Larue OBR 7.62 convert from PRS to Carbine tube

[USMCEODguy]

I have a 16" obr 7.62 that came with a prs stock. It has the carbine length (red) buffer spring with the H2 buffer and spacer for use in the A2 buffer tube. I have converted it (leaving out the spacer) to a carbine and have a mil-spec AR-15 tube that I put on. Larue said it should be fine... I took it to the range zeroed it, then moved into some drills. That's when it began to fail to feed. After looking into it, I noticed that the BCG would not lock back unless forced unnaturally. I've looked into multiple forums and haven't found a solid answer. Do I need a different buffer/ buffer spring or buffer tube? If I need another tube, will it support the mil-spec LMT stock that I have grown fond of?

Also, I called larue up on this and they said that the tubes they were using, measure 7 11/16th internal length. Not a mil-spec AR-15 tube obviously. I see OBRs out there with LMT SOPMOD stocks which only come in mil-spec dimensions so I need a AR-10 guru to help me out Someone has to have a solid answer out there for me.

[unforgiven]

Welcome from Indiana brother and THANK YOU for you'r service.Problems with a La Rue are not common.In fact it's the first I have read of.One of the guys will be along with some useful info.Did it work with the PRS without problems???

[USMCEODguy]

Thank you.

It works fluidly with the PRS. I'm just looking for more of a battle rifle setup, I have a few M40 builds in 20" and 24", as well as a 10" 5.56 AR. So my goal was to have a good medium range rifle with the TA648-308H ACOG glass on top. I know it'll get there eventually, but with me being the first person ever to have a problem with the larue I'm stressing just a tad!

[edgecrusher]

It's the tube that is ruining your day. Also I would change out the buffer and spring for proper 308ar parts from Clint at Heavybuffers.com. I run his heavy stuff on all my ar's, big and small, including my OBR. You will decrease recoil and follow up shots will be much faster, and yes, you can keep the SOPMOD. 

 

 

Here's a reference chart from his site, and you can see the tube is definitely off.

http://heavybuffers.com/reference.html

[USMCEODguy]

Thanks edge. One more question. What tube is the right one? Everywhere I am looking the only demensions sites give are Dia.

[USMCEODguy]

Think I'm getting the vltor re-10/a5sr. Mil-spec Dia. Extended length. Thanks for the help.