Tight BCM upper or loose Vltor MUR?

[opngrnd]

Alright, gents and ladies...I could use some advice from you human benchrests.

I have everything needed to build a precision upper(build parts listed below), but I'm facing a strange choice. I have a new BCM4 upper receiver and a new Vltor MUR, and a choice to make between the two.

1- The BCM4 has to be pushed on by hand, but isn't so tight as to need a rubber mallet introduced. Definitely doesn't just slide on, though.

2- The Vltor MUR slides on with a hint of wobble, though not a terrible amount. But the wobble is definitely there.

Which upper receiver would you use? (And if you could, please explain why.)

Parts list:
-BCM Comp
-Accu-Washer system
-Sionics 18" barrel (new version)
-Sionics gas block and gas tube
-Sionics 15" rail
-BCM BCG
-BCM Ambi Charging Handle
-BCM4 upper receiver (unused, but had on hand)
-VLTOR MUR-1A (bought for the build)

[opngrnd]

My two cents and thoughts: I bought the MUR specifically for the build because of its prevalence in being used for accuracy builds, thicker construction, etc. I had the BCM sitting around because I got a really good deal on it. Generally speaking, I would have thought the thick walled construction of the MUR would be an advantage over the standard construction of the BCM. I also understand that when you install a barrel nut it crushes the extension to the barrel, so it might be a moot point. But at this point I don't know where the advantages of one start to outweigh the other. Nor do I know when one has the advantage over the other when all things are not equal in regards to Barrel extension fit. So I'm hoping that the combined experience of the group leads to an obvious choice, given that there are a lot of uppers that have been built between the lot of us.

I have only built three precision uppers. All used the BCM4 upper receivers and the original 18" Sionics barrel, and all three shoot down to around 1.25 MOA using quality reloads not developed specific to the individual rifle.

[gunnerblue]

I'd use the MUR, especially if planning shoot suppressed. The added stiffness for a heavier barrel and can(?) is only a benefit. I admit to ignorance in regards to how much the barrel nut installation crushes the receiver threads.

[Fatorangecat]

I built an upper with a WOA barrel and Vltor MUR. I had the same concerns, my barrel to upper fit was way looser than I wanted. I torqued it down with a Geissele rail and it shoots awesome. My last range trip I had two 5 shot groups at 100 yards that measured less than .7 moa. I don't think a super tight fit is as critical as the internet would have you believe. In my experience accuracy is for the most part in the quality of the barrel.

[OrbitalE]

I built an upper with a WOA barrel and Vltor MUR. I had the same concerns, my barrel to upper fit was way looser than I wanted. I torqued it down with a Geissele rail and it shoots awesome. My last range trip I had two 5 shot groups at 100 yards that measured less than .7 moa. I don't think a super tight fit is as critical as the internet would have you believe. In my experience accuracy is for the most part in the quality of the barrel.

I have shot similar groups with a VLTOR MUR, Larue barrel, and Geissele rail. Wouldn't say the MUR wobbled, but it was nothing like a BCM.

[opngrnd]

Wobble is probably a bit of an overstatement, and is in comparison to needing to tap the barrel extension into the BCM4 upper receiver. I'll stay the course and use the MUR. Thanks for all the input.