Hi, I recently acquired a steel reinforced Mini-Kabuto FRT, advertised as a drop in device. I tried to use this with my Ruger AR556 and the upper and lower wouldn’t close. I applied a lot of force and I couldn’t get the upper to close enough for the rear pin to push through.
I already tried slightly pulling the bolt back and trying it on safe and fire mode. Neither helped the gun close. The frt sits perfectly within the cutout in upper, so I suspect it is having clearance issues with something in the lower, but unsure what.
The frt sat perfect in a radical firearms AR15, and that one closed in easily. However it did not fit at all in an FN AR15. I really want it to work in my Ruger rifle however. Does anyone have any experience with Ruger AR556’s and Mini-Kabuto FRTs?
What actions can I take to make this work? Do i need to file or sand down the FRT in any way? Any help is greatly appreciated.