Reloading 410 slugs
WARNING: The information described on this page is for amusement only! Actually doing any of the following is dangerous to life and limb. The data on this page has NOT been tested in an instrumented test barrel and thus I have no real idea how much pressure the loads are producing. These loads could damage or destroy your firearm and possible even damage or kill yourself.

Working up a load for some 410 slugs from Buck Ball and Slug

The slugs: Left: ~127gr Truncated Cone Foster Slug, Center: ~90gr Round Nose Foster Slug, Right: ~80gr Rifled Slug. (click to enlarge)

All the slugs were hollow based slugs. (click to enlarge)
Goals and Methods

Goal: Generate a safe and accurate load for the three slugs pictured to the right.

Method: At the request of that sent me these slug I limited my powder selection to Aliant's 2400, Herco, Blue-Dot and Unique. My analysis started by using a computer model I found a few years ago. Numerical Advanced Internal Ballistic Model (NABM) by Fabrique Scientific is a fairly sophisticated internal ballistic software that simulates the combustion, pressure and dynamics that happen internal to a firearm as it is fired. It is quite remarkable software for being freeware. Although intended for use in metallic rifle and pistol cartridges I have found it work pretty well with 410 slugs loads. I worked up a load for another slug some time ago (see the data at the bottom of the page) and it predicted velocity pretty close.

Since 2400, Herco and Blue-Dot are already in the softwares library I did some analysis using NABM with these three powders and the three slugs. After quite a number of simulations and research on the side I settled on Herco for all three slugs. Of the three powders is seem to produce the greatest velocity compared to peak pressure and did not appear to have any great sensitivity to increases in powder charge.

With the selection of Herco I then found the powder charge that in the simulation produced pressures at the maximum pressure for a 2.5 inch 410 shotgun (12,500psi). Since my test gun was a three inch chamber gun that gave me another 1000psi of safety margin. But I also did not just jump right to the maximum charge in my testing, I worked up to that charge. From this 12,500psi load I step back 1 full grain and 2 full grain in charge weight. So for each slug I had three loads spanning 3 grains. In all three cases the lowest charge was predicted to produce a 9,000-10,000psi loads. Very safe while not so light as to cause problem with the powder burning completely. In the end this worked pretty good. I shot the lightest load first and as long as the velocity was not dramatically different then predicted I continued. In all three cases I felt safe shooting all three loads. For the most part all the velocities were below the predicted by a small amount. The worst was only 130fps below predicted.
Slug Construction

Components for the load laid out. (click to enlarge)
Slug Construction

The load was assembled in the following manner. I started with new Cheddite hulls that were primed with Cheddite Primers from the factory. They were purchase from Precision Reloading along with the rest of the components used here. Starting with the Cheddite hull I added the powder charge. I measured each charge on a digital scale. On top of the powder charge I put half of a Gualandi Cushion Gas Seal Wad (Precision reloading TUWGS410, although a Stump wad from Ballistic Products is identical as far as I can tell) As you can see in the picture to the left there is a whole Gualandi Cushion Gas Seal Wad and half gas cushion in the picture. A pair of Craftsman Handi-Cuts did a great job cutting them squarely in half. On top of the gas seal I put two 3/8 inch thick felt wads with a 1/8 inch nitro over powder card wad on top of that. Finally the slug sat on the card wad. This was all finished off with a nice roll crimp.
127 gr Truncated Cone Foster Slug

Three 3-shot groups at 25 yards (click to enlarge)
Shots for each load are labeled with the load number. Load 3 are the unlabeled holes.
Load and Velocity data

Load 1
Charge: 9.4 gr Herco
Velocity Data:
Low Velocity: 1285fps
Hight Velocity: 1324fps
Average Velocity: 1306fps
Extreme Spreed: 38.96
Std. Deviation: 19.74

Load 2
Charge: 10.4 gr Herco
Velocity Data:
Low Velocity: 1430fps
Hight Velocity: 1458fps
Average Velocity: 1442fps
Extreme Spreed: 27.74
Std. Deviation: 14.42

Load 3
Charge: 11.4 gr Herco
Velocity Data:
Low Velocity: 1531fps
Hight Velocity: 1555fps
Average Velocity: 1543fps
Extreme Spreed: 23.81
Std. Deviation: 12.00

Group size:
Load 1: 8.3 inch
Load 2: 5.3 inch
Load 3: 3.3 inch
90gr Round Nose Foster Slug

