etc.) and assuming similar potential accuracy, unless we reduce bullet mass, any velocity increase will also increase recoil and barrel heating, which are both anathema to ideal varminting. So, we need lighter bullets and if we intend to use conventional (affordable) materials lighter bullets must be of smaller caliber. Whence the value of smaller-caliber chamberings.

Feasible Alternatives
While I certainly have no objection to the 19-caliber, the 20-caliber (5mm) is the default option for those who want to shoot the best available plastic-tipped modern varminting bullets. Hence, when my Superior Ballistics Incpartner (By Smalley) and I set out to create a smaller caliber varmint cartridge utilizing the patented and proven superior SMc™ design, we had two likely options: 17- and 20-caliber.

Based upon his personal bad experiences with the 17-caliber, Smalley was completely uninterested in that option. Nevertheless, I built one such gun for my friend Jim Williamson and he is thrilled with that. That chambering is based upon a modified version of the 17 Mach IV and will launch the fine new Hornady 20-grain V-Max at velocities that will allow it to far outperform the original 17 Remington, 25-grain HP load! Recoil of the 17/23 SMc is not worth considering and barrel heating (especially when using moly-plated bullets) is a non-issue.

Nevertheless, both Smalley and I were more interested in a 20-caliber, which is far more similar to a 22-caliber than it is to a 17-caliber – 20-caliber bullets have 83% of the cross-sectional area of 22-caliber bullets while 17-caliber bullets have only 71% of the cross-sectional area of 20-caliber bullets and only 59% of the cross-sectional area of 22-caliber bullets.