Civilian--There are several different makes of speedloader on the market today...they range from the simple, "gravity fed" HKS to the "Hi-tech" spring-powered jobbies like the Safariland Comp III's and the S.L. Variant. Which one is most appropriate to you??? That depends on what qualities you're looking for and what you want the speedloader to "do" for you. I'll give you a brief "thumbnail sketch" of each that I'm familiar with, along with their respective pro's and con's...keep in mind that this is my opinion only, YMMV. The oldest "speedloader" still on the market is the HKS...it is gravity-dependent, i.e., it just "drops" the loaded rounds with a quarter-turn of a knob on top of the loader. If the loader is NOT held straight up vertical, the loaded rounds can "scatter"...same thing if you try to "disengage" the loader before all the rounds have dropped clear of the loader. It is probably the slowest of the speedloaders still available, BUT--they are plentiful, INEXPENSIVE, and VERY SECURE--in other words, they hardly EVER "drop" the loaded rounds before you want 'em dropped. The next step up would be the Safariland Comp II's...also gravity-fed, like the HKS, the Comp II's "drop" the loaded rounds when the loader "bottoms out" against the ejector...they are a little faster than the HKS, but not quite as secure, IMO...however, MANY LEO's used the Comp II's with very good results before the en-masse change to self-stuffers, so...The next step "up" in speedloader technology is the Safariland Comp III...designed primarily for competition use, they are the largest--and fastest--of the currently available speedloaders. They use a coil spring(!) to "propel" the loaded rounds into the chambers when the loader "bottoms out" against the extractor...as a result, they are the fastest loader available...also, the most forgiving as far as the position of the loader and revolver when the reload is performed...its not uncommon to see someone using the Comp III's in competition reload with the gun and loader at a 45 degree angle relative to vertical...something that would NEVER work with the HKS and would be "iffy", at best, with the Comp II's...the downside to the Comp III's is that they are HUGE, they are "sensitive" to being handled roughly--they'll "drop" rounds much more easily than the previously-mentioned types if dropped, for instance...and lastly, some worry about the coil spring being under compression for long periods of time. Personally, I wondered about that too, so...I took two each of the K-frame size and the L-frame size and left 'em loaded for four months...after four months, I couldn't tell that they were any "weaker" or "slower" than any of my other Comp II's...YMMV. The last type of loader that I'm aware of--that'll fit your GP100, anyway--is the S.L. Variant, imported from Germany and sold by Dillon Precision thru their "Blue Press" catalog and their website. These are ALSO spring-loaded but, unlike the Safariland Comp III's, instead of ONE large coil spring, the Variant has one for each cartridge!!! They SEEM a little less likely to "spill" rounds from rough handling than the Comp III's, but...the jury is still out...haven't been using 'em that long!!! They ARE significantly smaller than the Comp III's, however...making them better for CCW, for instance. They are also "adjustable" to fit YOUR gun...a feature I'm not sure is either wise or needed. The BAD NEWS is that they are the most expensive of the lot...$20-$30 EACH, depending on which gun you get 'em for...So, it all depends on WHAT you want the loader to "Do" for you...if its' for a reload AFTER firing the first six, I'd look at all of 'em... depending on whether or not you forsee needing to "move" while reloading, the security of the HKS might or might not be comforting ...if you keep the gun UNLOADED and want the speedloader to put the piece into action as quickly as possible, I'd look at the Safariland Comp III's and the S.L. Variant. Whichever speedloader you decide on, be sure to obtain some "dummy" cartridges and PRACTICE using them...it COULD save your life....mikey357