Set an aiming laser to your red dot or bore without firing a shot. Measure the laser offset at the muzzle, enter it, and print a true-scale letter-size target. Print the PDF at 100% / actual size.
When printing, set scale to Actual size or 100%. Do not use "Fit" or "Shrink to fit". Those settings resize the page and throw off every offset. Measure the 4.00 in bar before using the sheet.
Unload the rifle and verify the chamber is empty. Tape this sheet to a wall, press the muzzle square against the paper centered in the ring that matches your muzzle device, turn on the laser, and read where the dot lands on the grid. Right and up are from behind the rifle. Enter those numbers above.
When printing, set scale to Actual size or 100%. Do not use "Fit" or "Shrink to fit". Those settings resize the page and throw off every offset. Measure the 4.00 in bar before using the sheet.