By Chuck Hawks
The first shotgun "slugs" were probably round, lead "pumpkin balls." These were common projectiles for muskets and shotguns--any sort of smooth bore long arm--for a long time. Unfortunately, the accuracy of a lead ball fired from a smooth bore barrel is pretty sad. Hitting the target is problematical and precise bullet placement is nearly impossible except at very close range. Also, a lead ball has a very poor sectional density (SD), and consequently poor penetration. There had to be a better way.
The answer, of course, was the rifled barrel. Imparting spin to a projectile to stabilize its flight was a quantum improvement in accuracy. Rifled barrels also made possible the conical bullet, and later the familiar spitzer (pointed) bullets used by most hunters today.
But demand remained for some sort of solid projectile that could be fired from a smoothbore gun and used on medium game like deer. Some one-gun families did not own, and could not afford to buy, a rifle. What was needed was an improvement on the lead ball, both in terms of accuracy and penetration.
Foster type rifled slugs
The eventual solution to this problem was the Foster "rifled" slug. This is a short, blunt lead bullet that is solid in front and hollow in the rear, analogous to a badminton bird. And, like a shuttlecock, it is its weight forward balance that allows the Foster slug to fly through the air to its target with reasonable accuracy. Compared to lead balls, this was a big improvement in both accuracy and SD.
Heavy external "rifling" was cast into these Foster type slugs, allegedly to allow the air they flew through to impart a slow spin that would help stabilize the slug. Like most something for nothing schemes, the rifling proved ineffective, but it did provide some space for some compression if the slug had to squeeze through a tight choke. The name "rifled slug" stuck and is still in widespread use today.
Rifled slugs are offered by most of the major ammunition makers in a variety of shotgun gauges, including 12, 16, 20, and .410 bore. They used to be made under bore diameter to allow safe passage through any degree of choke, from full to cylinder. Cylinder bore guns are usually recommended for shooting slugs, but in some cases a full or modified choke barrel will give better accuracy with the undersize slugs.
This may not always hold true these days, however, as Remington advertises that their "Slugger" rifled slugs are made oversize for better sealing against the barrel wall and superior accuracy. Compared to rifle bullets, whose diameter is held to very strict tolerances, Foster type slugs are made to rather haphazard dimensions that vary from one manufacturer to another.
The use of slugs is best confined to single barrel shotguns, either single shot or repeaters. Double guns tend to crossfire with slugs due to the regulation of the barrels.
A smoothbore "slug gun" with rifle sights will usually shoot groups in the 3" (6 MOA) range at 50 yards/meters, making them satisfactory deer hunting weapons at short range. An occasional example will do better, and some do worse. Their effective deer hunting range is limted by their accuracy, but the slug itself is dangerous to other hunters at far greater distances, an important point to keep in mind.
Compared to practically any big game rifle bullet, rifled slugs are not very accurate. They are a short range (100 yard or less) proposition at best. The ballistic coefficient (BC) and sectional density of rifled slugs is pretty pitiful. The only place they score high numbers is in recoil, where low numbers are desired. Shooting groups from a bench rest with a slug gun is not fun, as the recoil is considerable. If possible, always use a rifle in preference to a slug gun for any kind of big game hunting.
Some jurisdictions in the U.S. forbid the use of rifles and mandate the use of shotgun slugs for deer hunting, allegedly for "safety" in crowded hunting areas. I am sure that this is what keeps rifled slugs viable as a sporting proposition. (They are also used in police "riot" guns, of course.)
This is actually kind of funny in an ironic way, as the one thing slugs do really well is penetrate brush. Rifled slugs are probably the most dangerous type of ammunition to use in a wooded area crowded with hunters and other humans, as they plow through visually impenetrable brush, leaves, and small tree limbs with aplomb. A high velocity rifle with a frangible bullet would be far safer in such an environment. I have, for instance, seen .22 varmint bullets fired at very high velocity turn into a puff of blue smoke on a blade of grass!
Conventional Foster type rifled slugs generally weigh 1 ounce in 12 gauge, 4/5 ounce in 16 gauge, 5/8 ounce in 20 gauge, and 1/5 ounce (or 87 grains) in .410 gauge. The 12 gauge slug has an advertised muzzle velocity (MV) of 1560 fps from a 2 3/4" high-brass shell, 1680 fps from a 2 3/4" Magnum shell, or 1760 fps from a 3" Magnum shell. These are Remington figures from their 2004 catalog. The MV's of the other gauges are similar.
