After I bought the Peters Stahl 22 Conversion, I found myself talking to Larry Nelson of Nelson Custom about 22 conversion units in general. He explained to me that all 22 conversion currently being sold were based on either the Ciener or Marvel design. The Ciener design is a replacement slide that reciprocates in it's entirely, per Browning (approximately). The Marvel design is a replacement slide very much like the S&W M41 slide in design, with a fixed slide and sliding breech block. Larry told me that Bob Marvel is currently working directly with him to perfect the Nelson Custom slide. By "perfect", he means to have it drop in with zero or very slight fiddling about, and to have it feed reliably with any ammo. Well, I finally got around to installing the Nelson Custom unit on an SA MilSpec, and it was a drop in fit. I slide the slide on, installed the Marvel designed slide stop (designed to allow free motion of the arm for slide lockback while simultaneously permitting solid lockdown of the slide on the pin - Simple and clever), snugged up the locking stud which cams the slide down on the pin and also serves as the guide rod... And I was done. About 60 seconds the very first time. I won't be able to shoot it until next week, but it sure is a beauty. According to Larry Nelson, Bob Marvel, and Rob Leatham, it really shoots. I'll be taking it to the range next weekend.