By Dave Henderson
As a means of gainful employment, I shoot more slugs in a year than most of you will shoot in a lifetime. Every session is brutal, and many are fraught with mystery. There are, you see, myriad reasons why slugs go astray, many of which don’t have anything to do with the shotgun.
Nevertheless, everyone wants to look at the gun first, so let’s start there. If the gun and not the ammo is the culprit, vibration will more than likely be the cause of the problem.
Vibration, or harmonics as it is referred to in firearms, is particularly troublesome in slug guns because of their relatively loose construction and the fact that the slug stays in the barrel so long.
A shotgun recoils nearly a half-inch while the slug is still in the barrel. Meanwhile, the barrel moves with the recoil and vibrates because of its loose fit in the receiver.
When you figure that moving the barrel the width of a human hair shifts the point of impact an inch at 100 yards, you can better appreciate the evils of vibration.
Flying bolts, shells, levers, springs and other moving parts all contribute to vibration in semiautomatic guns. So do the rails and forearms of pump guns. That’s why single-shot and bolt-action slug guns are more accurate than pumps or autoloaders. The barrels are both free-floating (not connected to a magazine tube) and attached solidly to the receiver.
One pump gun that has a reputation for accuracy is the Ithaca Deerslayer II. Its fixed free-floating barrel design is unique among pump slug guns.
“Pinning” the barrel to the receiver can make a pump or autoloader more accurate. This typically entails having a gunsmith drill and tap a hole in the forward receiver wall of your gun and installing a set screw long enough to bear tightly against the barrel shank.
Even a loose magazine cap can cause slugs to stray several inches at 100 yards. And imagine the effect of resting a pump gun on its slide when you shoot!
If your slug gun is shooting patterns rather than groups, the most obvious place to look is the load. If you’re shooting a smoothbore, don’t use sabot slugs. They’re designed for rifled bores. A sabot won’t consistently separate from the slug if there’s no rifling in the bore to spin it.
If your gun does have rifling, be advised that different interior barrel dimensions and twist rates will account for one sabot slug shooting better than another.
Shotguns are notoriously rough on scopes; excessive recoil can wreck a scope in a handful of shots. Check the scope and its mounts. If the system is even a bit loose, accuracy will suffer. Only scopes that can withstand the recoil of a .375 Magnum rifle are suitable for use with shotguns.
Few variables affect accuracy more than trigger pull. The pull must be light and crisp. You won’t see what the gun and load is capable of until the trigger pull is in the 3- to 4-pound neighborhood. Regardless of the trigger-pull weight, you must become familiar with the trigger’s break point to get any kind of consistency off a bench.
Let’s face it. Slug shooting is a brutal, bone-jarring, teeth-rattling, ears-ringing, humbling experience. It takes practice and more than a little know-how to shoot a slug gun accurately and get dependable results.
Most slug gun “tests” are conducted in a way that tells the shooter nothing, even though he doesn’t realize it. Slug guns and loads may have progressed a lot over the last 25 years, but shooters haven’t.
Doubt that? Okay, how do you shoot? Is the rest solid? Does it make the gun immovable? Is it soft enough to absorb vibration? How is the gun positioned on the rest? Does it contain the recoil that affects accuracy?
No, a jacket rolled up on the hood of your pickup is not an effective rest.
If you’re shooting a slug gun at the bench, keep the front sling stud 2 inches forward of the front bag to avoid a “bump” when the gun recoils.
Pull back firmly on the pistol grip with the right hand and use the left hand (just behind the rest) to pull the forearm down and to the rear at the same time.
You can shoot off a bench without gripping the forearm, letting the barrel “float.” But remember that a slug gun recoils more than a half-inch while the slug is still in the barrel, and the whole gun is moving. You must control it.
Also, if you sight-in from the bench without pulling the grip toward you and the fore-end down and rearward, you’ll find that the gun shoots low when you fire offhand.
If you’re sighting-in a pump gun, keep the pump handle off the rest. A pump’s slide mechanism is extremely unstable. Grip it with your front hand (while the gun is on the rest, of course) to keep the vibration from throwing slugs all over the paper. I like to rest a pump’s receiver on the bag rather than the slide.
Okay, you’ve got the technique. Now, how much do you know about the effects of wind or mirage?
A slug’s low velocity and large bearing surface make it very vulnerable to winds. An 8-10 mph crosswind - we’re talking a breath of air here; just enough to ripple range flags at a 45-degree angle - will move a 1-ounce 1,500 fps slug nearly 2 inches at 50 yards and 6-8 inches at 100.
Mirage is the effect of those heat waves you see coming off asphalt, vehicle hoods and rooftops on hot days. It rises from the sun-baked ground, and you’ll also see it through the scope as it rises off your shotgun barrel. A few quick shots will heat the barrel 20-30 degrees above the air temperature. In fact, barrel heat and the resultant mirage can be as much of a problem on a cool fall day as it is in the summer heat.
That shimmer actually bends the image you’re looking at, typically moving it higher and left or right, depending on the breeze. Your best bet is to shoot on calm, overcast days and to position the target at least 30 inches above the ground and on grass, never on a stone, concrete or asphalt slab.
If you sight your gun in under one condition and try the same thing (same slugs, rest, target, etc.) the next day with a different wind or cloud cover, you will likely get a totally different result.
Now you know why your slug gun won’t shoot straight.
Reprinted from the July 2005 issue of Buckmasters GunHunter Magazine. Subscribe today to have GunHunter delivered to your home.