Current BCM Upper Barrel Fit

[OldState]

I’m drawing up a precision DMR type build on paper And doing my research before I start buying. Been reading up on barrel fit and bedding. Looking up BCM receivers and they have this in their description:

“ Built to the correct Mil-Specs
(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.)”

Has anyone had experience with this? Does this negate the need for bedding? Thanks

[everready73]

I don't know if bedding would still be beneficial but I can confirm the 3 I have used soon had a very tight fit and needed heat to get the barrel in. I put the barrel in my freezer for one if them that was a little tighter than the others

[jsbhike]

3 for 3 on requiring heating also.

Just became aware this week White Oak claims to oversize their barrel extensions 0.001" versus others which has me curious how a BCM would interact with such an extension.

[Clint]

Yes, undersized bores or oversized extensions will generally require heat to to assemble.

This tight shrink fit is generally good from an accuracy standpoint and should eliminate the need for any bedding.

[GH41]

Yes, undersized bores or oversized extensions will generally require heat to to assemble.

This tight shrink fit is generally good from an accuracy standpoint and should eliminate the need for any bedding.

Clint, You seem to be well respected here.. What does one really gain by bedding the extension? Real world benefits for the guy shooting quality factory ammunition with a trigger safe enough for real world use. I understand it may be a psychological advantage if your that kind of guy. I know I wouldn't benefit from doing it but I am the guy happy to shoot 6 inch groups with green tips off of an improvised rest with a six pound rifle!!

[Clint]

It's hard to directly establish the gains from a good fit, but eliminating variables is always good for consistency.

Some sources claim 1/3 reduction in group size.

Dirt shooters won't appreciate the effort required to achieve a good fit.

Here is a great discussion on techniques for accurizing ARs.

https://www.m4carbine.net/showthread...-Accurizing-AR

Clint, You seem to be well respected here.. What does one really gain by bedding the extension? Real world benefits for the guy shooting quality factory ammunition with a trigger safe enough for real world use. I understand it may be a psychological advantage if your that kind of guy. I know I wouldn't benefit from doing it but I am the guy happy to shoot 6 inch groups with green tips off of an improvised rest with a six pound rifle!!

[OldState]

3 for 3 on requiring heating also.

Just became aware this week White Oak claims to oversize their barrel extensions 0.001" versus others which has me curious how a BCM would interact with such an extension.

Good to know. White Oak was a barrel I was considering.

If the BCM receivers are as tight as described I guess bedding or shimming would be pointless.

[SeriousStudent]

I have used a heat gun and fitted two of them with no issues. That is only a sample size of two, for what that is worth.

[ST911]

I’m drawing up a precision DMR type build on paper And doing my research before I start buying. Been reading up on barrel fit and bedding. Looking up BCM receivers and they have this in their description:

“ Built to the correct Mil-Specs
(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.)”

Has anyone had experience with this? Does this negate the need for bedding? Thanks

I've converted bunches of carry handle uppers to flat tops using the blem BCM stripped receivers. All were a tighter fit than whatever configuration was changed. I don't remember heating any, but some needed a little more oomph than others. They are very good receivers at a steal of a price, and I will continue to use them.

[OldState]

I've converted bunches of carry handle uppers to flat tops using the blem BCM stripped receivers. All were a tighter fit than whatever configuration was changed. I don't remember heating any, but some needed a little more oomph than others. They are very good receivers at a steal of a price, and I will continue to use them.

Good to hear