Do YHM lowers and uppers fit together?
YHM lower + upper: yes, they fit
Yes. Yankee Hill Machine (YHM) AR-15 lowers and uppers fit together. 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 YHM .223 Rem/5.56 Billet lower with the YHM .223 Rem/5.56 Billet upper.
YHM is the most picked upper brand on YHM lowers.
Yankee Hill Machine (YHM) makes suppressors, handguards, muzzle devices and gas blocks at fair prices, from a family shop in western Massachusetts.
Founded 1951, Easthampton, Massachusetts, Made in USA
YHM lowers and lowers 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. The upper is stripped, so the barrel you pick sets the caliber.
Checked on this YHM lower
Yankee Hill Machine .223 Rem/5.56 Billet Lower Receiver$245.75and this YHM lower
Yankee Hill Machine Billet Upper Receiverout of stockMost built YHM lowers and lowers setups
Ranked by how often builders pick the exact pair. Only pairs our rules pass are listed.
#1Yes, they fit14% of these buildsCheck fit
#2Yes, they fit11% of these buildsCheck fit
#3Yes, they fit11% of these buildsCheck fit
#4Yes, they fit11% of these buildsCheck fit
#5Yes, they fit11% of these buildsCheck fit
#6Yes, they fit11% of these buildsCheck fit
#7Yes, they fit5% of these buildsCheck fit
#8Yes, they fit5% of these buildsCheck fit
What YHM says
YHM: YHM sells complete and stripped uppers and lowers, plus its own carbines.
YHM: The lower in YHM's billet receiver set fits all standard parts except a trigger guard, has a built in tension screw and takes every generation of PMAG.
YHM: YHM's A3 upper has M4 style feed ramps and T marks, and accepts standard upper parts and mil-spec lower receivers.
YHM: YHM's stripped A3 upper comes without the forward assist and dust cover, while the A3 upper assembly includes both.
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 YHM lowers
- YHM lowers + BCM uppersSecond most picked
Other lowers under YHM uppers
- Aero lowers + YHM uppersSecond most picked
- PSA lowers + YHM uppersFourth most picked
YHM lowers and uppers: questions builders ask
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 YHM upper feel loose or tight on a YHM 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.