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The Slug Gun Doctor

The Slug Gun Doctor

New York gunsmith Dave Klotz has a cure for erratic slug slingers.

By Dave Henderson

While shotguns were never meant to function as rifles, millions of today’s hunters are asking them to do just that. And that’s essentially what makes the tiny Da-Mar Gunsmithing shop with its nondescript storefront a destination at the sleepy crossroads of Weedsport, N.Y.

The village covers less than a square mile. A determined search is required to find the fly speck on a road map. Situated on the state’s northern lake plains between Syracuse and Rochester, Weedsport is widely known for its bitter winters and dirt-track speedway. People also bring or ship their shotguns here from all over the country so that they may benefit from the graces of Da-Mar owner/gunsmith Dave Klotz, also known as the Slug Gun Doctor.

The guy is an acknowledged master at making shotguns — especially slug guns — shoot well. He’s spent his life in slug country and his entire professional career working on recalcitrant shotguns.

“Now, where were we?” he asked, wiping his hands with a shop towel as a customer exited the shop.

“Well, I want this 870 to shoot better,” I replied, a Remington SPS slug gun in my hands.

“Gee, I never heard that one before,” Klotz joked. “But I might be able to help you.”

Bad Vibes

There are many reasons slug guns shoot poorly, but the primary one is vibration. Any force that causes the barrel to shift while a bullet is rushing downbore will obviously change its point of impact.

The Slug Gun DoctorThat movement is more pronounced in a slug gun than a centerfire rifle. Because of velocity differences, a bullet stays in a slug barrel up to twice as long as it does in a centerfire’s. Also, shotguns aren’t tightly built; they have thinner barrels and receiver walls than a rifle does.

The fit between the barrel and receiver is looser as well. After all, a gun firing an expanding pattern of shot doesn’t need a tight-fitting barrel.

If you want a shotgun to shoot and function like a rifle, you’ll have to tighten things, says Klotz. The first thing is mating the barrel to the receiver like a rifle.

In his four decades of accurizing, Dave and his son, Dennis, have pinned barrels to the receivers of literally hundreds of shotguns. The pinning process alone will improve the accuracy of virtually any shotgun, he promises. Epoxy and even plumbers’ tape are used to affix barrels to receivers, but pinning is the most durable and effective method.

The Process

Pinning involves drilling a hole through the side of the receiver and the shank of the barrel, then using a machine screw to hold the receiver and barrel together. The screw can be backed out to remove the barrel for cleaning or exchanging it for another barrel.

“Some guys like to pin through the top of the receiver,” Klotz said while measuring my 870’s receiver. “But then you have remove the cantilever or scope rail if you want to take the barrel off. Going through the side is easier, more efficient and just as strong.”

The Slug Gun DoctorKlotz pretty much has pinning down to a science, and does dozens every year at $55 apiece.

For a 12-gauge 870, he marked a spot on the left receiver wall 1.050 inches back from the front of the receiver (.950 inch for a 20 gauge), and 1.6 inches from the bottom of the receiver (1.550 inches for a 20 gauge).

Using a No. 3 drill bit, he then drilled a hole through the receiver wall and barrel shank. He followed with a No. 3 tapping drill, then threaded the hole for a .250-28 cap screw.

“You need enough depth for five threads,” Dave said as he tapped the hole. “Three threads will carry a screw’s whole load, so this will be plenty strong.”

He ground the shoulder off a .250-28 Allen head screw so it would fit flush with the receiver’s outside wall. Using a special jig, he then ground the screw to length so it penetrated the receiver wall and barrel shank, but stopped just short of the barrel’s interior wall.

Even though such a screw has plenty of purchase, it can gradually back out under the enormous pressure of recoil. Klotz’ insurance that the screw will stay seated against recoil is a drop of red Loctite. That particular grade of fastener will release when heated should you ever choose to remove the barrel.

Klotz said the key to slug gun accuracy is dampening the ambient vibration of the barrel inside the receiver. This helps to make the harmonics of the free-floated barrel consistent from shot to shot.

“After we pinned this one, I put nine shots in an 8-inch group with it at 200 yards,” he said, displaying a 12-gauge Remington 11-87 autoloader that he pinned in the early 1990s. That gun has become the poster boy for the process.

Other Factors

There are often other inherent flaws — scars or shortcomings from the manufacturing process — that make a barrel shoot poorly.

Subscribe Today!“I like to hand-lap my barrels using a tight-fitting brush coated with lapping compound,” Klotz said, describing a process of polishing out tool marks and other flaws from the rifling.

Klotz says an amazingly high percentage of barrels have “ragged” muzzles when they come from the factory.

“If the (rifling) grooves don’t all come all the way to the muzzle, you’ll get drag on a portion of the slug as it exits,” Klotz said. “And that ain’t good.”As part of his accurizing process, Klotz routinely polishes the muzzle of all guns that come to his shop, using a polishing ball on a hand drill.

He also noticed that in recent years some barrels that he’d pinned and polished still didn’t perform to his accuracy expectations.

The usual culprit, he’s found, is that the forcing cone (the throat, in riflespeak) was either rough or too short. He lengthens the cone to a full inch and polishes it, a process that almost always enhances accuracy.

The Slug Gun Doctor operates under the philosophy that some slug guns are inherently more accurate than others — but all can be made to shoot better.

For more information on Da-Mar Gunsmithing, visit or call (315) 834-9156.

Reprinted from the July 2007 issue of Buckmasters GunHunter Magazine. Subscribe today to have GunHunter delivered to your home.

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