My first "varmint" rifle was a Savage 219 break action single shot rifle in caliber .22 Hornet which I had converted to .219 Zipper. Killed a lot of crows with it. As my tastes (and pocketbook) improved, I went to such cartridges as the .219 Improved Zipper, which is the wildcat prototype of the .225 Winchester, on a Winchester 1885 Single Shot action.

From there I went to a 6mm/.225, simply the .225 cartridge opened up to take 6mm bullets, and it was a real winner at longer range than the .219 Improved. Although I have no way of proving this, I am confident that in using the larger diameter bullet, the pressure was less. I generally used 60-75 grain bullets, and on occasion killed a deer with one of those loads. Very effective.

If the Savage 219, which was essentially a converted single shot shotgun with a brazed on underlug, could accomodate those calibers, I have no doubt that a solid S/S shotgun action could as well.