Mil spec push pins on lowers?

[dcnyli]

Looking to put a 300blk upper onto an existing cross machine tool lower I own, says it will drop into mil spec push pins... How can I tell if they are spaced properly?

 

[M25BeastShooter]

Its not the spacing its the diameter of the pins. Currently as I know everyone BESIDES Colt rifles are running "mil-spec" take down pins

 

[mallrat]

Are you having difficulty pushing the pins in? Seems to be some variance in tolerances, some "mil-spec" uppers fit "mil-spec" lowers fine, some bind, pretty much just have to trial fit. IMO.

 

[dcnyli]

I haven't ordered the upper yet, I was unsure of fit. Also I plan to build it as an SBR so need to be sure I go about this correctly/legally