While sitting around, hopefully recuperating, I have been looking through some old American Rifleman magazines from the 1980's & 90's.
I began looking at the pattern tests on new guns or models in the Dope Bag section. Tests were done on an 8 field 30 inch circle at 40 yards for 10 through 20 gauges & at 25 yards for the 28 & .410. A 21.2 circle was drawn concentric to the 30" one & a vertical & horizontal line divided both he inner circle & outer ring into 4ths. As the 21.2 inch circle has half the area o the 30 inch one the 8 fields are equal & contain 88 square inches each.
This 8 field template was carefully centered on the pattern itself, not on the aiming point which was often different. An average of 10 shots was cited. Two things became quickly apparent. 1st was that regardless of bore size, load or choke there did not seem to be a wide variation of number of hits in the 4 fields of either the inner circle or the outer ring.
2nd was that from 12 through 28 there was not a great difference in central core thickening. chokes of skeet & IC generally ran from around 1.25:1 to a bit higher while quarter choke to modified moved up around 1.5:1 going on up around 2:1 as full was approached, seldom did any exceed 2.5:1.
The .410 however was quite a different bird. while admittedly not a , the other an 70 rem bored full. lot of data, as at present I only have three tests to look at. two of these are the two barrels of a Win Model 23 bored mod full, the other an 870 Rem bored full. The model 23 was tested with 1/2 ounce of #7 1/2 size shot containing 185 pellets. Both chokes made re-markedly similar patterns. The mod choke placed 166 pellets in the 30 inch pattern with 142 going into the inner circle & 24 in the outer ring. This is near a 6:1 ratio of central thickening. The Full choke placed 165 pellets in the 30 inches with 139 in the inner circle & 26 in the outer ring for a bit over 5:1 ratio.
The 870 Rem was the absolute worst of the lot, bar none. Load was 11/16 oz of 8 shot containing 248 pellets. It averaged 88% in the 30 inch circle for 218 hits. 199 of the were in the inner circle with only 19 in the outer ring for a ratio of 10.5:1. Personally I find any core thickening ratio exceed 3:1 unacceptable as too much emphasis is placed n an absolutely perfect hold. I am well aware this is the ideal situation, but lets face it, probably 95% of us are simply not that good.
Another thing brought to light, for a given load, regardless of choke the hits in the outer ring did not vary that much. Thus a 45% pattern of 1 oz of #6's should average about 100 hits in the 30 inch circle with a 75% choke placing about 170 its. Appearance is that nearly all of those extra 70 hits will fall within the inner circle. This agrees with the increased ratio of the tighter chokes. It would then appear that dropping from a Full choke to an IC does not actually increase the "Killing circle" as much as we have been led to believe. What it does do is lessen the mangling of game hit with a well centered pattern at the shorter ranges normally associated with upland shooting, for this it is very worthwhile.
Just a few observations while I had not much better to do, so take it for whatever its worth to you. Keep in mind it did not cost you one red cent, so if you gain any help, you got your money's worth, if not it didn't cost you anything so nothing lost other than the time to read it.
