Using my new Bushy Dissy upper I had to exert more force than necessary to get the magazine to click in place. The mag was not completely loaded.
This same mag did not require the same amount of force to engage when loaded into a different upper( also from Bushmaster ). It definitely seems like tolerances are juuuuuuust a bit different somewhere.
Any suggestions for making a better fit? Currently this mag / upper relationship would be terrible during a stressful situation where suddenly I would have to wrestle with the damn thing to get it to load.