Do Aero lowers fit CMMG uppers?
Aero lower + CMMG upper: yes, they fit
Yes. Aero Precision AR-15 lowers fit CMMG 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.
One exception: Aero AR-15 lowers are a smaller frame and do not fit CMMG AR-10 (.308) uppers. One catch: AR-10 parts aren't standardized between makers, so ask Aero Precision and CMMG if this lower and upper fit before you buy.
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 Aero Stripped M4E1 lower with the CMMG Resolute 16.10in Upper.
About 1 in 80 Aero lowers in our builds carries a CMMG upper.
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 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 lowers and CMMG 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-10 (.308) | They fit, with a catch |
| AR-15 lower + AR-10 (.308) upper | No, they do not fit |
AR-15: yes, they fit
Both are AR-15 size receivers. An AR-15 lower takes the upper's 5.56 NATO.
Checked on this Aero lower
Aero Precision M4E1 Lower Receiver W/MOE SL Grip & SL-S$233.99, out of stockand this CMMG upper
CMMG Resolute 16.10" Upper 5.56x45mm$403.20AR-10 (.308): they fit, with a catch
AR-10 parts aren't standardized between makers, so ask Aero Precision and CMMG if this lower and upper fit before you buy.
Checked on this Aero lower
Aero Precision AR .308 Lower Receiver W/ Magpul MOE Grip$303.99, out of stockand this CMMG upper
CMMG MK3 Banshee Upper Receiver Group .308 Winchester$840.30AR-15 lower + AR-10 (.308) upper: no, they do not fit
The lower receiver (5.56 NATO) cannot support a AR-10/.308 build.
Checked on this Aero lower
Aero Precision M4E1 Lower Receiver W/MOE SL Grip & SL-S$233.99, out of stockand this CMMG upper
CMMG MK3 Banshee Upper Receiver Group .308 Winchester$840.30Most built Aero lowers and CMMG uppers setups
Ranked by how often builders pick the exact pair. Only pairs our rules pass are listed.
#1Yes, they fit7% of these buildsCheck fit
#2Yes, they fit5% of these buildsCheck fit
#3Yes, they fit4% of these buildsCheck fit
#4Yes, they fit4% of these buildsCheck fit
#5Yes, they fit4% of these buildsCheck fit
#6They fit, with a catch2% of these buildsCheck fit
#7They fit, with a catch2% of these buildsCheck fit
#8Yes, they fit2% of these buildsCheck fit
Watch the frame size. Builders also pair parts our rules say do not fit, like these two: Upper Receiver (AR-10) is large frame (AR-10) but the Lower Receiver (AR-15) is small frame (AR-15 / AR-9).
What Aero and CMMG say
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: The Aero M5 lower is DPMS pattern, but its lower parts kit uses an extended magazine release button to make up for the thicker receiver.
Aero Precision: Aero's M5 lower works with standard AR-308 parts and magazines, but Aero recommends its own M5 lower parts kit, which has custom takedown and pivot pins and an extended magazine catch button.
Aero Precision: The rear takedown pin detent hole on Aero's Gen 2 AR15 lower is threaded for a 4-40 set screw.
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.
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 Aero lowers
- Aero lowers + Aero uppersMost picked
- Aero lowers + BCM uppersSecond most picked
- Aero lowers + Geissele uppersThird most picked
- Aero lowers + Wilson Combat uppersFourth most picked
- Aero lowers + PSA uppersFifth most picked
- Aero lowers + Daniel Defense uppersSixth most picked
- Aero lowers + Radical uppersSeventh most picked
- Aero lowers + YHM uppersEighth most picked
Other lowers under CMMG uppers
- CMMG lowers + CMMG uppersMost picked
- PSA lowers + CMMG uppersSecond most picked
- Smith & Wesson lowers + CMMG uppersFourth most picked
- Wilson Combat lowers + CMMG uppersFifth most picked
Aero lowers and CMMG uppers: questions builders ask
Will a CMMG upper fit an Aero lower?
Yes. Aero AR-15 lowers fit CMMG 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.
Does an Aero AR-10 lower fit a CMMG upper?
Aero AR-10 (.308) lowers fit CMMG AR-10 (.308) uppers, with one thing to check. AR-10 parts aren't standardized between makers, so ask Aero Precision and CMMG if this lower and upper fit before you buy. Aero AR-15 lowers are a smaller frame and do not fit CMMG AR-10 (.308) uppers.
Why might a CMMG upper feel loose or tight on an Aero 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.