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Looking at putting up another pattern board.
Would like to catch 99% of the shot pattern at a distance of 40 yards.
The pattern board will be used with a wide variety of shells, shotguns, and chokes.
No shot larger than # 7�.
How big of a pattern board is needed ?
What dimensions ?
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8x8 ft (two 4x8 sheets of plywood) should catch over 90% at 40 yds. If 30% of pattern is within 30 inch circle and center of pattern is within an inch of center of patterning board, you could get close to 95% with 8x8 ft board. If I wanted to capture close to 99%, I would probably go at least 12x12 ft.
You'd be measuring your pattern with a 30-inch circle, so most pattern boards are around 40 to 48-inch square, with the center of the board mounted approximately 4-feet above ground level.
Keep in mind, pattern boards are often used to make fit adjustments to adjust pattern point of impact in relation to the boards center aiming spot, so therefore they tend to be around 4-foot square. But, if on the other hand, your gun is already fit, its point of impact is correct, and you are only making barrel choke adjustments to alter pattern percentage within the 30" circle, then you could get by with a smaller board, something like 36-inch square. As long as you are placing the pattern where it needs to be, and is measured within a 30-inch circle.
After re-reading your question, I am now unsure if you intend to pattern a gun for 99% of shot spread to fit inside 30-inch circle at 40 yards, or you intend to catch 99% of the pellet strikes at 40 yards and you could potentially be shooting a spreader choke. The former, my post above, the later, you'd need a huge board, especially if starting from scratch and the gun is not properly fit. Not sure why you'd want such, as the board is not a safety backstop. Maybe something along the lines of a 5-foot, or maybe even 6-foot spread at 40-yards. Taking into account for aiming errors, I'd say an 8-foot square board at minimum.
Gary makes a good point. If you want to capture 99% so your % within the 30 inch diameter circle is accurate to within 1%, I think I would use a smaller board (max of 8x8 ft), and cut open more shells to get more accurate count of pellets per shell for the box you are testing.
you need to use one side of the White House
I use 36" x 36" because you are interested in 99% of the pellets in a 30" circle. What happens with the rest of pattern has little meaning as they are fliers.
What gun and choke are you proposing to use in this test?
I use a 4x8 sheet of osb. After you shoot a fast coat of
rolled on paint sets it up for another one.