes the buffer back and takes the tension off of the retaining pin when the actions are closed.
Thanks for your reply. It all looks normal. Guess I'll pop in a new retainer and see what happens.
Is the retainer damaged?? Can you get pics of any problems?
The retainer is sheared partially at about a 45 degree angle at about the top 16th of an inch, just one side.
I see what I can do about a picture.
What are the flats for anyway?
The flats are there to prevent the buffer from having too of a seal in the receiver extension/buffer tube.
I've never seen a retaining pin bend like you describe. Ususally the pin's hole in the lower gets egged out from getting banged by the buffer face.
What's your email, I'll send a picture.
I pm'd it to you. Can you attach it to your reply here or host it? I'd like Iraqgunz and the gang to be able to see it.
Post the photo here.
I have a crappy Bushmaster too and I'd like to see JIC.
Best I could do was an email to your ATT mail
is this a collapsible stock?
The pic is blurry and only of the damaged pin. I'd kinda like to see the buffer area of the gun, or maybe the back of the bolt group in the upper.
The damage is done to the pin, but the question is why. The retaining pin should never have enough force on it to do that.
I'm wondering if the bolt carrier didn't smack it some how. :confused:
I'm wondering if when I installed the UBR, I didn't tighten the tube completely. I say that because I noticed that when I was checking it out, I noticed there was a small dented, not that bad, on the tube in the area of the buffer retainer pin. Upon reinstalling, that little dent area was a half turnpast when it was. In other words, the tube was not tightened completely allowing the buffer retainer to move up further that it should have. Pics to follow.
Hope this makes sense
In other words, the tube was not tightened completely allowing the buffer retainer to move up further that it should have. Pics to follow.
Hope this makes sense
That's possible. I'm not familiar with the UBR. It has a proprietary tube doesn't it?
Pic #2 almost looks like there's damage to the buffer retaining pin hole.
Is the buffer tube just barely touching the edge of the retaining pin (when its in)? It does look like maybe you should have given it one more turn.
UBR does have a prop tube but it fits exactly as the OEM. I believe the top corners of the second thread have been knocked off. Crap, I hope thats not going to be a major issue in the stability of the buffer retainer.
Unfortunately the pics are crap. In any case if you have damage to the retainer pin, something isn't assembled correctly.
You need to ensure that the tube is torqued properly and that you assembled everything correctly.
If you are 100% sure then your lower could be out of spec. Again this is all speculation without better pics.
Looking at the one pic of the buffer retainer pin hole where it is chewed up something tells me that there is something more going on.
So before we play 100 more questions please tell us what lower you have, which upper, what type of bolt carrier, etc...
Is it possible the pin wasn't properly retained, because the buffer tube wasn't threaded in enough, and it "popped out" and was pushed into those front threads forcefully by the BCG, damaging the lower?
It's been awhile since I installed a UBR. IIRC it uses a rifle type buffer tube. Once it is secured, part of the stock slides forward and rests inside the hole at the rear of the lower receiver. It is then secured by a screw at the rear that has thread lock applied to it.
In order for that to happen, I believe that the whole thing would have had to be installed improperly because I don't believe that the tube can turn.
Is it possible the pin wasn't properly retained, because the buffer tube wasn't threaded in enough, and it "popped out" and was pushed into those front threads forcefully by the BCG, damaging the lower?
yeah Heidevolk....I think that have been what happened.
Iraqguns.......I am sure it was a half turn short looking at it.
Belmont31R
09-29-11, 15:18
Yeah its the same principle as an A1/A2 extension.
Most stock wrenches have a little egg shaped cut out on them you use on the back of the tube to tighten it like a socket wrench basically. When I installed mine I put a very small drop of blue loctite on the extension threads (after wiping them off with acetone both on the extension and receiver). Then the stock body is slid onto the extension, and you put the screw in through the body into the extension. The screw should have blue loctite, too. Then the lower half of the stock is installed.
So make sure the extension and screw are secure next time, and use the stock wrench on the back of extension. You don't have to gorilla strength it in place but fairly snug, and make sure the retaining pin cannot come out yet still moves freely within the hole.
Thanks to all you guys for your help. I believe I'm back in business.
Gonna go ahead and get a new a buffer retainer and spring and head back to the range. sure wish I lived out in the country so I could just go to my back porch and shoot.
OH well, have a great day and thanksw again.
Jerry
Doesn't the stock come with instructions? Also, doesn't the tube have a lip around the threaded area? I am pretty sure it does. When you tighten it that lip needs to be flush against the lower reciever.
Make sure that you use the correct wrench for the tube. I have seen some that got chewed up because they used something else.
Iraqguns.......I am sure it was a half turn short looking at it.
