A few months back I decided I wanted an ultra accuracy AR15 build so that I could really practice getting my shooting form and reloading down to a very high level and to get a baseline as to how good a shooter I could be (if I can’t occasionally shoot this ultra build to around 1/2 MOA I need to be flogged).

With that in mind, I did my research and decided on a 20” 1:7.7 twist, 4 groove Bartlein barrel worked up by Compass Lake Engineering. I had it built with their CLE chamber, rifle length gas setup, and the muzzle threaded 5/8” instead of the typical 1/2”. I also had them build it their SDM-R profile which includes 12 deep flutes under the handguard for a little bling and to shed a little weight.

As for the build, I selected the following components:
VLTOR MUR upper
SOLGW M89 15” handguard
Riflespeed adjustable gas system
Expo Arms chromed BCG (bolt sent to CLE for head spacing)

I finally got all the components in and started the build tonight. I used a Brownells lapping tool to lap the face of the upper (it was basically perfect from the factory and was probably the truest one I’ve done so far). I got the barrel installed into the upper using green loctite so it will be super snug, as this upper had a larger bore ID than other MURs I’ve used in the past, and was not a thermal fit. If I had some stainless shim stock, I’d have used it.

Before installing the barrel, I got some nice borescope pictures and everything looked great as far as I could tell. Here are pictures of the progress so far..

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Moar pix….
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Nice looking build.  Looking forward to a range report.

Looks damn nice. I have to ask,  but what caliber is it? Chamber? I assume it is 223, but I’m not sure.

223 with the CLE match chamber!

I'd be curious to hear what your headspace measurement is for that barrel.  I bought a Douglas barrel from CLE with their match chamber back in 2015 or so.  I've always thought the HS on my barrel was a bit on the short side.  Most factory ammo I've tried won't chamber, and the reloads for my other AR's won't either.  That being said, it shoots really well, as you would expect from CLE.

Do you have CLE do the head spacing on one of your bolts?

Are you mixing up headspace and freebore? I.e, if you seat the bullets shorter, do they chamber? The CLE chamber has a shorter freebore (~40 thou iirc) than a 223wylde chamber. So if you worked up a load for a bullet in a Wylde chamber, you may be jamming it into the lands in a CLE chamber if using the same seating depth. If loading closer to mag length, you’ll probably see an issue more with 52-69gr bullets due to the ogive position in relation to overall length. 77’s at mag length shouldn’t jam with either chamber.

I think in a previous thread you mentioned brass at 1.454” BTS chambering fine. Most factory ammo will be in the 1.451-1.453” range using the “A” insert with the Hornady gauge, which is why I’m thinking it’s the bullet seating depth causing your issue.

You may be right.  Looking back at my notes in resizing the brass to 1.453 according to the "A" insert.   69gr SMK's I was seating to 2.250" and 73gr ELD-M at 2.255".

Went and did the first sight in & zero session with this rifle today. It ran perfect once I got the riflespeed gas system adjusted properly.

Shot this nifty little 5 or 6 shot group with my 69 SMK + XBR 8202 “reference” load… lol… I think she has potential… (1” between the blue and black lines)

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Excellent shooting!