Do PSA lowers fit Radical Firearms uppers?
PSA lower + Radical upper: yes, they fit
Yes. Palmetto State Armory (PSA) AR-15 lowers fit Radical Firearms 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 October 31, 2026.
Our take
Most built setup: the PSA BLEM Classic Stealth Lower with the Radical 5.56 Barreled Upper.
About 1 in 20 PSA lowers in our builds carries a Radical upper.
PSA sells affordable AR lowers, uppers, BCGs and complete rifles, and it makes them in house from forging to finished part.
Founded 2008, Columbia, South Carolina, Made in USA
Radical Firearms makes low cost complete uppers, lowers and rifles in Stafford, Texas. They machine the guns themselves instead of assembling bought parts.
Founded 2012, Stafford, Texas, Made in USA
PSA lowers and Radical Firearms 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. This multi caliber lower takes the upper's 5.56 NATO.
Checked on this PSA lower
Palmetto State Armory BLEM PSA Classic Stealth Lowerout of stockand this Radical Firearms upper
Radical Firearms 5.56 Barreled Upperout of stockMost built PSA lowers and Radical Firearms uppers setups
Ranked by how often builders pick the exact pair. Only pairs our rules pass are listed.
#1Yes, they fit49% of these buildsCheck fit
#2Yes, they fit13% of these buildsCheck fit
#3Yes, they fit11% of these buildsCheck fit
#4Yes, they fit3% of these buildsCheck fit
#5Yes, they fit3% of these buildsCheck fit
#6Yes, they fit2% of these buildsCheck fit
#7Yes, they fit1% of these buildsCheck fit
#8Yes, they fit1% of these buildsCheck fit
What PSA and Radical Firearms say
PSA: PSA owns its supply chain, including Spartan Forging and DC Machine, from forging the receivers to finishing the muzzle brake.
Radical Firearms: Radical's 5.56 SOCOM complete upper is ready to attach to any mil-spec lower and comes with a bolt carrier group and charging handle.
Radical Firearms: Radical's 5.56 and 300 Blackout uppers run standard 5.56 mags, and 300 Blackout uses the same bolt carrier group as 5.56.
Radical Firearms: Radical's 6.5 Grendel, 7.62x39 and .450 Bushmaster uppers need caliber specific mags, and 20 round mags are recommended for 7.62x39.
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 PSA lowers
- PSA lowers + PSA uppersMost picked
- PSA lowers + BCM uppersSecond most picked
- PSA lowers + Aero uppersThird most picked
- PSA lowers + TacFire uppersFourth most picked
- PSA lowers + Geissele uppersFifth most picked
- PSA lowers + Daniel Defense uppersSeventh most picked
- PSA lowers + Wilson Combat uppersEighth most picked
- PSA lowers + YHM uppersNinth most picked
Other lowers under Radical Firearms uppers
- Aero lowers + Radical uppersSecond most picked
PSA lowers and Radical Firearms uppers: questions builders ask
Will a Radical upper fit a PSA lower?
Yes. PSA AR-15 lowers fit Radical 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 Radical upper feel loose or tight on a PSA 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.