The catalog energy figures for the common high-brass ("maximum") 12 gauge slug load are an impressive 2361 ft. lbs. at the muzzle, but only 926 ft. lbs. at 100 yards. This is due to the very poor BC of the slug. Sighted to hit dead on at 50 yards, that slug is 4.8" low at 100 yards. The more powerful 12 gauge slugs are only marginally better, and kick noticeably harder. No matter what, rifled slugs remain a short range proposition.
Stick with 12 gauge Foster type slugs for deer hunting as the smaller gauges pack much less punch. The 20 gauge slug develops only 648 ft. lbs. of energy at 100 yards, which given its low SD is not encouraging. I have done some testing with .410 rifled slugs and they are definitely not adequate deer loads. The less said about these small bore rifled slugs the better.
Brenneke, Buckhammer, and Trophy Slug
These resemble Foster type slugs with one important difference: the wad remains attached to the base of the slug. This provides a better BC and stability in flight, a better shuttlecock, if you will. The assembly is heavier than a plain rifled slug due to the weight of the attached wad. The difference in retained energy at 100 yards is considerable.
The original design of this type, as far as I know, is the German Brenneke slug, offered by Rottweil. Brenneke rifled slugs still use felt and fiber wads, and are suitable for use in smooth or rifled shotgun barrels. Rottweil offers several slug loads in 12, 20, and .410. Their 2 3/4" 12 gauge slug weighs 1 1/4 ounce, and their 3" Magnum 20 gauge slug weighs a full 1 ounce.
A MV of 1476 fps and ME of 2538 are claimed for the 12 gauge 2 3/4" Magnum load. More important is the 100 yard retained energy figure of 1170 ft. lbs.
Fiocchi of Italy offers the Aeroslug Trophy Slug, which appears to be a modernized and simplified version of the Brenneke design. It, too, is recommended for both smooth and rifled barrels. The Fiocchi Trophy slug weighs 1 ounce in 2 3/4" 12 gauge shells, and 7/8 ounce in 2 3/4" 20 gauge shells. Ballistics are similar to the Brenneke loads with somewhat less energy due to the lighter slugs.
Perhaps the most creative design of this general sort, with which I am familiar, is the Remington Buckhammer. It is also the most recent innovation. The Buckhammer lead slug itself is a short truncated cone, rather like a lead "Keith" style revolver bullet. Attached to the base of this is a long, plastic "stabilizer" wad. Remington says that the Buckhammer was designed for use in fully rifled barrels, or with rifled choke tubes. The diameter of the lead slug is supposed to be .73", so I do not see why it could not be used in cylinder bore (smooth) shotgun barrels, but I have not tried it. Experiment at your own risk!
12 gauge Buckhammer slugs weigh 1 1/4 ounces in 2 3/4" cases or 1 3/8 ounces in 3" cases. 20 gauge Buckhammer slugs come only in 2 3/4" cases and weigh 1 ounce.
These Remington Buckhammer loads claim the most impressive ballistics of the bunch. The 12 gauge 2 3/4" load has a MV of 1550 fps and ME of 2935 ft. lbs. The 100 yard figures are 1145 fps and 1600 ft. lbs. Zeroed at 50 yards, the 1 1/4 ounce slug should hit 3.6" low at 100 yards, so it is still a short range load. Naturally, they kick like the very devil in a shotgun of average weight.
The 20 gauge Buckhammer load has a MV of 1500 fps and ME of 2236 ft. lbs. The 100 yard figures are 995 fps and 1074 ft. lbs. Zeroed at 50 yards, the 1 ounce slug should hit 4.6" low at 100 yards.
While still inferior to the 12 gauge loads, the Buckhammer and Brenneke slug loads (which claim similar ballistics) at least get the 20 gauge slug gun up off of its knees. If I had to shoot a smoothbore 20 gauge slug gun, these are the loads I would use.
All three manufacturers of these "super" rifled slugs claim exceptional accuracy in fully rifled barrels. Remington, for example, claims 3" to 3 1/2" 5-shot groups at 100 yards (3.5 MOA or better) with their Buckhammer slugs. Such accuracy would be considered unacceptable from a rifle, of course, but it will take deer at 100 yards.
These days most of the major shotshell manufacturers also offer sabot slug loads for 12 and 20 gauge shotguns. These are for use only in fully rifled barrels. How a long arm with a fully rifled barrel can be termed a "shotgun," I fail to understand, but that is beside the point. These loads are essentially equivalent to the kind of loads used in modern, high performance muzzleloading rifles.