Three 3-shot groups at 25 yards (click to enlarge)
Shots for each load are labeled with the load number. Load 3 are the unlabeled holes.
Load and Velocity data

Load 1
Charge: 11.9 gr Herco
Velocity Data:
Low Velocity: 1710fps
Hight Velocity: 1739fps
Average Velocity: 1722fps
Extreme Spreed: 29.01
Std. Deviation: 15.13

Load 2
Charge: 12.9 gr Herco
Velocity Data:
Low Velocity: 1815fps
Hight Velocity: 1836fps
Average Velocity: 1828fps
Extreme Spreed: 21.47
Std. Deviation: 11.35

Load 3
Charge: 13.9 gr Herco
Velocity Data:
Low Velocity: 1915fps
Hight Velocity: 1947fps
Average Velocity: 1930fps
Extreme Spreed: 32.06
Std. Deviation: 16.15

Group size:
Load 1: 5.7 inch
Load 2: 8.0 inch
Load 3: 4.9 inch
80gr Rifled Slug

Load 1: 3-shot groups at 25 yards (click to enlarge)

Load 2: 3-shot groups at 25 yards (click to enlarge)

Load 3: 3-shot groups at 25 yards (click to enlarge)

Load and Velocity data

Load 1
Charge: 12.3 gr Herco
Velocity Data:
Low Velocity: 1823fps
Hight Velocity: 1842fps
Average Velocity: 1834fps
Extreme Spreed: 18.87
Std. Deviation: 10.00

Load 2
Charge: 13.3 gr Herco
Velocity Data:
Low Velocity: 1888fps
Hight Velocity: 1946fps
Average Velocity: 1923fps
Extreme Spreed: 57.99
Std. Deviation: 30.80

Load 3
Charge: 14.3 gr Herco
Velocity Data:
Low Velocity: 2010fps
Hight Velocity: 2033fps
Average Velocity: 2018fps
Extreme Spreed: 22.63
Std. Deviation: 12.72

Group size:
Load 1: 1.5 inch
Load 2: 0.9 inch
Load 3: 1.5 inch
Recovered Components

Recovered Gas Seals(click to enlarge)

Recover Felt cushions (click to enlarge)

Some recovered Components

As you can see cutting the gas seal wads in half to make gas seals worked great. The seals show no melting or damage more than a little powder residue. Some of the seals were moving more that 2000fps down that barrel. I am really happy with these for gas seal for slug loads. I just have to find better spacers.

The felt did OK as you can see in the picture some of them only have powder residue on one side. I think this was due to them not compressing uniformly. No doubt this effected accuracy. I will definitely be trying more ridged spacers in the future.
Conclusions: I was pleased with the load work up. The Herco powder worked well with the loads and produced velocity close to what was predicted by the computer model. I will have to tweak some parameters in the model and see if I can get the model more accurate based on the above data. Cutting the wads in half to form the gas seals also worked very well. I recovered nearly half of the seals laying in the snow and other than a little soot they are in great shape, even the one that came out in excess of 2000fps. I definitely like this way of creating a good gas seal.

Accuracy was not as successful. The heavier two slugs shot quite poorly compared to other slugs I have shot. I don't think this was necessarily the fault of the slugs. I think it may be a combination of my load construction and the particular gun I tested them in. The 127 and 90 grain slugs were a loose fit in the barrel of my Stevens 38B that I used for the testing. The slugs measure about 0.406 inch and my Steven's bore measures 0.409 inch. I think combine that loose barrel-slug fit with sitting the slugs on the hard nitro card wad allowed the slugs to shift around in the shell and as the slug transitioned from the shell's mouth into the forcing cone and down the barrel. In contrast the 80gr slugs were incredibly accurate and I think this is attributed to the fact that they were a tight fit in my particular barrel. I could not drop one of them down the barrel like I could with the other two. This tight fitting slug produced very good groups compared to any other 410 slug I have tested to date.

I think the solution to the two heavier slug's accuracy will be to change the way the space between the gas seal and slug is filled up. One option would be a loose fill the space like the Remington Sluggers but I fear velocity could be lost. I really want to find a good filler that could be force into the hollow base and cause the slug to expand out to fit the barrel tightly. I might just replace the 1/8 card wad with an 1/8 felt wad and see if the felt would serve that purpose. That said several of the felt wads recovered only had powder residue down one side of them. This makes me think that the long felt wad stack may be buckling under the pressure. I really like the way the Barnaul slugs use a long one piece polymer spacer to push the slug. I might have to find something similar to make spacers out of
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