The 410 slug
I think the 410 slug has gotten a bad rap and is sorely misrepresented by its detractors. There seems to be a lot of critics of the 410 slug but it seems that few of those critics have truly given the 410 slug a really far shake. They go to the range and try a couple old 410 slugs they found in grandpa's gun cabinet and they try them in their 410 squirrel gun. Their squirrel gun of course, has a full choke and sprays the slugs down range like firing buck shot through a rifle slug barrel. From this short and disappointing experience they decide that 410 slugs don't work and never shoot one again. I'm here to say they can and do work if you're willing to give it a real try with the proper equipment and a proper mind set.

First a quick survey of the available 410 slugs on the market. The big three ammunition manufactures, Remington, Winchester and Federal each make a 410 slug. The big three load their 410 slugs in 2.5 inch shells. Winchester also added a 3 inch slug this year (2005). The other two brands I have been able to find are Brenneke and Barnaul and these slugs are loaded in 3 inch shells.

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Winchester 2.5 inch Foster slug 1/5 oz or 87.5 grains
(Actually weighed at 92.8 grains)

Approximate Diameter: 0.387 - 0.392 inch
Overall Length: 0.447 inch
Construction: Standard 2.5 inch Plastic Hull, 209 Primer, Powder Charge, Cupped Cardboard Overpower Wad, Granular Filler, 1/8 in Thick Card Wad, Foster Slug, Roll Crimp

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Winchester 3 inch Foster slug 1/4 oz or 109.375 grains
(Actually weighed at 111.7 grains)

Approximate Diameter: 0.390 - 0.396 inch
Overall Length: 0.493 inch
Construction: Win HS 3 inch Plastic Hull, 209 Primer, Powder Charge, Cupped Cardboard Overpower Wad, Granular Filler, 1/8 in Thick Card Wad, Foster Slug, Roll Crimp
It appears that Winchester simple extended the mold for the 1/5 oz slug. Click here for a side by side picture of the original 1/5oz slug and the new 1/4 oz slug used in these new 3 inch slugs.

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Remington Foster slug 1/5 oz or 87.5 grains
(Actually weighed at 96.1 grains)

Approximate Diameter: 0.400 - 0.405 inch
Overall Length: 0.490 inch
Construction: Standard 2.5 inch Plastic Hull, 209 Primer, Powder Charge, 1/8 in Thick Over-Powder Card Wad, Granular Filler (appear to be shot buffer), Foster Slug, Roll Crimp

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Federal Foster slug 1/4 oz or 109.375 grains
(Actually weighed at 109.0 grains)

Approximate Diameter: 0.395 - 0.399 inch
Overall Length: 0.502 inch
Construction: Standard 2.5 inch Plastic Hull, 209 Primer, Powder Charge, Slug Specific Cushioned Polymer Wad, Foster Slug, Roll Crimp

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Brenneke Foster slug 114 grains
(Actually weighed at 114.9 grains)

Approximate Diameter: 0.412 - 0.415 inch
Overall Length: 1.055 inch Just the slug: 0.537 inch
Construction: Standard 3 inch Plastic Hull, 209 Primer, Powder Charge, Slug Specific Gas Seal Spacer, Attached Seal Brenneke Style Foster Slug, Roll Crimp

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Barnaul Foster slug 97 grains
(Actually weighed at 99.1 grains)

Approximate Diameter: 0.402 - 0.404 with, sabot: 0.425-0.430 inch
Overall Length: 0.445 inch
Construction: Soft Steel 2 7/8 inch hull, Berdan Primer, Powder Charge, Slug Specific Cushion Wad, Two Piece Sabot, Slug, Crimp similar to handgun cartridge.

