Do CMMG lowers fit Aero uppers?
CMMG lower + Aero upper: they fit, with a catch
Mostly. CMMG AR-10 (.308) lowers fit Aero Precision AR-10 (.308) uppers, with one thing to check. AR-10 parts aren't standardized between makers, so ask CMMG and Aero Precision if this lower and upper fit before you buy. CMMG and Aero 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 Aero 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 ENDEAVOR MK4/ ZEROED lower with the Aero M4E1 5.56mm Assembled upper.
Aero 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
Aero makes forged AR receivers, mainly the M4E1 line, with a billet look that still takes standard mil-spec parts. They also make complete uppers, charging handles and rifles.
Founded 1994, Tacoma, Washington, Made in USA
CMMG lowers and Aero 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-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 Aero Precision if this lower and upper fit before you buy.
Checked on this CMMG lower
CMMG MK3/AR10 Stripped Lower Receiver Coyote Tan$274.99and this Aero upper
Aero Precision M5E1 Enhanced 20\" .308 CMV Upper$639.99, out of stockAR-15: yes, they fit
Both are AR-15 size receivers. This multi caliber lower takes the upper's 5.56 NATO.
Checked on this CMMG lower
CMMG ENDEAVOR MK4/ Lower Receiver ZEROED Triggerout of stockand this Aero upper
Aero Precision M4E1 Threaded Upper$593.99, out of stockAR-15 lower + AR-10 (.308) upper: no, they do not fit
The lower receiver (Multi) cannot support a AR-10/.308 build.
Checked on this CMMG lower
CMMG ENDEAVOR MK4/ Lower Receiver ZEROED Triggerout of stockand this Aero upper
Aero Precision M5E1 Enhanced 20\" .308 CMV Upper$639.99, out of stockMost built CMMG lowers and Aero uppers setups
Ranked by how often builders pick the exact pair. Only pairs our rules pass are listed.
#1They fit, with a catch2% of these buildsCheck fit
#2They fit, with a catch2% of these buildsCheck fit
#3They fit, with a catch2% of these buildsCheck fit
#4They fit, with a catch2% of these buildsCheck fit
#5They fit, with a catch2% of these buildsCheck fit
#6They fit, with a catch2% of these buildsCheck fit
#7They fit, with a catch2% of these buildsCheck fit
#8They fit, with a catch2% of these buildsCheck fit
What CMMG and Aero say
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.
CMMG: CMMG does not guarantee its DISSENT runs right with mil-spec or other aftermarket triggers.
CMMG: CMMG's Mk3 .308 platform is based on the DPMS LR-308 Gen 1 high pattern design.
Aero Precision: The M4E1 upper is forged 7075-T6 with a billet style look, and it still takes a standard barrel nut and mil-spec parts.
Aero Precision: Aero's M5 .308 upper has .2795 inch takedown pin holes and a DPMS high profile (.210) tang, and takes standard DPMS .308 parts.
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 + TacFire uppersThird most picked
- CMMG lowers + BCM uppersFourth most picked
- CMMG lowers + PSA uppersFifth most picked
Other lowers under Aero uppers
- Aero lowers + Aero uppersMost picked
- PSA lowers + Aero uppersSecond most picked
- Wilson Combat lowers + Aero uppersThird most picked
- Spike's lowers + Aero uppersFourth most picked
- Smith & Wesson lowers + Aero uppersFifth most picked
- LMT lowers + Aero uppersSixth most picked
- Sharps Bros lowers + Aero uppersSeventh most picked
- BCM lowers + Aero uppersNinth most picked
CMMG lowers and Aero uppers: questions builders ask
Will an Aero upper fit a CMMG lower?
Mostly. CMMG AR-10 (.308) lowers fit Aero AR-10 (.308) uppers, with one thing to check. AR-10 parts aren't standardized between makers, so ask CMMG and Aero Precision 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 an Aero upper?
CMMG AR-10 (.308) lowers fit Aero AR-10 (.308) uppers, with one thing to check. AR-10 parts aren't standardized between makers, so ask CMMG and Aero Precision if this lower and upper fit before you buy. CMMG AR-15 lowers are a smaller frame and do not fit Aero AR-10 (.308) uppers.
Why might an Aero 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.