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No, not without modification. Most 9mm lower receivers have the ejector built into the receiver, as standard Glock and Colt compatible 9mm carriers have no ejector. The CMMG bolt has the ejector built into the bolt (similar to a .223 bolt), so it will not work with a lower that has the ejector.
I can confirm that this barrel/bolt kit WILL work with the Foxtrot Mike 9mm lowers if you just remove the ejector, I am using a FM-9B upper/lower glock set and it functions 100% using standard carbine spring and 3oz carbine buffer. I should note that my upper is the standard charger not the side charging model.
Yes, in fact a Foxtrot Mike's lower lower already has a mag stop milled into the magwell to prevent your magazine from interfering with the bolt. Some manufacturers use the ejector to limit magazine height. You only need to remove a little material from the top of the mag release to lower the magazine height in the magwell. I have almost a year and a half on my Foxtrot Mike's/CMMG build and it runs like a sewing machine. It only takes some basic mechanical skill to figure these things out. If that's not part of your skillset either have a gunsmith do this for you or buy a complete firearm.
Answer 2 and 3 are correct... especially 3 just built one of these in .45 acp it worked with the foxtrot mike lower but I removed the ejector from the lower, for obvious reasons, and took maybe a 16th off of the top of mag release on the inside of the lower so mags would drop free without sticking. The "expert answer" must not be an expert. No offense.
.03" is the number you want off the top of the mag release. If you don't go enough, it doesn't cycle smoothly and can be a pain to insert a mag on a closed bolt. Too much and it won't pick up the next round so it's a bit of a balancing act.
3-1/2 years and thousands of rounds later I can guarantee the info is solid. My machinist friend has modified at least a dozen Foxtrot Mike's mag releases to work with CMMG swaps.
Yes. Remove the ejector. I built 45acp using FTM lower. Runs perfect.
Yes. You can remove the ejector on the foxtrot mike. I used Foxtrot Mike lower for my 45acp build. It runs perfectly.