There are two different types of 9mm bolt carriers out there - ramped and unramped - and three different types of hammers.
CMMG, Spike's make a ramped 9mm bolt carrier which allows you to use a "DPMS" standard AR hammer - which will work for 9mm ramped and 5.56mm bolt carriers.
Rock River Arms and older Colt 9mm uppers uses the older style non-ramped 9mm bolt carrier which requires you to use a specific 9mm hammer, will not work with a 9mm ramped bolt carrier and does not work well with 5.56mm bolt carriers.
If you have an older style non-DPMS notched 5.56mm AR hammer - DO NOT USE THIS HAMMER WITH A 9MM UPPER - the notch on the hammer will bind to the bolt carrier causing the bolt carrier to lock up.
Other than this - Spike's and Hanh make really nice 9mm mag well which are compatible with "modified" 9mm Uzi magazine.
9mm ARs operate via blowback - so no need for a gas tube.
You can use a standard AR buffer, but most people recommend a heavier 9mm buffer for 9mm ARs to slow down the cycle rate and allow for more efficient extraction of the round.
9mm AR barrels are threaded 1/2x36 tpi and you'll need a 9mm-specific flash hider or muzzle device too.
9mm Specific Parts
- 9mm Barrel
- 9mm Bolt Carrier Group (ramped - use "DPMS" hammer, unramped - use 9mm hammer)
- 9mm Magwell
- 9mm magazine (modified Uzi)
- 9mm Buffer (optional - recommended)
- 9mm Flash Hider
Generic AR Parts that can be used a 9mm AR
- AR Upper
- AR Lower
- Standard AR Lower Parts Kit (see note about hammer above)
- Charging Handle
- Buffer Spring
- Buffer Tube
- Castle Nut + Lock Plate
- Stock
AR Parts Not Needed
- Gas Block
- Gas Tube
