I had to pass on the Model 20 and 21 (10mm & .45 ACP respectively) due to their double-stack mags and how that raised the diameter of the grip. They still "fit" but not as comfortably as the slightly smaller frames do. My personal perspective was that even a slight discomfort or need to perform a "manual adjustment" would mean that if I were to ever need to fire/use the pistol in a reflexive or rapid-engagement situation, my accuracy would be less consistent than with a pistol whose grip was a 100% fit each and every time. The old saying of "a hit with a .22 is better than a miss with a .44 magnum" translates (at least for me and my personal use) into "being consistent and confident that I will hit with a .40SW is better than being even slightly less confident with a .45ACP." To each their own. But me? I choose the pistol and then work out which caliber.