My searches have not turned up what I’m looking for: an apples vs. apples comparison of 12 ga. and 20 ga. patterning. What I mean is identical shot charges at substantially identical velocities fired from barrels with similar geometry (e.g., “long” or “short” forcing cones, the same barrel length and the “choke” measured by pattern board performance rather than constriction). I can intuitively accept that a 3″ 20 ga. 1.25 oz. load will not perform as well as a 12 ga. 1.25 oz. load, but I adopt a “show me” attitude at 7/8 oz. and 1 oz. The notion is that modern shot cup wads with a substantial cushion, hard/plated shot and slow burning powder mitigate shot deformation, the reason always stated to be the cause of spottier patterns from a 20 ga.
Have you done such a test? — or know of one?
El Lago, Texas
“Show me” is what it is all about. If there were more people like you, a lot of these after market gun modifying shops would close their doors.
No, I have never done any nose to nose tests of 12 vs 20 as I am not a big fan of the 20 and don’t spend much time on it. I am sure that someone did the work though. International Shooting went to 24 grams (7/8 oz) some years ago for World Championship and Olympic matches. I will absolutely guarantee you that every major country team experimented with the 20, but all of them, and I mean all, stuck with the 12. There has to be a reason.
That reason is almost certainly shorter shot column and less shot deformation. The 12 gauge hull also gives you more options with powder charges, wad cushion construction and potential velocity. Most of the ISU loads are in the 1325-50 area and 7/8 oz from the 20 may not be as consistent at that speed with the constrictions required by the 20s hull.
Shotgun Report’s Technoid
(Often in error, never in doubt.)