Larue OBR in 6.5CM?

[KULT]

LaRue likely spec's an extension that is about 1000th or so looser than the bore of the receiver to allow for hand removal of the barrel and a carbine style ramp... 3-5 seconds with a torch would get the bat one to seat correctly but then that negates the ability to switch barrels. The tight fit does increase the potential for accuracy assuming that the receiver extension bore is faced correctly. I bet an armalite or dpms carbine extension would be a perfect fit. Using a carbine extension in an upper that doesn't have ramps cut is fine. You might get feeding issues if you use rifle one in an upper that has them cut because it creates a ledge. Either way doesn't matter now because the extension is on the new barrel and you can't swap it after the fact.

We measured all the 308 extensions and bolts in the shop for a project , need to see if I have the notes of what extensions had what spec. Most of them were within a 1000th of each other, but the uppers have a much greater spread depending on the maker and if they were billet or forged

Correct on both counts. The BAT is too tight to fit in the Larue receiver and there are deeper feed ramps on the Larue.

 

[George Mac]

The attraction of the 6.5 CM when compared to the .308 for me is - obviously - the 6.5 CM's higher velocity with a higher BC projectile. To go shorter on the barrel would negate the velocity advantage to some degree.

I will tell you that the rig shown above with 24" barrel, complete with suppressor, is a handful, no question about it. But, it seems to work quite well for its intended purpose, long range capability.
Something 16" like this .308 is much easier to maneuver:

I just got in a Krieger (AR10) 6.5 1/8 blank. My 6.5 creedmoor R700 has a 22.5" barrel and pushes the burger 140's at 2830. I was thinking to cut this new barrel for my tOBR and canabalize the field grade parts. I've read through your posts and wanted to know if there is anything that you would change in retrospect?

 

[George Mac]

Pulled the barrel nut off of the Field Grade barrel and got to work...
1. New Krieger at 27" will most likely cut it to 24" and see how it feels. It still balances nicely even this long.
2. Turned down and polished the Krieger barrel extension mic'ed it perfectly... Such a sweet fit.
3. Feed ramps are prefect
4. Assembly check. BO low profile gas block fits perfectly under the hand guard but may go with an adjustable.