I’m running the MBX mini. As long as the mag is cleaned and lubed with dry Teflon about every 400 rounds, it runs flawlessly. If you push the round count up towards 500 or more rounds, it starts to not work. It’s set up on an ETS mag.
Save yourself a headache down the road and just get the ramped barrel from Taccom. Tim is a super guy and stands behind his products. Go with his extreme bolt and then you’re GTG for the ramp.