Barrel extension too tight in upper - Page 1

AR-15 » Build It Yourself

AR Sponsor:

[ARCHIVED THREAD] - Barrel extension too tight in upper

Posted: 10/9/2017 1:45:33 PM EDT

Putting together a new gun for a friend. He purchased a stripped blem upper from BCM. Barrel extension is way too tight to insert into upper receiver. I tried a few spare BCM uppers I have and the barrel slides in easily enough. Should I lightly sand the inside of the receiver until the barrel fits?

This is the first time out of all my builds that I have experienced this and unsure of how to proceed.

Posted: 10/9/2017 1:50:44 PM EDT

[#1]

Place the barrel and extension in the freezer overnight and see if you can get it to slide in before you commit to removing any material off of the upper.

Hope this helps.

Posted: 10/9/2017 1:54:58 PM EDT

[#2]

Heat the nose of the receiver with a heat gun, it'll go in then. No need to freeze the barrel usually.

Eta: I would not sand the receiver.

Posted: 10/9/2017 1:59:17 PM EDT

[#3]

No sanding.

Use a propane torch to heat the receiver.

BCM receivers are usually really tight. that's a good thing in my book

Posted: 10/9/2017 2:47:53 PM EDT

[#4]

Just heat the receiver where the extension fits into and try, if it don't go still then heat the receiver after you have put the barrel in the freezer for a while, we do that all the time to install press on bearings in rear ends in trucks.. But heating the receiver should be enough to enlarge to tap the barrel home.

Posted: 10/9/2017 3:04:53 PM EDT

[#5]

Heated it and went right in just like it's supposed to work. First time I've ever had to use heat or freezing to get a barrel to fit on an AR. Even with multiple 10/22s.

Posted: 10/9/2017 3:18:47 PM EDT

[#6]

Quote History

Quoted:
Heated it and went right in just like it's supposed to work. First time I've ever had to use heat or freezing to get a barrel to fit on an AR. Even with multiple 10/22s.

View Quote

Glad you got it, it is amazing how tight a tolerance some of those receivers are milled to, but with aluminum as well as steel, heat or freeze usually does the trick. Normally what it is, is the finish on the receiver tightened it up enough to make it difficult.

Posted: 10/9/2017 11:40:11 PM EDT

[#7]

The upper I used in my last build was a BCM blem upper and like yours it was tight. I used a heat gun to warm it up and the barrel slid right in. I like how tight these uppers fit and will be using them I’m my builds from now on. Also used my lapping tool to make sure the face was square (may or may not do anything but figured it wouldn’t hurt while I’m there).

Posted: 10/9/2017 11:46:24 PM EDT

[#8]

Quote History

Quoted:
Heat the nose of the receiver with a heat gun, it'll go in then. No need to freeze the barrel usually.

Eta: I would not sand the receiver.

View Quote

This. Don't sand it. If you have to, freeze barrel and heat receiver threads. This interference fit is actually a good thing, IMO.

ETA: Saw you got it. Good going.

Posted: 10/11/2017 5:49:23 PM EDT

[#9]

BCM uppers are tight fit and they state this in the item description.

Posted: 10/11/2017 6:01:50 PM EDT

[#10]

I had a POF upper and a BA barrel that had this issue. It was like a square peg and round hole. Threw the receiver in the freezer for a few hours and it almost fit. Threw it in the freezer again for a few more hours and took a torch to the barrel extension and it fit perfectly. Made some cool sizzling noises for a minute and I'm not looking forward to ever taking it out.

Posted: 10/11/2017 6:09:39 PM EDT

[#11]

Quote History

Quoted:
I had a POF upper and a BA barrel that had this issue. It was like a square peg and round hole. Threw the receiver in the freezer for a few hours and it almost fit. Threw it in the freezer again for a few more hours and took a torch to the barrel extension and it fit perfectly. Made some cool sizzling noises for a minute and I'm not looking forward to ever taking it out.

View Quote

Isn't that backward?

Posted: 10/11/2017 6:15:18 PM EDT

[#12]

Quote History

Quoted:
I had a POF upper and a BA barrel that had this issue. It was like a square peg and round hole. Threw the receiver in the freezer for a few hours and it almost fit. Threw it in the freezer again for a few more hours and took a torch to the barrel extension and it fit perfectly. Made some cool sizzling noises for a minute and I'm not looking forward to ever taking it out.

