I finally got around to building out this San Tan Tactical STT-15 AR lower today. It was mostly a pleasure to build since the bolt catch and magazine release are factory installed. I dug through my parts bins and scrounged up most of the remaining parts for the build from parts kits leftovers. Aside from a a few springs, detents I had a Battle Arms Development fire control selector, Magpul MOE+ grip and UBR stock and a recycled Geissele SD-E trigger ready to go.
+Much ambidextrousness.
+Good ergos. The support side mag release on many ambi lowers lack leverage and can be tough to operate. Not on the STT-15.
+Tight tolerances.
+Fits tightly on DDM4 upper.
+Massive magwell.
+Has an American flag on it.
-Rear takedown pin spring was a PIA to install. It needed to be shortened and it's captured with a nano-sized socket head set-screw that has to be installed under pressure from the spring. I felt it was a miracle the tiny screw wasn't lost during installation.
-Hammer pin fit was very tight. I can't blame San Tan since Geissele pins are close tolerance, and I think the STT was also on the tight end of the spec.
-Sharp edge below right side mag release could use chamfering.
-Has a damned iguana on it.
-It has an auto icon on the fire control selector but no accommodation for an auto sear. Kinda mall-ninja.
-Flag is backwards (or on the wrong side of the receiver.)
~It's got a finger ledge in front of the trigger guard. I'm used to resting my finger above the trigger guard, on the mag release. I find this a little gimmicky. I may change my mind with some use.
~It has rotation limited integral flush cups behind the takedown pin. I've never used a setup like this but have heard from guys that the sling mount can get in the way when working the fire control selector. We'll see.
I'm leaning back toward the simpler manual of arms and parts commonality found in standard lowers. But, if you're lefty-- or really like ambi lowers, you'll dig the STT-15. It's one of the best setups for southpaws on the market. At $280 MSRP, it's an expensive lower. But, based on the quality of the machining, its unique features and the relative ease of assembly, it's not a bad deal. I paid $600 for a complete Knights SR-15 lower. While KAC is it's own animal, the point is that there is a place in the market for premium AR parts. These are just impressions noted during assembly. We'll have more on the STT-15 soon.
