I have close to 2,000 rounds through my SBR’ed Ameetec lower. I was showing it to another officer recently and he noted that the stock was canted. Well, the staking had apparently come loose so I rethreaded it and lock-tited. Shortly after that I took it apart to clean and the buffer retaining pin went flying across the room. I reinstalled it and noted that the receiver extension was barely engaging it and that the end of the extension looked somewhat peened around the entire circumference. There was also no finish left on the receiver end of the extension.
I checked it against another Ameetec built lower that was purchased at the same time and this extension was finished and showed no signs of peening. It also engaged the buffer retaining pin very positively.
My question is has anyone experienced this before? Is it something that can be remedied aside from replacing the extension every 2,000 rounds?
Thanks for any insight,
Scott
Pic added, that thing is being held in there by a hair as you can see:
Because of manufacturing tolorances, I have seen receiver extensions on mix and match guns just barely engage the buffer retaining pin as you describe. When you try to turn it one more turn, it goes to far and bangs up against the retaining pin. My solution on one occasion was to use just a bit of sand paper to take off a hair of material around the bottom of the receiver extention so it did not interfear with the retaining pin. Once that is done, you will be good to go. If you are buying a new one, buy a quality unit from Colt, LMT, DD or BCM and it should not be an issue. If it is, just get out the sand paper and go slow.
Not normal at all. I would start buy purchasing a quality lower receiver extension and see if the issue persists. I HIGHLY RECOMMEND THAT YOU NOT USE LOC-TITE.
You may also want to consider a new end plate and castle nut. If the issue doesn’t get fixed then your lower is more than likely out of spec.
I appreciate the responses guys. What’s the reason to not use loc-tite? I’m not arguing, I’m just curious.
If I turn it one more time it engages the retaining pin just fine but then I can’t close the upper.
I really don’t want to hear this due the extra $200 invested in this lower. I do have another extension ordered although it’s another commercial one. Perhaps I’ll have to see how the new one runs and if it persists, get a mil-spec one to see if that alleviates the issue.
Imagine backing your castle nut off a little, then feeling some resistance. You give the castle nut a little more torque and notice that the receiver extension is actually rotating a couple of turns rather than the castle nut. But it’s ok right? The receiver endplate will just pop free and you’ll be golden, except loctite has frozen the endplate in place as well as the castle nut and you’ve been destroying the receiver extension threads as you back the receiver extension off without the endplate hanging free.
I’ve seen people do this with red and blue loctite, I’ve even done it myself when I was new to building lowers. Since I started staking the castle nut in place, I haven’t had any such issues and I’ve never had a RE work loose.
What is up with all the aluminum shavings and chunks?Ive never seen a mess like that.
I’d do as described by the others and buy a “known quality” RE,clean up the mess and do a proper install.Until that is done I would not mess with it or use it.
This was staked very well when I received it from Ameetec so I thought I was alright, that’s what baffled me when the other officer I was showing it to mentioned the canted stock, it had worked loose.
I’m sure some of the shavings are from the extension end rubbing against the retainer when I turned it in farther but the finish was gone and the edges were peened long before I did that.
If you look where the extension “engages” the retainer, you can see it’s slightly humped up there. You can feel that hump if you run your finger over it.
Alright, I’ll get it as squeaky as I can, install the new parts WITHOUT loc-tite and then stake it.
Don’t bother trying to save the tube this time when you consider how bad it would be to have it break the day you are using it not on a range (which hopefully never happens).
When you get the new tube for this gun (since its sbr’d i’m sure your keeping the lower regardless of perfect specs) thread it in and check the engagement of the buffer retainer to the tube. If the lower is a little “long” and you need to thread in one more turn you can take a scribe or even just a pencil to mark the tube where it blocks the upper from closing and make sure the buffer retainer pin isn’t wedged (this can be filed or dremeled for fit as well) and then TAKE THE TUBE BACK OUT TO DREMEL OR FILE FOR CLEARANCE. Then you just put a little black on the end of the tube so it looks right when your cleaning (it bothers some people I guess). Then it should fit fine.
You may want to check the alignment (centering) of your buffer retainer as well in relation to the bolt carrier to make sure something isn’t rubbing i’ve never seen that be a problem but stranger things have happened.
I received my parts from RRA today and got it back together. The extension threaded in to cover almost half of the retainer and the lower and upper closed together perfectly. Comparing the old and new extensions, the old one definitely had some material missing from the threaded end.
Now all that’s left is the staking.
I guess we’ll see how this one holds up and by that time it might be prudent to just get a mil-spec extension to hopefully remedy any goofy continuing problems.
Receiver extensions are one of the number of parts that I would never try to save any money on since they are an integral and critical part of the weapon.
I like VLTOR mil-spec RE’s which can be had for about $45 from most anywhere.
