Do Griffin Armament lowers fit BCM uppers?
Griffin Armament lower + BCM upper: yes, they fit
Yes. Griffin Armament AR-15 lowers fit Bravo Company (BCM) AR-15 uppers. Both are AR-15 size receivers. A real mil-spec keeps AR-15 receivers from different makers close, though not exact, and fit problems show up most when the upper and lower come from different makers. We checked them with the rules the AR builder runs.
Fit comes from the same rules the AR builder runs on every part you add. Build data only ranks the setups; it never decides fit. Checked October 31, 2026.
Our take
Most built setup: the Griffin Armament MK2 Stripped lower with the BCM upper.
BCM is the most picked upper brand on Griffin Armament lowers.
Griffin Armament makes suppressors, muzzle mounts and sights, all in house in Watertown, Wisconsin.
Founded 2005, Watertown, Wisconsin, Made in USA
BCM makes mil-spec AR uppers, barrels and bolt carriers, and it test fires every complete upper and bolt carrier group before it ships.
Founded 2003, Hartland, Wisconsin, Made in USA
Griffin Armament lowers and BCM uppers by platform
Each row is checked on the most built part of that platform from each brand.
| Platform | Fit |
|---|---|
| AR-15 | Yes, they fit |
AR-15: yes, they fit
Both are AR-15 size receivers. This multi caliber lower takes the upper's 5.56 NATO.
Checked on this Griffin Armament lower
Griffin Armament MK2 Stripped Lower Receiver$208.95
Most built Griffin Armament lowers and BCM uppers setups
Ranked by how often builders pick the exact pair. Only pairs our rules pass are listed.
#1Yes, they fit18% of these buildsCheck fit
#2Yes, they fit13% of these buildsCheck fit
#3Yes, they fit5% of these buildsCheck fit
#4Yes, they fit5% of these buildsCheck fit
#5Yes, they fit3% of these buildsCheck fit
#6Yes, they fit3% of these buildsCheck fit
#7Yes, they fit3% of these buildsCheck fit
#8Yes, they fit2% of these buildsCheck fit
What Griffin Armament and BCM say
Griffin Armament: Griffin's MK2 stripped lower comes with left and right bolt catch and release levers and a left side mag release, but not the standard right side mag button.
Griffin Armament: The Griffin MK2 lower takes mil-spec .154 inch trigger pins.
Griffin Armament: Griffin's MK2 ambi stripped lower is built to fit mil-spec lower parts and has a mil-spec fire control pocket.
BCM: BCM M4 uppers are machined from 7075-T6 forgings with a Type III hard coat anodized finish.
BCM: BCM's M4 upper takes barrels with an M4 barrel extension, and the bore is cut slightly undersized for a tight fit, so you may need to warm the receiver to seat the barrel.
Fit is judged from the specs retailers list, which can be missing or wrong. Confirm with the manufacturer before you buy, and have a qualified gunsmith check any build before you fire it.
Other uppers builders put on Griffin Armament lowers
- Griffin Armament lowers + Geissele uppersSecond most picked
Other lowers under BCM uppers
- Aero lowers + BCM uppersMost picked
- PSA lowers + BCM uppersSecond most picked
- BCM lowers + BCM uppersThird most picked
- Smith & Wesson lowers + BCM uppersFourth most picked
- LMT lowers + BCM uppersFifth most picked
- Wilson Combat lowers + BCM uppersSixth most picked
- Sharps Bros lowers + BCM uppersSeventh most picked
- Spike's lowers + BCM uppersNinth most picked
Griffin Armament lowers and BCM uppers: questions builders ask
Will a BCM upper fit a Griffin Armament lower?
Yes. Griffin Armament AR-15 lowers fit BCM AR-15 uppers. Both are AR-15 size receivers.
Do I need a matched upper and lower?
A real mil-spec keeps AR-15 receivers from different makers close, though not exact, and fit problems show up most when the upper and lower come from different makers.
Why might a BCM upper feel loose or tight on a Griffin Armament lower?
Some play between an AR-15 upper and lower is common, but it can get excessive when the two come from different makers, and a tension screw or an Accu-Wedge takes it up.