Since the Remington catalog is still open in front of me, I will use their sabot slugs as representative of the type. Bear in mind that, as with sabot bullets for muzzleloaders, they're plenty of variations available.
Remington offers 12 and 20 gauge Premier sabot loads with both JHP bonded lead core bullets and solid copper hollow point bullets. The former are called "Premier Core-Lokt Ultra," and latter are "Premier Copper Solid."
The 12 gauge Core-Lokt Ultra sabot bullet is a .50 caliber, 385 grain HP semi-spitzer. The catalog MV is 1900 fps and the 100 yard velocity is 1648 fps. The ME is given as 3086 ft. lbs. and the remaining energy at 100 yards is 2325 ft. lbs. The trajectory of that load looks like this: +1.8" at 50 yards, +2.4" at 100 yards, and +/- 0" at 150 yards.
The 20 gauge sabot bullet weighs 260 grains. It also has a MV of 1900 fps, and its velocity at 100 yards is given as 1615 fps. The ME is 2084 ft. lbs., and the remaining energy at 100 yards is 1506 ft. lbs. The trajectory of that load looks like this: +2.0" at 50 yards, +2.7" at 100 yards, and +/- 0" at 150 yards.
As I wrote at the outset, this are similar to the ballistics obtainable with high performance, .50 caliber, inline muzzleloading rifles. Accuracy is apparently not quite as good as the best muzzleloaders, as Remington claims consistent 2 1/2" 5-shot groups at 100 yards. But that is impressive accuracy from any kind of shotgun--even if it is really a rifle!
Clearly, the use of these sabot bullet loads completely negates the rationale behind the "shotgun only" deer hunts. Not only are these shotguns with rifled barrels technically rifles, they shoot like rifles. In fact, they equal traditional big game rifle cartridges such as the .45-70 and .38-55.
For example, a .45-70 rifle shooting a 400 grain bullet (BC .214) at a MV of 1900 fps has a trajectory that looks like this: +2.1" at 50 yards, +2.8" at 100 yards, +/- 0" at 150 yards, and -7.2" at 200 yards (Speer figures). That is a very similar trajectory to the Remington Core-Lokt Ultra loads described above.
The Hornady .45 caliber, 300 grain XTP-Mag sabot bullet used in their 12 gauge factory load has a BC of .200, which I suspect is not much different than the BC of the Remington sabot bullet. Holding a scope's horizontal crosswire level with a buck's back should put the bullet into the heart/lung area at 200 yards. Some shotgun!
Slug loads for home defense
Questions about slugs for home defense arise fairly frequently in my mail so, briefly, here is my take on the subject. Shotgun slugs are dangerously over penetrative for most home defense scenarios. (You have no right to endanger your neighbors.) I suggest that, inside of a domicile, #4 buckshot is usually a more appropriate defensive shotgun load.
If you are forced to defend a farm, ranch house, or cabin from external attack, a rifle will probably be superior to a shotgun stuffed with slugs. So I do not see much reason to choose shotgun slug loads for personal defense, except in special circumstances.
Police use of rifled slug loads in the riot guns carried in cruisers is one example of a special circumstance. Many police agencies are reluctant to provide both rifles and shotguns for their patrol cars, so they issue rifled slug loads for use in shotguns. This allows the squad car riot gun to serve as a makeshift rifle if required. Once again, the shotgun becomes a "poor man's rifle."
Slug loads may also be appropriate in some marine applications. In addition to birdshot and buckshot loads, I always kept a pack of rifled slugs handy for my "boat gun," a Mossberg 500 Mariner.
I have primarily concentrated on slug loads for hunting, for which purpose I feel that they are most appropriate. Even so, they are a stop gap alternative to a rifle, primarily useful where rifles are banned for political reasons. Shotgun slug loads intended to be fired from smooth bore barrels manage to combine the worst properties of any hunting projectile: marginal accuracy, low velocity, low sectional density, low ballistic coefficient, rainbow trajectory, and heavy recoil. Nearly the worst of all possible worlds! If you can legally hunt with a rifle, you owe it to both yourself and your quarry to do so. If not, but the law allows the use of fully rifled "shotgun" barrels and saboted projectiles, that is what you should use.
Copyright 2004, 2015 by Chuck Hawks. All rights reserved.