Do any of you see a problem with this barrel extension upper receiver fitment?



For comparison to another one of my uppers that uses the same brand and line of barrel as well as same brand upper receiver:

My LMT just like this too.

It won't feed reliably. Goes a couple of rounds then jams by either ramming a bullet back into it's casing or just ramming the bullet into that little gap between the receiver and extension, gouging the bulltet.


you can see where the receiver extension dug into the bullet.

Anyway, I clear the jam and it does it again.  You can see the copper build up on the lip.  So, I contacted the manufacturer. They proceed to tell me it is not out of spec and that it should feed with no problem.  I email a picture and they say OK, return it to us.  They proceed to wait nearly a month before they give it to their gun smith. He runs a magazine through it and deems that it is fine with no feeding issues.  Then this company proceeds to tell me that the out of spec receiver is not an issue but they are willing to go "half way" with me to replace the barrel extension.  I have used the same lower different uppers with no problem and 3 types of magazines.  Ammo I was using was PVRI Partisan 75 grn OTBT which has run hundred percent out of my other guns.  MY questions are; Am I crazy and this is not the extension, receiver issue.  Is this something that needs to be broken in?  Or is the manufacture bs'ing me on this.  I don't intend on putting this manufacturer on blast until I try the upper out again when it is returned to me.

looks like rifle extension with m4 upper receiver.

eta:looking at it again. it appears the ramps in the receiver are cut deeper/lower than your example on the left side of your side by side photo. so it kind of looks like it's the receiver to me. but, it wouldn't be too difficult to blend with a dremel or file.

So do you think a new upper receiver would solve the issue instead of a new barrel?  Compared to the picture you provided it looks like an M4 extension.

I think so....

are you able to swap barrels between those two receivers?
if the cuts in the extension from the picture on the right line up with the cuts on the receiver on the left. then, I would say a new receiver would fix it.
can you measure the distance from the bottom of the cuts in the receiver to the bottom edge of the receiver and compare them to the other one.
they look different. but, it may just be the angle of the photo.

I have another receiver that I can try swapping it with.  The other one pictured is my spr and I just got it all zeroed. I don't want to mess with it.  When the upper comes back to me, I will look at it.  I remember looking at the extension before I sent it back and feeling like the cuts weren't finished compared to the other barrel.

A dremel and a tapered chain-saw sharpening stone and you can blend them together in no time, but if you have a different upper it's worth checking fit there first.  I had an issue with a 300BO upper I build getting the tips of the bullets lodged just before meeting the ramps on either side.  Used that stone and opened them up less than 1/16" and now it runs like a sewing machine.

Good idea I may have to try that.  I didn't build this one.  Apparently the manufacturer used magic bullets that don't jam and does not think this is an issue.  Did you blend them while they were still together or did you unmount the barrel?

First I think I am going to disassemble the upper when I get it back and see how the barrel looks in another upper.  If it is the same, then I am going to move on to my next option.  There is a 90 day 100% money back guarantee and I am within that window.  Since they refused to fix this error, I am going to get a refund then go buy a Noveske barrel direct and never give this company any of my money again.

Really need them to be together to do a proper blend.  I have the cable-wand whatever you want to call it extension to my dremel and it was really easy to get to it all without taking the upper apart.  Just pulled it off the lower, went to work, sprayed it out with carb cleaner and blew it out with air then relubed everything.  Was quite easy.

Figured I'd add before and after pics...

Before:

And after:

Now all of the sudden they called me back and they will now replace the barrel extension so I won't have to file down anything or replace the barrel.