[R3V3LATIONS]

Sure Big Teddy,

The differences with the G21, G21 SF, and G21 SF/RTF are all in the grip/frame of the handgun. The G21 was the orginal full size .45ACP offering from Glock. The common complaint with it was that the grip was too big area wise. Larry Vickers did a torture test of one, and the only main suggestion, from what I interpreted from that test, was that the channel behind the magazine well needed an after market plug to increase reliability by keeping sand and the like out. Very reliable, proven gun, and FWIW they are "standard issue"where I work.

The G21 SF is the Short Frame version of the 21, having a smaller collective grip area than the 21 to accomodate glock shooters favoring/needing a full size Glock in .45ACP while still maintaining the checkering/factory grip stippiling pattern on the Glock 21's.

The Glock 21 SF/ RTF differs from the Glock 21 Sf insofar as the grip pattern and factory stippiling are less agressive on the back strap for a "softer" (IMO) feel. This frame is more popular among the glock frames from what I have heard/seen/and read.

My knowledge extends only to the third generation of these firearms. All lines of the Glock 21 are deemed "very" reliable in my department and in my own personal experience with these firearms. To the extent of my knowledge, each line of Glock 21 is as reliable as the next, they ALL have proven reputation for being able to take a beating and still function reliably. Sources for this information I have mentioned are from articles I have read (and now cant find) from L. Vickers, Todd Green, my limited shooting experience, and word of mouth in my law enforcement and shooting communities. HTH