AR 15 Receiver/ Barrel problem

[K.C.Dean]

I got everything to build an upper. Everything came from BCM. The barrel will only go into the receiver about 1/8 of an inch. I wanted to see if you guys could help? I would really appreciate any help or advice. Thanks!

I have my Grandson here and he wanted to do some cool faces.

 

[HT4]

Not uncommon. If it goes in at all (as your does), grease and a rubber mallet may be all that is needed. The barrel nut does the trick after you get it over halfway. I've also heard of the freezer/heat gun method, but never had to use it myself. Make sure everything you need (barrel nut, etc.) is in place before attempting, if that is needed.

Good luck.

 

[l730dc]

Use a floor jack and wedge it against something


disclaimer. . Do not actually do this

 

[Bountied]

I would use 800 grit paper on the barrel extension and then some antiseize, like switching the barrel on a 10/22. I'd be leary of using a rubber mallet on or near the crown to tap in the barrel. I've built three ARs and never had to bang the barrel in the upper receiver, sounds a little off.

 

[jsnider22]

If its a new BCM upper its because they now slightly undersize that part to allow for a tighter fit. I'd go the heat gun method it shouldn't take a whole lot to make it happen but when you do it make sure everything is in place if not pulling the barrel out will be a pain in the ass.

 

[HT4]

I would use 800 grit paper on the barrel extension and then some antiseize, like switching the barrel on a 10/22. I'd be leary of using a rubber mallet on or near the crown to tap in the barrel. I've built three ARs and never had to bang the barrel in the upper receiver, sounds a little off.

Always good to be leery about banging on the crown, but a rubber mallet will not hurt it... If I really bothers someone, they can use an old A2 flash hider, or something like that for protection.

If re-sizing is absolutely needed (and it may not be in this case), my rule of thumb is to always take material from the cheaper/easier to replace part... There are exceptions, of course, like if the cheaper part is also the serialized part. It's a matter of judgment. But in this case, the choice is between a $100 stripped upper and an approx. $300 barrel.

If the OP does something like this, be sure not to F-up the M-4 feed ramp alignment... it would be VERY easy to make a jam-o-matic gun by sanding in this vicinity. Also, definitely make sure not the remove any anodizing from the feed ramps. That is one of the few places on the AR where the extra surface hardness of anodizing is really mechanically useful.

 

[armed ferret]

 

[rseymorejr]

I would use 800 grit paper on the barrel extension and then some antiseize, like switching the barrel on a 10/22. I'd be leary of using a rubber mallet on or near the crown to tap in the barrel. I've built three ARs and never had to bang the barrel in the upper receiver, sounds a little off.

I wouldn't use anything with graphite in it. Graphite corrodes aluminum.

 

[DoubleTap007]

Can you get the barrel nut on ? If so, that will pull it in, obviously check for any obstructions, burrs, etc. A touch of lube will help as well.

 

[K.C.Dean]

Thanks for the help! Maybe I'll take it to a gun smith. I built one before but it was a Yankee Hill upper receiver and a BCM barrel and it slid right in. I am in no hurry. I will keep researching. I don't want to buy the stuff for lapping the receiver and or barrel. I was thinking about putting the barrel in the frig. then heat the receiver with a hair dryer use a little lithium grease and see if that will work.

 

[Bafflingbs]

I wouldn't use anything with graphite in it. Graphite corrodes aluminum.

Damn good info. I didn't know that. Thanks.

 

[armed ferret]

Thanks for the help! Maybe I'll take it to a gun smith. I built one before but it was a Yankee Hill upper receiver and a BCM barrel and it slid right in. I am in no hurry. I will keep researching. I don't want to buy the stuff for lapping the receiver and or barrel. I was thinking about putting the barrel in the frig. then heat the receiver with a hair dryer use a little lithium grease and see if that will work.

Standard wheel bearing grease (as long as there's no graphite) such as the kind used by many on this forum, including m'self, for AR-15 bolt carriers and bolts, will work fine. Stick the barrel in the freezer for a few hours, pull it out, lightly grease the extension, and you should be able to get it in far enough for the barrel nut to engage the upper receiver threads. That'll seat it the rest of the way.

If you still need help, and you're in SoMD (judging by your mention of the motocross track down there in your location I'm assuming that's the case) come by the AK build party that tc617 is being kind enough to host and I can bring my upper vise blocks and barrel nut wrench and get it assembled for ya there. 2 May, I do believe. Couple weeks away.

 

[K.C.Dean]

Standard wheel bearing grease (as long as there's no graphite) such as the kind used by many on this forum, including m'self, for AR-15 bolt carriers and bolts, will work fine. Stick the barrel in the freezer for a few hours, pull it out, lightly grease the extension, and you should be able to get it in far enough for the barrel nut to engage the upper receiver threads. That'll seat it the rest of the way.

If you still need help, and you're in SoMD (judging by your mention of the motocross track down there in your location I'm assuming that's the case) come by the AK build party that tc617 is being kind enough to host and I can bring my upper vise blocks and barrel nut wrench and get it assembled for ya there. 2 May, I do believe. Couple weeks away.

I really appreciate it AF! I would like to come by the AK build just to see how everything works. I'll even bring some refreshments. I'll check that thread out and see if it's okay.

 

[K.C.Dean]

I got the barrel mounted. I did what Armed Ferret suggested and put the barrel in the freezer then heated the receiver with a blow dryer put some white lithium grease on the barrel extension and the barrel slid right in. It went in so easy that it surprised me. Thanks for the info!!

 

[armed ferret]

It went in so easy that it surprised me.

 

[Russ D]

Pure Gold.

 

[precisionfire]

BCM purposely undersizes the receiver bore. You are supposed to heat it with a hair dryer till it is about as hot as it will get with a hair dryer (we use a torch here - very lightly). Aluminum expands quickly and the barrel can be slipped in with no issues. DONT use a hammer. A wood block or mallet works, but tap it lightly. Supposedly the tighter fit makes for more accuracy. Although most BCM barrels wont know the difference.

 

[armed ferret]

you don't need to heat it. just smack it on the crown with a 3-pound steel-face hammer. it'll be fine.

 

[BradMacc82]

you don't need to heat it. just smack it on the crown with a 3-pound steel-face hammer. it'll be fine.

But I only have a 5lbs steel-face hammer....

 

[armed ferret]