Image Group
11-30-11, 02:07
Same thing happened to my Bushmaster and a friends. I replaced my pin with an aftermarket and never had the issue again as did my friend. I did take the time to compare the aftermarket pin with the BM pin and I'd have to say it seemed quite a bit cheaper build quality and not built for longevity. My 2 cents.
If you are 100% sure then your lower could be out of spec. Again this is all speculation without better pics.
This would be my guess...look how far forward his retaining pin hole is drilled. His RE looks to be screwed all the way in (it's pretty much flush with the receiver) and yet still barely covers the retaining pin hole. I also would guess this would lead to retaining pin damage which in turn leads to the pin then slamming into the forward end of the pin hole, which might be part of the explanation why the receiver is chewed up, as IG noticed.
His
http://i163.photobucket.com/albums/t294/myersma2/a389b20e.jpg
Example for comparison
http://i163.photobucket.com/albums/t294/myersma2/4ee91b7b.jpg
ETA: **** me...looks like my buffer tube is cracked.
I ended up replacing the pin with one from DPMS. Guess we will see. Tahnks for all the comments :)
http://i163.photobucket.com/albums/t294/myersma2/4ee91b7b.jpg
ETA: **** me...looks like my buffer tube is cracked.
Sure does look that way!
C4
yeah, that's as far as you can tighten it, any more and the LRE will hit the upper. ETA: totqlly looking at the wrong picture.
I think I posted the dimension from the buffer detent hole to the rear (?) of the lower in another thread.
http://i163.photobucket.com/albums/t294/myersma2/4ee91b7b.jpg
Sure does look that way!
C4
ETA: no cracks..just mark left either left by their finishing or the buffer movement. They offered to replace it anyway. I'm fine with it but great CS!
http://i163.photobucket.com/albums/t294/myersma2/0ca41e3b.jpg
In my amateur opinion that lower appears to be aout of spec.
Sorry - OPs or mine? :confused:
I don't know because of all the quoting of pics.
Sorry - OPs or mine? :confused:
His
http://i163.photobucket.com/albums/t294/myersma2/a389b20e.jpg
Mine
http://i163.photobucket.com/albums/t294/myersma2/4ee91b7b.jpg
I don't know because of all the quoting of pics.
Yes, his.
His
http://i163.photobucket.com/albums/t294/myersma2/a389b20e.jpg
Mine
http://i163.photobucket.com/albums/t294/myersma2/4ee91b7b.jpg
This would be my guess...look how far forward his retaining pin hole is drilled. His RE looks to be screwed all the way in (it's pretty much flush with the receiver) and yet still barely covers the retaining pin hole. I also would guess this would lead to retaining pin damage which in turn leads to the pin then slamming into the forward end of the pin hole, which might be part of the explanation why the receiver is chewed up, as IG noticed.
His
http://i163.photobucket.com/albums/t294/myersma2/a389b20e.jpg
Example for comparison
http://i163.photobucket.com/albums/t294/myersma2/4ee91b7b.jpg
ETA: **** me...looks like my buffer tube is cracked.
This is why I'm glad, and also proud to have an LMT made lower. Absolutely 0 probability of this being off, as each of the LMT lowers are 100% checked with veneers before leaving the factory for every critical ordeal. Great QC means great products. I have seen 1 DPMS with a wacked brp, and also one spikes with the same. Saddening to see such a basic ordeal be messed up. Either way, it's not like you truly need the BRP for the gun to function fine. In fact, I only just installed mine. Never had a reason to install mine being I was changing springs left and right to find that sweet spot for my blow back 5.7 upper (and thanks to the troy mount, I never had to stake my castle nut) (save thumb numbing, or screw-drivering each time. Consider I had 20 springs to swap, test etc. To note I was also one of the ones testing the original AP bolts out, so why bother with a BRP when I could just stop it from sliding out with my thumb. I am also currently testing new buffers as well [non A/P made].
One pic of his looks like his BRP was chewed up on the side, probably from the bolt slamming it around, and one pic looked like a heavily ovalized hole, which also could be the reason. I had a buddy with an ace stock identical to mine thread the CRE into the receiver right into the BRP and it bent the hell out of the RE, but I couldn't imagine how much force it would take to ovalize a BRP hole. It either came like that, or took a breaker bar to do. Aluminum compresses, but my god, it takes a whole lot to compress solid aluminum, especially when using basically a hollow dowel to do it (the BRP). Sorry for all the acronyms btw. Saves time on my tiny ass 3.5 in keyboard.
T It either came like that, or took a breaker bar to do.
Or repeated impacts.
http://media.toolweb.com/datafeeds/250x250/2da4ea4e-16ad-4878-bc30-0ca074f42006.jpg
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