The left three cases were fired from a LaRue PredatAR with XTRANs chamber. The rightmost case came from a standard chamber.
XTRAN chamber left a sprial of carbon on the case. There is no felt damage to the case. This spiral of carbon could be wiped off with finger.
I purchased a used Magpul CTR stock with LaRue RISR and POD installed. It was interesting to try out the LaRue Reciprocating Inline Stock Riser (RISR) on an AR15. The RISR is made to give a higher cheekweld on rifles like the LaRue .308 OBR and accommodate the charging handle on the AR series of rifles.
I tried the RISR on a Colt 6920 first. I found the RISR to be high enough that I could not use the standard iron sights on the 6920. When I tried another upper with a NightForce 2.5-10×24 in a LT135 high mount. Even with the scope mounted higher then normal, I found the taller checkweld that the RISR gave made looking through the scope awkward.
Using the RISR gave a little more resistance then charging a normal AR15. Having an extended charging handle lever would help when using the RISR.
The RISR may be an excellent choice for high mounted optics on the higher rail of a .308 AR. However for me, the RISR just gets in my way on AR15s. I have already removed the RISR from my rifle and will be sending it to Shawn so he can try it out.