A captive dual recoil spring. This seems very stiff, we'll see how it does with my reloads.
Everything up till now seems great, there are a few issues tho.
Some areas of the frame seem rough, mostly around the trigger guard. The movable parts are MIM. Slide stop, safeties...
I purchased the gun through CDNN, they had a BF deal with a Bladetech holster for $329. Haven't been to the range with it yet, but I really like it so far.