Stevens 38B Bolt Action 410 Shotgun.
Making a 410 slug-gun out of this old shotgun.
Steven 38B.

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The shotgun as purchased
Goal: The goal of the project is to take this old Stevens 38B bolt action 410 shotgun and make a decent shooting slug-gun out of it.

What I am starting with: Steven 38B bolt action shotgun. The metal is in pretty good condition for a gun manufactured before WWII. Unfortunately the gun as bought has some ugly carving on it. A 24 inch barrel with a full choke. Its chamber for both 2.5 inch and 3 inch shells. Both will feed from its 3rd detachable box magazine.

To do list: First remove the full choke. As you can see in part 1 of my testing, it shoots slugs pretty bad from that full choke. That choke has to go and will likely be removed by cutting down the barrel. This is easy to do and will result in a better cylinder bore than trying to ream the choke out. Velocity lost should be minimal but I will retest and document those changes.

After removing the full choke we need good sights. I settled on some Truglo TRU•BEAD Tyrkey Universal sights (see bottom three picture at the link to Truglo's website). Reasonably priced ($30), has windage and elevation adjustment and come with interchangeable traditional notch or ghost ring for the rear sight. The only thing I have to do is create mounting block to mount the sights. Some details on how I plan to do that are shown below.

Finally the magazine will need to be limited to 2 rounds, 3 rounds total in the gun. This is to comply with Ohio's hunting regulations that limit capacity to 3rds in the gun for deer hunting. I have talked to Ohio Division of Wildlife and disassembling the magazine and putting a block in the bottom to limit capacity will be sufficient. Analogise to plugging your tube fed pump or semi-auto.

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CAD drawing of receiver, barrel and sights.

So my plan at present it to trim the barrel down just enough to completely remove the choke and then mount these sights.

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CAD drawing of front sight.

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CAD drawing of rear sight.

The light gray blocks in the pictures will be CNC machined aluminum blocks that I will epoxy to the barrel. I might end up silver soldering them but epoxy is easier and should prove tough enough if I use the right epoxying and proper surface preparation. The purchased Truglo sights will then just screw to the blocks.
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CAD representation of sight picture.

As a quick view of the sight picture from the shooter's point of view with perspective.
Update 10/11/08

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The trademark on the barrel.

Progress: This week was pretty good. I got the barrel cut down and re-crowned. The bases for the front and back sight machined and I think I have helped the extraction problem

Still to be done: Epoxy the sight to the barrel, plug the magazine, add sling studs to the stock, and get to the range to test both accuracy and velocity.

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Cut and re-crowned muzzle.

I ended up removing 1.5 inches from the muzzle end of the barrel. The original full choke measured 0.390 inch. It now measures 0.4085 at the muzzle and is constant as far in (~0.75in) as my measurement equipment will allow me to measure. I believe the 0.4085 is probably the bore diameter of this particular gun. I probably over did the crown, it is recessed and cut at 11 degree from perpendicular to the bore like most rifles are cut. Given the ranges the gun will likely be shot at the crown is overkill but since I am the machinist why not?

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Front sight parts.

The front sight itself comes with Truglo TRU•BEAD Turkey Universal sights. It actually comes with four different screws for that sight each having one of the common threads that are used for shotgun front beads. The sights are really meant to be mounted to the rib of a shotgun. In my case I selected the 5-40 screw simply because I had the tap and the other screws used less common threads. The block that forms the front sight base on the left side of the picture is CNC milled from 6061 aluminum.

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Rear sight parts.

The rear sight comes from the same set as the front sight. The four screws are 4-40 button cap screws. Like the front sight base the rear sight base is CNC cut from 6061 Aluminum. I have tossed back and forth exactly how I am going to bond the sight bases to the barrel. Silver solder is the tradition method but soldering aluminum is not trivial so I have settled on using 3M Scotch Weld 420 two part epoxy. If I do the surface preparation well I should get shear strengths close to that of silver solder. Given the large surface area of the sight bases I believe the epoxy will hold. For work I have used that same epoxy for bonds in a 12,000rpm 100 Watt transmission and the construction of a mach 2+ wind tunnel model. The only question is whether the epoxy can take the thermal cycling and extreme vibration it will experience in this application.
Update 10/27/08

The completed Stevens 38B slug gun (click to enlarge)
Progress: It's pretty much all done. I cleaned up and sharpened the extractor and this seemed to help the extraction/ejection process some. Sling studs and a sling were added. Most importantly the sight bases were epoxied on.

Still to be done: Get to the range to test both accuracy and velocity. I also need to figure out if and how I am going to refinish the aluminum sight blocks. They're fine for testing at the range but might not be the most convert for hunting. I also have to still make the plug for the magazine. Not a big deal a piece of 3/8 dowel rod would do it but I will probably cut something better looking from some polymer.

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Front sight mounted.

I used Scotch-Weld 420 (Off-White) to epoxy the aluminum sight bases to the barrel. I prepped the barrel by outlining the sight bases and then used some 220 grit emery cloth to rough up the areas on the barrel. I also roughed up the aluminum base where they would contact the barrel. Both got a good cleaning with methyl ethyl ketone to remover all the oils.

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Rear sight mounted.

The action and barrel were clamped in my bench vise and then tweaked until the action was level. That was difficult to determine as there were not many flat spots on that round action to level to. The recoil lug turned out to be the best reference. I used a small line level then to level the sights bases. Epoxy was applied and the bases were clamped in place overnight. Removable locktite was applied to the screws that hold the sights on the bases.

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Sight picture.

Yeah, the 410 slug is underrated be even I don't think it could take the cow elk the sights are on but it made for a good picture in my basement. Probably would have gotten a better picture with more light but the neighbors might not have liked me trying to get a similar picture in the backyard.

I am looking forward to testing it. The gun is light and handy and throws up to the shoulder very nicely. The sights are a nice height and naturally point well. I think the ghost ring rear sight is going to make sight picture acquisition quick and accurate enough for the ranges you would use a 410 slug gun over. Watch for a second test session with this gun to be add soon. Hopefully before deer season.
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