Compatibility and setup notes from Foxtrot Mike Products in Boise, Idaho. For PDFs and how-to videos see manuals. For a broken gun see warranty.
Which magazines does Foxtrot Mike support?
Magpul and OEM Glock magazines only. Import magazines besides OEM Glock are unsupported. SGM magazines are not compatible.
Can I use aluminum-cased ammo?
No. Foxtrot Mike Products does not support aluminum-cased ammo. Blowback PCCs see a higher chamber pressure spike than a handgun. Aluminum-cased ammo in a blowback PCC is dangerous and voids the lifetime warranty on a Foxtrot Mike upper.
Will a Foxtrot Mike 9mm upper run on a Spikes Glock-style lower?
Not as a supported setup. Spikes LRBHO geometry has changed several times and needs the Foxtrot Mike upper cut to make room. The upper is cut to Colt mil-spec. Cutting it to fit a Spikes Glock-style lower voids the lifetime warranty on our PCC uppers. Removing the LRBHO on that lower does not void the warranty.
Do you support Stern magwell adapters?
No. Stern adapters need extra adjustment. We recommend Sylvan magwell adapters, which do not need modifications to work.
What is the handguard inner diameter?
1.3 inches.
What buffer and spring should I use with a 9mm upper?
A 6.5 oz buffer and a .308 / heavy carbine spring. A standard carbine spring is not the recommendation, including with our heavy 9mm buffer in a carbine tube.
Does the billet lower have last-round bolt hold open?
Yes.
How do I torque a barrel nut?
Hand-tighten the nut, slide the handguard over it, and see how far you must turn to align the holes. Tighten a little at a time with a 1 3/16″ or 30mm box wrench. Do not pass the next set of holes. When the holes align, Loctite the eight socket-head cap screws and snug them with an Allen wrench.
More assembly detail is in the quick-start guides.