I have a quick question for yall.  

I have a Vltor upper which i think is made to be a little tighter than the rest.  I also have a Noveske barrel.  The issue is the barrel extension is about .003" larger than the upper.  

Does anyone see any issues with a "press fit" by heating one and cooling the other?  If i remember right i should heat the upper and cool the barrel right?  

Do any of you have any suggestions or similar experiences?  

Thanks for any help.  

One of the two is not in specs.
Measurements?
If put together in an interference fit as you suggest, it will not ever come apart, even iif you want to change one of the two parts in the future...

The upper should be something like 1.002"

Ok well here are some better numbers but they are still very close and not as far apart as i initailly measured.  I think Vltor may make theirs a little on the tight side for a tight fit on purpose though.  Or it could be a dull reamer if thats what they make the final pass with.    

Upper: .997
barrel ext: .998

I think being that close i could get them back apart reletivly easily considering how i put them together if i heat and cool them.  I wish those numbers were reversed though.    

A LMT Upper that i replaced with this one was 1.000".  Dont get me started on that upper.

You'll need to cool them both.

Nope.  If you cool them both the aluminum of the receiver will reduce in size at twice the rate as the steel of the barrel, making it impossible to fit them together....
With the size difference of .001 of he two, the reciever would have to be about 90°C higher than the barrel to get .001" clearance, which is iffy on inserting it, so a temperature differential of > 200°C would give you leeway to fit it together.
That said, you'd probably never be able to get it apart, as you you'd have to heat the receiver to take it off the barrel, as you would have to get it really hot
The barrel will cool the receiver off rapidly, causing the interference fit again...
The receiver is out of specs of 1.000 ±.002" (barely)
The bolt/carrier fit is good?

Something is definitely out of spec.  You have a 0.001" interference fit.  This is not acceptable.  Send the parts back for replacement.

Im going to try to give Vltor a call on tuesday and see what comes of it since the barrel fits in a couple other uppers i have.  I dont have any doubt that if the problem is on their end they will take care of it.  I just wasnt sure if it was how they were made or if i really had an issue.  

Thanks for the help.

The barrel is a Noveske 12.5".

Good post.  I have a Noveske barrel on order and tring to find an upper and I have been looking at the Vltor MUR.  This is making me think twice, I amy instead go with a Larue.

If you put the aluminum in the oven at 250 f. the barrel should slip right in. It is done all the time with blind bearing
races in aluminum housings. Same for removing it. The steel will not expand at anywhere near the rate of the aluminum. As far as it being ok to have an interference fit on the ar I don't know, but .001 is about right for most
applications where a "press" fit is desired.

Well fixit i decided to to try out what you said since it was close and the temp wasnt too hot.  I heated the oven to 250 degrees and left in in for maybe 3 min without preheating and tried it.  I quickly applied some high temp moly (no graphite) to the hole then literally dropped the barrel into place.  Most all of it was pushed out by the barrel ext. so i think just a very fine film may be on the parts.  It took zero effort on my part.  Since it slid in that easy i dont think ill have an issue removing it again if needed even considering im heating both metals.    

Ive released bearings that way in aluminum housings as well so i dont know why i didnt atleast try it earlier.  

All said and done i think im happier with it being a tighter fit for accuracy reasons.      

Thanks for the help.



Just to add i did let it cool then reheated it and the parts did come apart so no issues there.

I've assembled this combination before, it was tight, but I made it work, and the weapons shot very well.