Figure choke from pellet count ?

[Big D]

Are the barrels uncut? There should be approximately 4" of choke constriction in each barrel. Most guns had more choke than yours.

[Pa SxS]

Here is the shot comparison table showing how many pellets were in each manufacturers shot per 1 ounce. Most 12ga's were tested using 1 1/8 oz of shot unless otherwise specified. I've seen Tatum shot used quite a bit in the records. Do the math to figure out how many pellets would be in 1 1/8 oz of shot and figure out the percentages based upon what the factory records show for the number of pellets in the pattern. The gun William is referring to used a 30" circle at 40 yards. Earlier guns were patterned using a 24" circle at 45 yards. The real early guns (underlifters) used a pattern of 18 x 24 at 45 yards. It's important to know the pattern size and distance.