Zeroing Backup Sights with the P3 Ultimate Shooting Rest By ctkprecision | November 23, 2015 0 Comment ArmsVault uses the P3 Ultimate Shooting Rest while zeroing backup sights on their Windham AR-15 rifle. A photo posted by ArmsVault (@armsvault) on Nov 22, 2015 at 4:54pm PST More Info: P3 Ultimate Shooting Rest