Download shooting targets
For this airsoft shooting accuracy test you can use any target, where you can see the holes made by BB, and you can measure horizontal and vertical spread using ruler or tape measure.
If you don't want to use ruler, I prepared some shooting targets in PDF with grid lines in cm and inch. You can download and print these targets (they are in A4 or Letter format). If you expect bigger spread than paper size, you can use two papers and stick them together (with duct tape for example). Size of PDF files is 0.2 Mb.
Important, when you are printing these targets, select "Actual size", otherwise printed grid lines may be smaller than 1 cm or 1 inch.