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Full-Capacity Smith Carbine Cases

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Hey :)

The pretty little Smith cavalry carbine is a hoot to shoot!
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But the reproduction cartridges of today hold reduced charges compared to the originals. While paper cartridges can be made for these guns with the correct military powder charges, there is an easier way that I’d like to detail in this thread. The closest of the off the shelf repro cartridges we have available are the black nylon varieties that mimic the original gutta percha hard rubber cases quite well.

These cases only hold about 35 grains of powder compared to the approx. 50 grains of the originals. This is done to provide an accurate charge for competition use, which is certainly well and good for that purpose. But for the curious among us who want to experience the full ballistic capabilities of the Smith carbine in its original military issued power level, it can be a bit lacking.

But we can change that!

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First and foremost, I recommend you use 2Fg black powder or equivalent substitutes for the following procedure if you’d enjoy trying it yourself. Ordnance manual sources indicate original military rounds were loaded with rifle powder, equivalent to 2Fg. Loading these increased capacity cases with hotter powder such as 3Fg or equivalent could be a bit hard on your original or reproduction Smith carbine. If you do decide to use 3Fg powder, just use caution. It is probably fine to do so but just use common sense.

Here you can see two nylon cases for the Smith side by side:
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The case on the right is an unmodified one. Notice the shoulder about a third of the way up the casing that limits the amount of powder that can be placed inside. The case on the left has been bored out still leaving a small bevel near the case bottom for strength. The capacity of an unmodified case is roughly 35 grains when topped with an original style Smith carbine bullet from Era’s Gone but our modified case can hold about 47 grains with the same bullet, boosting powder capacity by 30%.

To make these I first measured the depth of the case by inserting a small dowel rod and marking the dowel flush with the top of the case. Be sure to use a small enough dowel that it can go past the shoulder inside the case and touch the flash hole. Next, get a standard 1/2” drill bit and using the marked dowel rod, place a piece of tape down the shaft of your bit to match the mark on the rod. This will ensure you don’t drill too deep to damage the flash hole.

Now get some double sided tape and wrap each casing with it. This will allow us to carefully hold the case while we drill. I found that not using this can cause the case to rotate to easily in your hand if the drill bit catches inside the case. Using a vice or tool to hold the case is risky as you might crack them, so I recommend doing this step using your hand.

Now put your drill on low speed and insert the bit into the plastic case. Using light pressure, bore out the case. You may need to use a set of needle nose pliers to pull out the plastic shavings as needed. Once you reach near the bottom, use gentle pressure to ensure the bit doesn’t gouge the bottom of the case or damage the touchhole.

Once that’s done, you can use a small sanding drum in your Dremel to clean up any jagged edges inside the case. Remove the double sided tape, clean away any tape residue, and you’re ready to load your cases in the usual fashion.
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Hope this little tutorial helps guys. Keep in mind this might shorten the lifespan of your cases by a bit, but they are cheap and readily available. Many people have tried 30-35 grain charges of hot Swiss 3Fg powder in these cases with no ill effects, so 45 or so grains of 2Fg should pose no issues, and the guns were originally fired and meant to handle these loads, so there should be no safety risk at all provided your original or repro carbine is in good operating condition.

Take care!

-Smokey
 
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Just an FYI. I have used a punch to make round discs out of hair curler paper. Drop a disc into the bottom of your smith case and pour your powder in on top of it. The paper is ultra thin and works great.
 
Ordnance manual sources indicate original military rounds were loaded with rifle powder, equivalent to 2Fg. Loading these increased capacity cases with hotter powder such as 3Fg or equivalent could be a bit hard on your original or reproduction Smith carbine.
Interesting. As mentioned on other old and current threads on Smith Carbines, I have opened an original Smith Carbine case and found the powder as fine or finer than what we call 4F today, regardless of any manual.

The current brass cases I have are either Pietta or dimensional copies of Piettas I have made, and from the ledge down hold 40 grains of 3F. Filled to the top, believe 60 grains. Made some fully bored out brass cases in the past and didn’t care for the loss of accuracy if you weren’t careful with the OAL of the cartridges. The ledge provides a positive stop and at least in my guns, consistently gave the best accuracy. Looking forward to hearing about your results with your modified plastic cases.
 
Like TC, above, I nitrated some brown coffee filter paper, then punched small discs to seat before the powder, Keeps the powder from leading out of the flash hole and ignites very quickly.

ADK Bigfoot
 
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