As I understand it, 223 ar15s won’t cycle with any subsonic 223 ammo that one can obtain without a permit from the energy department (:) ). Given the limits of a 1-7 twist, the stuff we can handload is generally limited to 70 grains which just does not generate sufficient pressures to cycle an ar15 when kept in the 1000fps range.
However, I was just wandering through the brownell’s web site and noted that they had a titanium bolt carrier that “Requires substantially less gas pressure than standard bolt, so an adjustable gas block is recommended [when usign conventional 223 ammo]" This got me thinking that if one were to combine a lightweight bolt carrier, light weight buffer and bigger gas port plus adjustable gas block, one might be able to get an ar15 to cycle with subsonics. Of course, there would still be the problem of getting the same gun to work with conventional supersonic ammo without having to swap out a larger number of parts, but one problem at a time, and the brownells description seemed to indicate that the piece could cycle with this carrier with a gas block turned way down.
Anyone tried rebuilding an ar15 to cycle with available 223 subsonics?