View Quote

Given how cheap an upper can be, just treat this barrel and upper as a unit and if you want to rebarrel this rifle, just swap out the upper with barrel and never have to worry about pulling that tight bastard out of there again.

Posted: 10/11/2017 6:27:05 PM EDT

[#13]

Quote History

Quoted:

Isn't that backward?

View Quote

Yup it is, heat the receiver and freeze the barrel, heating the receiver expands it, freezing the receiver shrinks it!

Posted: 10/11/2017 8:15:10 PM EDT

[#14]

Quote History

Quoted:
I had a POF upper and a BA barrel that had this issue. It was like a square peg and round hole. Threw the receiver in the freezer for a few hours and it almost fit. Threw it in the freezer again for a few more hours and took a torch to the barrel extension and it fit perfectly. Made some cool sizzling noises for a minute and I'm not looking forward to ever taking it out.

View Quote

Wat?

Posted: 10/11/2017 8:25:08 PM EDT

[#15]

Quote History

Quoted:
Heated it and went right in just like it's supposed to work. First time I've ever had to use heat or freezing to get a barrel to fit on an AR. Even with multiple 10/22s.

View Quote

Theres fewer customer service calls if everything just slips together.

Posted: 10/11/2017 8:26:36 PM EDT

[#16]

Quote History

Quoted:

Wat?

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
I had a POF upper and a BA barrel that had this issue. It was like a square peg and round hole. Threw the receiver in the freezer for a few hours and it almost fit. Threw it in the freezer again for a few more hours and took a torch to the barrel extension and it fit perfectly. Made some cool sizzling noises for a minute and I'm not looking forward to ever taking it out.

Wat?

The lord looks out for the clueless.

Posted: 10/11/2017 8:46:33 PM EDT

[#17]

Quote History

Quoted:
The lord looks out for the clueless.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
I had a POF upper and a BA barrel that had this issue. It was like a square peg and round hole. Threw the receiver in the freezer for a few hours and it almost fit. Threw it in the freezer again for a few more hours and took a torch to the barrel extension and it fit perfectly. Made some cool sizzling noises for a minute and I'm not looking forward to ever taking it out.

Wat?

The lord looks out for the clueless.

I guess.

Posted: 10/11/2017 10:27:50 PM EDT

[#18]

Hahahaha. Just re-read what I said, yeah... I totally put that shit backwards. Mostly cause i remember trying to put the barrel in the freezer with all the damn food was a pain. Talk about

on that reply. Opps. Haha

Posted: 10/12/2017 10:49:20 AM EDT

[#19]

Torches and freezes are the wrong tools. One induces way too much highly localized heat and the other moisture in the form of condensation.

Warm the upper by use of a heat gun or a oven.

Posted: 10/12/2017 1:01:52 PM EDT

[#20]

Quote History

Quoted:
Torches and freezes are the wrong tools. One induces way too much highly localized heat and the other moisture in the form of condensation.

Warm the upper by use of a heat gun or a oven.

View Quote

Well all I can is there is a hell of a lot of us that have been using the torch and freezer method for a long time now. We even did it this way when I was in the service working in the Armory.

Posted: 10/12/2017 1:05:48 PM EDT

[#21]

I would be willing to pay extra for this kind of fit.

Posted: 10/12/2017 2:53:01 PM EDT

[#22]

Quote History

Quoted:
I would be willing to pay extra for this kind of fit.

View Quote

Most BCM receivers are this way.

Posted: 10/12/2017 3:34:28 PM EDT

[#23]

Quote History

Quoted:
Torches and freezes are the wrong tools. One induces way too much highly localized heat and the other moisture in the form of condensation.

Warm the upper by use of a heat gun or a oven.

View Quote

And yet it's been done a million times with no ill effects.

[ARCHIVED THREAD] - Barrel extension too tight in upper

AR-15 » Build It Yourself

AR Sponsor:

Warning

Confirm Action

About AR15.COM

Stay Connected

Newsletter

Contact Us