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Slug Brand / Length Slug Type Slug weight Outside Diameter Inside Diameter OAL Depth of Hollow Base
Winchester 2.5 inch HP (1)
Foster Slug
1/5 oz or 87.5 grains
(Actual 92.8 grains)
0.392 in 0.240 in 0.447 in 0.273 in
Winchester 3 inch HP (1)
Foster Slug
1/4 oz or 109.4 grains
(Actual 111.7 grains)
0.396 in 0.240 in 0.493 in 0.290 in
Remington 2.5 inch FP
Foster Slug
1/5 oz or 87.5 grains
(Actual96.1 grains)
0.405 in 0.255 in 0.481 in 0.365 in
Federal 2.5 inch HP (1)
Foster Slug
1/4 oz or 109.4 grains
(Actual 109.0 grains)
0.399 in 0.245 in 0.475 in 0.270 in
Barnaul 2.875 inch FP
Foster Slug
Sabot (2)
97 grains
(Actual 99.1 grains)
0.404 in 0.255 in 0.445 in 0.275 in
HP = Hollow point
FP = Flat Point

(1)The hollow point slugs have a shallow near hemispherical hollow point. Typical dimensions were diameter of 0.170 inch, depth of 0.060 inch.

(2) Sabot Diameter is 0.425 inch, OAL is 0.795 inch

NOTE: All dimensions are ~ +/- 0.002 inch, except the ID which is ~ +/- 0.005 inch. The inner diameter of the slugs have a taper getting smaller towards the nose, this made it difficult to accurately measure the ID. All slugs have a round bottom to the hollow base as shown in the above drawing.

The first complaint to address is the often touted lack of Kinetic Energy and/or killing power. Because of the relative light weight slugs I see a lot of comparison to 380 ACP or 38 Special. This is a poor comparison in reality. Even when shooting heavier 158 grain 38 special loads the 410 slug has significantly more kinetic energy even out to 100 yards and I don't think anyone would realistically use either cartridge out to that range. The 410 slug out to nearly 50 yards is on par with the venerable 357 magnum and shoots a lot flatter. In the following graph the Kinetic Energy of three 410 slugs (Remington, Federal and Brenneke) is plotted compared with four common handgun cartridges (38 ACP, 38 Special, 357 Magnum, and 41 Remington). As you can see the 410 at short range is only bettered by the 41 Remington.

Even if we use Taylor Knockout values to compare the 410 to the same handgun cartridges we get less disparate but still similar results. Taylor Knockout number is calculated by multiply projectile mass, velocity and bore diameter together as opposed to Kinetic energy that is 0.5 * m * V^2 putting a big emphasis on velocity and completely ignoring bore diameter. Although the 410 slug is lighter it does have significant more velocity and a slightly larger bore than the cartridges it is commonly compared to. As you can see in the follow KTO graph it compares nicely with the 357 magnum out to about 40-50 yards.

The one ballistic problem the 410 slug does have is a horrible BC usually ranging in the 0.045-0.07. This means the slug bleeds energy down range horrible fast. This must be kept in mind when going after animal approaching deer size. Range must be kept short because although you start with respectable amounts of killing power it slips away quickly as the range increases.
One other minor issue with 410 slug as a cartridge is slug construction. Slug manufactures do us a disservice by making them from very soft pure lead or soft lead alloys. Combine the soft lead with the hollow base design of the foster slug (see cutaway picture below) and the result is a very fragile projectile. A harder lead alloy would solve much of this frangibility problem. Brenneke's version of the Foster slug with its integrated polymer gas seal appears to be made of a hard alloy. Remington sluggers that I have fired into a soft clay creek bank have rarely been found intact in my testing. Federal slugs fair better, being a bit heavier they have thicker walls thus making them a bit tougher but still deform badly. The Brenneke slugs resist deformation the best of the three showing very little deformation when recovered from the clay bank and should perform best for penetration when used on deer size targets. Alias, my attempt to test them on the real thing this fall (2004) deer season failed.

Cutaway of a compute model of the Remington Slugger and 119 grain slug from Doug's Slug (no longer in buisness)

Brenneke slug recovered from a clay creek bank about 60 yards away from firing line.
Accuracy? Yes in most 410 shotguns 410 slug accuracy is horrible. And this IMHO is a far bigger issue then kinetic energy when hunting whitetail deer. I don't believe that accuracy is the fault of the cartridge or for that matter the fact that they are fired down a smooth bore. The prime suspect in my study of 410 slug accuracy is the chokes most 410 shotguns have. The large majority of 410 shotguns have a full choke; this is done in an attempt to stretch the range of the very light thin shot pattern the 410 throws. This tight choke makes for a horrible slug gun. The next most common choke in a 410 is modified and the modified choke is only slightly better for shooting slugs but still usually result in mediocre accuracy at best.

