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BoilerUp
7 May 2017, 09:00
Any experience building on a stripped BCM upper? I picked up a blem a year or so ago and finally got a barrel for it. The barrel extension won't fit in the receiver, which is apparently by design:


(Inside Diameter for barrel extension slightly undersized for a tighter fit to the barrel and a more accurate rifle. Please use a heat gun or hair dryer to warm up threaded bore of receiver if barrel extension is too tight.)

Source: https://www.bravocompanyusa.com/BCM-Upper-Receiver-Assembly-M4-Flat-Top-demo-p/flat%20top%20-upper%20-m4%20demo.htm

That means my lapping tool won't fit either and I'm a bit concerned that removing the barrel would be quite a pain (and BCM uppers have that reputation). I know that, eventually, I'll likely want to change out the barrel, so I'm trying to decide if I'll regret proceeding with this upper or if I should just pick up an Aero for $50.

GOST
7 May 2017, 10:01
I've had some BCM uppers and they were all very tight by design. I used a Scotch Brite pad on the contact surfaces, then chilled the barrel and heated up the upper. I put some Aeroshell on the contact surfaces also. They were tight enough that I would probably buy another receiver than try to beat the barrel out of it, if I were wanting to change the barrel.

Slippers
7 May 2017, 10:06
I had one that was extremely difficult to insert the barrel extension into. Tried heating it, freezing the barrel, lube, everything. Also tried a few different barrels to make sure it wasn't the extension. I sent it to BCM and they replaced it. The new one is similar to my three others; snug, but not difficult to install/remove barrels.

inthegame
10 May 2017, 13:03
If your already thinking of replacing it, then your looking at tons of round down the range. Go with the bcm. It's going to hold tight as needed

BoilerUp
10 May 2017, 19:50
If your already thinking of replacing it, then your looking at tons of round down the range. Go with the bcm. It's going to hold tight as needed

I have no expectations that I'll wear out a melonite barrel. I just like to tinker and am always messing with my toys so expect at some point I'll want to pop the barrel. For my current project, I've decided to go with a different (matching) upper so I'll likely save the BCM for another project.

docsherm
10 May 2017, 20:53
I have also had experience with this issue and it caused the barrel to be off to the point that it would not shoot straight. It was a DD barrel and it was sent back to DD for inspection and there was no issue. They replaced the barrel and it still was not possible to zero it. Upper receiver was swapped out and there was no issue. I avoid BCM uppers for that reason.

SINNER
11 May 2017, 04:02
I wish every upper I purchased had this issue. Easy to remove metal but impossible to replace it.