I'm trying to complete a SR-25/M-110 clone build but my state has banned all SR series rifles. I'm new to the LR .308/AR-10 platform rifles and I'm in the process of putting together a Tactical Machining .308 (DPMS platform) but I'm not super stoked about the options I have for upper receivers and free float systems. My question is will a KAC SR-25 rail and barrel nut work with DPMS upper receiver threads and barrel extensions? If not what other options would I have other than trying to get a lower that is SR-25 upper compatible or having a crazy super custom upper built? Thanks in advance for your help.
First, the rail type won't have anything to do with the barrel extension - don't sweat that in any configuration; the barrel extension has to be compatible with the bolt, though.
I highly doubt the KAC rail for the SR-25 will mount to the DPMS upper - but I've never removed or installed a KAC SR-25/M110 rail on anything before.
The basic design of the M110 is an Armalite pattern, with the exception of the mag style (DPMS) that the lower takes. The Armalite AR-10 and DPMS LR-308 upper receiver threading is different, and I'm betting the KAC rifles use the Armalite threading pattern, and not the DPMS. Additionally, Armalite and DPMS stock barrel nut outer dimensions are different, so you wouldn't be able to use a DPMS barrel nut and make that rail fit your gun.
I was shooting for a smiliar look on my DPMS rifle, and ended up using a Troy MRF-308 rail - that was as close as I could get. That rail comes with it's own barrel nut that is basically an Armalite nut on the outside, but threaded for the DPMS upper receiver. Getting that particular barrel nut (the Troy) to work won't even be a guarantee, unless you know for sure that the KAC M110 rail uses a stock Armalite barrel nut.
Hope that helps.
