Do YHM lowers fit Geissele uppers?
YHM lower + Geissele upper: yes, they fit
Yes. Yankee Hill Machine (YHM) AR-15 lowers fit Geissele 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 November 10, 2026.
Our take
Most built setup: the YHM lower with the Geissele Automatics 16 Super upper.
About 1 in 15 YHM lowers in our builds carries a Geissele upper.
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
Geissele makes match grade two stage triggers and the MK16 rail that USASOC chose for the URG-I upper.
Founded 2004, North Wales, Pennsylvania, Made in USA
YHM lowers and Geissele 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. The upper is stripped, so the barrel you pick sets the caliber.
Checked on this YHM lower
Yankee Hill Machine Lower Receiverout of stockand this Geissele upper
Geissele Automatics 16 Super Duty Stripped Upper$1,142.99Most built YHM lowers and Geissele uppers setups
Ranked by how often builders pick the exact pair. Only pairs our rules pass are listed.
#1Yes, they fit30% of these buildsCheck fit
#2Yes, they fit22% of these buildsCheck fit
#3Yes, they fit19% of these buildsCheck fit
#4Yes, they fit7% of these buildsCheck fit
#5Yes, they fit4% of these buildsCheck fit
#6Yes, they fit4% of these buildsCheck fit
#7Yes, they fit4% of these buildsCheck fit
#8Yes, they fit4% of these buildsCheck fit
What YHM and Geissele say
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.
Geissele: The Geissele Super Duty receiver set is made to mil-spec dimensions, is compatible with mil-spec AR-15 parts and uses a standard .154 inch trigger pin.
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 + YHM uppersMost picked
- YHM lowers + BCM uppersSecond most picked
- YHM lowers + PSA uppersSixth most picked
- YHM lowers + Aero uppersSeventh most picked
Other lowers under Geissele uppers
- Aero lowers + Geissele uppersMost picked
- PSA lowers + Geissele uppersSecond most picked
- Radian lowers + Geissele uppersThird most picked
- LMT lowers + Geissele uppersFourth most picked
- Smith & Wesson lowers + Geissele uppersFifth most picked
- BCM lowers + Geissele uppersSixth most picked
- Spike's lowers + Geissele uppersSeventh most picked
- Griffin Armament lowers + Geissele uppersEighth most picked
YHM lowers and Geissele uppers: questions builders ask
Will a Geissele upper fit a YHM lower?
Yes. YHM AR-15 lowers fit Geissele 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 Geissele 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.