Do CMMG lowers fit TacFire uppers?
CMMG lower + TacFire upper: they fit, with a catch
Mostly. CMMG AR-10 (.308) lowers fit TacFire AR-10 (.308) uppers, with one thing to check. AR-10 parts aren't standardized between makers, so ask CMMG and TacFire if this lower and upper fit before you buy. CMMG and TacFire AR-9 (9mm) and AR-15 lowers and uppers fit each other too. We checked them with the rules the AR builder runs.
One exception: CMMG AR-15 lowers are a smaller frame and do not fit TacFire AR-10 (.308) uppers.
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 November 10, 2026.
Our take
Most built setup: the CMMG MK9 Stripped Lower 9mm with the TacFire 10in Upper 9mm 1:10.
TacFire is one of the most picked upper brands on CMMG lowers.
CMMG makes complete AR rifles, pistols and parts, and it's known for Radial Delayed Blowback, its action for pistol caliber ARs in rounds like 10mm and .45 ACP.
Founded 2002, Boonville, Missouri, Made in USA
TacFire is a dealer only wholesaler, so you'll find its stripped uppers, lower parts kits and AR kits at online retailers, not on its own site.
CMMG lowers and TacFire uppers by platform
Each row is checked on the most built part of that platform from each brand.
| Platform | Fit |
|---|---|
| AR-10 (.308) | They fit, with a catch |
| AR-9 (9mm) | Yes, they fit |
| AR-15 | Yes, they fit |
| AR-15 lower + AR-10 (.308) upper | No, they do not fit |
AR-10 (.308): they fit, with a catch
AR-10 parts aren't standardized between makers, so ask CMMG and TacFire if this lower and upper fit before you buy.
Checked on this CMMG lower
CMMG RESOLUTE MK3/AR10 Lower Receiver Trigger Coyote Tan$599.00and this TacFire upper
Tacfire 18" Upper .308 Win 1:10$395.23AR-9 (9mm): yes, they fit
Both are AR-9 receivers. A 9mm lower takes the upper's 9mm.
Checked on this CMMG lower
CMMG MK9 Stripped Lower 9mm$149.33and this TacFire upper
Tacfire 10" Upper 9mm 1:10$266.98AR-15: yes, they fit
Both are AR-15 size receivers.
Checked on this CMMG lower
CMMG MK4 .223 Remington AR Lower$100.02and this TacFire upper
Tacfire Stripped Upper Receiver$63.05AR-15 lower + AR-10 (.308) upper: no, they do not fit
The lower receiver (.223 Wylde / 5.56 NATO / Multi) cannot support a AR-10/.308 build.
Checked on this CMMG lower
CMMG MK4 .223 Remington AR Lower$100.02and this TacFire upper
Tacfire 18" Upper .308 Win 1:10$395.23Most built CMMG lowers and TacFire uppers setups
Ranked by how often builders pick the exact pair. Only pairs our rules pass are listed.
#1They fit, with a catch8% of these buildsCheck fit
#2They fit, with a catch8% of these buildsCheck fit
#3Yes, they fit5% of these buildsCheck fit
#4Yes, they fit5% of these buildsCheck fit
#5Yes, they fit5% of these buildsCheck fit
#6They fit, with a catch3% of these buildsCheck fit
#7They fit, with a catch3% of these buildsCheck fit
#8They fit, with a catch3% of these buildsCheck fit
What CMMG and TacFire say
CMMG: CMMG's MkGs lower takes 9mm or .40 S&W Glock and SGM magazines and is meant for CMMG MkGs Radial Delayed Blowback uppers only.
CMMG: CMMG's MkG lower takes Glock and SGM .45 ACP magazines and is made for CMMG .45 ACP Radial Delayed Blowback uppers, and other brands' uppers may work but are not guaranteed.
CMMG: A CMMG DISSENT upper fits most of CMMG's BANSHEE, RESOLUTE and ENDEAVOR lowers only after you pull the buffer tube and stock and install the adapter plate that comes with the upper.
TacFire: The UP01C stripped upper is 7075-T6 aluminum with a black hardcoat anodized finish and M4 feed ramps.
TacFire: TacFire's 18 inch .308 complete upper is designed for the AR-10 style platform and sold with a bolt carrier group.
TacFire: TacFire's UP01C stripped upper comes with the dust cover and forward assist installed. It still needs a barrel, BCG, charging handle, handguard, gas block, gas tube and muzzle device.
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 CMMG lowers
- CMMG lowers + CMMG uppersMost picked
- CMMG lowers + Aero uppersSecond most picked
- CMMG lowers + BCM uppersFourth most picked
- CMMG lowers + PSA uppersFifth most picked
Other lowers under TacFire uppers
- PSA lowers + TacFire uppersMost picked
- Smith & Wesson lowers + TacFire uppersSecond most picked
- Sharps Bros lowers + TacFire uppersThird most picked
- Wilson Combat lowers + TacFire uppersFourth most picked
- Aero lowers + TacFire uppersFifth most picked
- Spike's lowers + TacFire uppersSixth most picked
- LMT lowers + TacFire uppersEighth most picked
CMMG lowers and TacFire uppers: questions builders ask
Will a TacFire upper fit a CMMG lower?
Mostly. CMMG AR-10 (.308) lowers fit TacFire AR-10 (.308) uppers, with one thing to check. AR-10 parts aren't standardized between makers, so ask CMMG and TacFire if this lower and upper fit before you buy.
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.
Does a CMMG AR-10 lower fit a TacFire upper?
CMMG AR-10 (.308) lowers fit TacFire AR-10 (.308) uppers, with one thing to check. AR-10 parts aren't standardized between makers, so ask CMMG and TacFire if this lower and upper fit before you buy. CMMG AR-15 lowers are a smaller frame and do not fit TacFire AR-10 (.308) uppers.
Why might a TacFire upper feel loose or tight on a CMMG 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.