The common suggesting when firing fosters slugs is always to say that Improved Cylinder is best. And for many guns this is an acceptable choice but that is because they often to not have access to the best choice. That best choice IMHO is Cylinder bore, not Improved Cylinder, Skeet or anything else; a fixed cylinder bore is better than a Cylinder choke tube.

Think of it this way the fosters slug under the pressure of the propellant gasses has the hollow base swell up to bore diameter as it accelerates down the barrel, then just as it is reaching maximum velocity near the muzzle end of the barrel it runs head long into 0.5 - 3 inches of barrel with tapering constriction. In the case of choke tube it even worst as there is usually a slight step to a larger diameter before getting to this constriction. This sudden deformation of the already expanded slug has to mess with its exit trajectory.

A fixed cylinder bore allows the slug to expand to bore diameter in the forcing cone and then exit the barrel with no changes to the slugs size or contact patch with the barrel through the entire trip down the barrel. I believe this will nearly always give you your best accuracy with a foster style slug but not many guns out there have a fixed cylinder bore and thus you rarely hear it suggested.

The other important factor is the slug fitting the bore. Many manufactures make their slugs significantly under size to ensure that their slug passes through a tight choke with the least likelihood of over-stressing even the thinnest and oldest of shotgun barrels. This results in slugs that have to stretch their base diameter a lot to seal against the bore. It's tuff to ensure the expansion happen uniformly around the base and a non-uniform expansion effects accuracy. A slug that is already close to or even just slightly larger than bore diameter will give the least distortion as the slug expands to bore diameter and thus add to the accuracy.

I have fired a lot of slugs in my Winchester 9410 and despite advertising by Winchester it does not have an improve cylinder choke that shoot like a full choke. My gun as measured has a cylinder bore. There is no constriction and the only anomaly is a lightly etch ring about 0.050 inches thick about half an inch back from the muzzle. This ring has been there since I bought the gun new. The gun patterns shotshells about half way between Skeet and Improved Cylinder. The barrel does shoot slugs very well as seen in some of the follow example groups.

The Remington and Brenneke slugs shoot very well for a smooth bore. I believe this is due to the cylinder bore of the gun (My Winchester 9410) they were tested in and their large diameter. Remington typically measure in the 0.400-0.405 inch range in the few I have cut open. The Brenneke typically measure in the 0.412-0.415 inch range and I have cut many of these open in the process of cutting them down from 3 inch to 2.5 inch so they will chamber correctly in my 9410. Federal slugs shoot poorly and they have the smallest diameter measuring about 0.395-0.399 in the few I have cut open.

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Remington Sluggers 1/5oz

Gun: Winchester 9410

Fire over sandbags at a covered range

Five shot 50yds 2-inch group

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Federal Foster slug 1/4oz

Gun: Winchester 9410

Resting over a 55 gal Drum sitting on another overturn drum

Five shot 50yds 4.5-inch group

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Remington Sluggers 1/5oz

Gun: Winchester 9410

Resting over a 55 gal Drum sitting on another overturn drum

Five shot 50yds 3.25-inch group

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Brenneke Slug 114 grain

NOTE: Modified from 3inch hulls to 2.5 inch hulls

Gun: Winchester 9410

Resting over a 55 gal Drum sitting on another overturn drum

Five shot 50yds 2.75-inch group
Much of this is conjecture and empirical observations from my somewhat limited but diligent experimenting with foster slugs and the 410 bore. I think that if archaeologist can rethink and re-evaluate the T-Rex from the king of the dinosaurs and the apex predator, to reduce him into an over grown turkey vulture; I think it might be possible to get some old dinosaur shooters to take a second look at the 410 slug. This little slug may be capable of more than you think, give it another try.

{Last edited 11/18/06}
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