Pin the Barrel: Shotguns are not rifles. Barrels are easily removed and tolerances aren't tight where it slides into the receiver. If the barrel moves and vibrates, it won't deliver consistent accuracy. To fix this, Klotz drills a hole through the side of the receiver and through the shank of the barrel, then inserts an Allen head screw to about five threads deep. The result is a barrel that doesn't wiggle.
Improve the Bore: "Shotgun barrels usually don't leave the factory in a condition that leads to really accurate shooting," says Klotz. "We lap the bore, lengthen the forcing cone, and crown the barrel." The high polish in the bore after lapping helps minimize plastic buildup from sabots, which can degrade accuracy. Extending the forcing cone gives the slug a better transition into the rifling.
Fix The Trigger: It's nearly impossible to shoot well with the creepy 8-pound triggers typical of most production shotguns. "You can't shoot accurately with a trigger like that," Klotz says. His shop used to be a Remington Service Center, and he refitted my model 870 with a trigger that breaks crisply at 2 ¾ pounds.
Use A Better Scope Mount: Klotz doesn't believe in barrels with cantilever scope mounts. "On a shotgun, you need a mount that does not shoot loose and will not bend or break. There wasn't one available, so we designed our own," he says. The Da Mar mount uses six screws (three per side), and each screw is located on the sides of the receiver where the metal is thickest. It features a Weaver-style rail and rings.
Reduce Recoil: To take the sting out of my slug gun, Klotz did some bonus work and installed a Remington SuperCell recoil pad and put a steel plug in the stock to increase its weight. Slug guns are never a pleasure to shoot, but these alterations made a big difference and were no doubt part of the reason my groups improved.