First of all you need 48 inch wide sheets for shotgun pattern testing. You should have at least 3 times more target sheets for the choke tubes and cartridges to be tested, then a single test shot may not be determinative.
Onto a corner of target sheets, you should note the “Range”, “Shotgun Information”, “Barrel and Caliber”, “Cartridge Info” etc.
Next, draw one 20” and one 30” circle on the sheet that will help see the the core density, and add a 5” on the center for better aiming at the target. You can also draw these 20” and 30” circles around the center of a resulting pattern, but in this case, you will be unable to test the aiming performance of your shotgun. We suggest drawing the circles beforehand.
For a standard pattering test, it is suggested that you use 32 grams #6 cartridges. For testing skeet or trap shoots, you can use different cartridges and distances. Later on, cut at least 3 cartridges of same type as the ones you will use for your test, and count the number of pellets in them so that you will discover the average amount of pellets in such a cartridge.
For better and accurate results, it is better to conduct tests on a clear and windless day.
After you are done with the preparations, take the gun 40 yards away from the target sheet that you have fixed by any means. It is better the fix the shotgun on a supporting stand, as you may not center your shoot while you are shooting without any support. Following your shoots for desired choke tubes and cartridges, you can now calculate the results.
Simply count the pellet holes in the circle. Use a magic marker, so you don’t lose your place.
Calculate the percentage of the pellets that hit the 30” circle.
You observe 196 pellet holes resulting from your shoot by the cartridge having an average of 280 pellets in it.
Result: 196 (hit pellets) x 100 : 280 (total pellets) = 70% is the pattern efficieny.
You can also learn the POI (Point of Impact) of your shotgun easily. Simply count the pellets on the top half and lower half seperatly. Full (F) choke tube is recommended for POI testing.
Example: 80 of the pellets hit the lower half, and 100 of the pellets hit the upper half from the total of 280 pellets.
Result: 55% of the pattern is above, 45% of pattern is below.
* Note that you must Line up very carefully with the 5” circle on your target sheet resting on top of your front bead. The top rib of your gun must be completely level.
The percentages for diffrent choke tubes are as follows:
- Full Choke: 70% or higher
- Improved Modified: 65%
- Modified: 55-60%
- Quarter Choke: 50%
- Improved Cylinder: 45%
- Skeet No. 1: 35-40%
- Cylinder: 35-40%
Note that these values may change depending of the weather conditions, the catridges used in tests etc.
You can find sample patterning shots on our Facebook page