I've seen plenty of videos about installing the barrel into the upper and I have a torque wrench, so I thought this would be easy. I have a barrel from AR15 Performance and an upper from Rainier. I slid the barrel into the upper about half-way and started feeling some resistance. I assumed I has it at an angle so I gave it a good push. Now the pin is sitting just outside the notch and the barrel won't budge. I mean this thing is really stuck.

I'm worried if I force it in with a heavy hammer over a 2x4 it will shear the receiver or be eternally wed or both (if none of the above have already happened). I'd like to get the problem resolved where both parts are functioning and fitting normally as they should instead of putting it off until I have to rebarrel in a year and both parts are no longer warrantied (assuming they are currently).

I sprayed some WD40 on it overnight without any luck. I have no idea what to do at this point. Even if I find some way to pull the two pieces apart, one of them would need to be replaced. I don't feel I should have to pay a smith when this is clearly an issue of a manufacturing defect. I have no idea which part is over or under the maximum tolerances, but clearly either the barrel (melonited barrel extension could be too thick from coating?) or the receiver is not right.

Has anyone else had an issue with an ARP barrel or Rainier upper? Any suggestions?

UPDATE: I received a reply from ARP saying "Tap it in without damaging the crown". I grabbed my rubber mallet and gave it several taps. It probably took close to 100 good medium blows to get the thing all the way in. Still, when it comes time to rebarrel in a year or two I'm worried this will be a real bitch, especially since I didn't use any antiseize when planning to be doing a simple test fit. Any suggestions are still greatly appreciated for how to disassemble. Thanks!

I was hoping to have the receiver painted; so, disassembly is fairly important to me, especially after spending so much money on this build. I'll try a heat gun and post my results. Thanks.

Wooden dowell through the upper to the feed lip portion of your barrel. Knock that sucker out. Wood will give before the metal does.

Had the same issue with a SS barrel from BCM in a LaRue upper. Had to use a dead blow to get the barrel fully seated into the upper during assembly.

this to get it back out and then make sure both parts are really clean and add some moly grease to em before refitting

Don't use anything with graphite in it. The graphite will hasten a reaction (galvanic response perhaps?) between the two dissimalar metals in the barrel (steel) and the upper receiver (aluminum). Do a little more reading and research before you put it together. It's not hard but do it right....<><....:)

@Killroy:
First build. I planned on sliding it in, having it look nice, and sliding it back out, but it got stuck without any lube [that's what she said]. LOL...sorry
I wasn't assembling for function and was under the impression the grease, or whatever it is, simply prevents corrosion for long-term assembly. Live and learn.




I've probably read 5 lenghty posts at this point and ALL of them are one opinion after another without any definative answers. It seems like even though everyone is touting their own choices, none of them have actually experienced problems with any product and are all simply speculating about issues.

I had one like that. I gave it about 5 good whacks with the rubber mallet to get it in, and I whacked it on the FSB to get if back off. It really isn't that big of a deal and there is no need to start putting all kinds of crap on it that is not normally used to begin with.

Trooper;
One of the posts earlier suggested that you use a heat gun & apply heat to the upper receiver.
That was good advice. Aluminum expands more than stainless steel when it it is heated. Aluminum also
conducts heat far better than stainless steel so the heat gun will heat up the upper a lot faster than the barrel.
You can try putting the barrel & receiver in your refrigerator for a couple of hours, then apply
the heat. Your barrel should come out fairly easily then.

Roger