Ar15 barrel fit question

[Grand]

I picked up a Larue Upper and Larue PredatAr 5.56 barrel. The Upper barrel opening measures .995" and the barrel extension measured 1.02" So, I've got .007" and the barrel won't fit. Measured my Noveske barrel and its an even 1.00" but still too tight. I know some guys heat the upper in the oven to get additional clearance, but I don't think I can overcome .007" with heat. Anyone have experience with this issue. I'm am thinking the upper is the issue. Thoughts?

 

[Weber]

Put the barrel in the freezer, heat the receiver it will slide in.

If you can get it started, lube and barrel nut should get it in.

 

[conksarmy]

To the op:
I'm with you. I dont think heat is your answer. I have built several and have never had a barrel/reciever that wouldnt slide together with ease. I think one or the other is out of spec or you have a proprietary product spec issue. Since they are both Larue i would call and ask what they ought to be and make sure both are indeed compatable. I dont feel like taking an upper apart or i would measure mil-spec to give you a frame of reference. I guess if they dont have your answer, holler and i'll pull it apart to see. Good luck man.

 

[bustin]

I picked up a Larue Upper and Larue PredatAr 5.56 barrel. The Upper barrel opening measures .995" and the barrel extension measured 1.02" So, I've got .007" and the barrel won't fit. Measured my Noveske barrel and its an even 1.00" but still too tight. I know some guys heat the upper in the oven to get additional clearance, but I don't think I can overcome .007" with heat. Anyone have experience with this issue. I'm am thinking the upper is the issue. Thoughts?

The spec on the extension is .998. Tapping them in is ok when there is a few thou interference fit but not as much as you are stating. A tight fit means a rigid connection and concentric on the bore of the receiver...tight is good. In your case if the extension is 1.002" I would return it and ask for one that meets spec.

 

[elephantrider]

2nd, or 3rd that heating and freezing are not the solution here. The barrel extension should go in without any tools required. At worst it should require a little lube and some light raps from a small hammer nylon tipped gunsmithing. This problem seems to crop up most with billet uppers from various manufacturers. For some reason they tend to machine them on the tighter end, or just outside of, the tolerance specifications. One of the many reasons I avoid billet anything. See if you can get Larue to sort this out for you.

 

[Thumper580]

You might get it together with hot and cold, BUT more than likely it will never come apart! Agree with above posts, something is off spec. Don't force it....

 

[CK_32]

I had the same issue with my mega barrel into my JD matching receivers.

I tried the freezer and heater method didn't help sh** just had to he man it into the receiver. MAKE SURE YOU PUT LITHIUM GREASE!

 

[Grand]

Measured my Vltor upper and is measures .995" as well. Starting to sound like the Extension is the issue.

 

[Little gator]

I haven't miked any of my builds ( I want to preface this with that)

4 of my 5 builds slid in snugly. My 3rd build was a yhm barrel and yhm upper, you would think " hey this will fit great!" No. Stopped about 1/6th inch from fully seated. I took it to the local ar15 expert. (He was a police armorer master gun smith and had some other papers on his wall along with 40+ years XP) he told me,

Get a small mallet/dead blow and use "30%" power to knock it in. Make sure you anti seize it. And apart from a, being a bi$@ch to get out or b, having to buy a new upper when you replace the barrel in 10,000 rounds. There are no adverse affects.

I went ahead and pounded her in. I've had no problems. Granted 10k down the road I'm be cussing my self out but.....that's a long way off.