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Shootnstar sent me two of his hi/low powder “booster” casings he makes for the 37mm. Basically, they are lathed down M-169 casings, that the military uses in their Mk-19 auto grenade launcher. Also, the rear primer pocket has been reamed out to accept a #209 shot shell primer. To load the casing, all you do is use a small piece of electrical tape to seal the vent holes.   An additional vent hole was added, centered in the casing, to aid in primer removal and fuse ignition. Once the vent holes are covered, you can fill the high pressure chamber with 1tsp of fffg clean shot or bp. NEVER LOAD THESE WITH SMOKELESS POWDER!!! I use a small funnel to get the powder in there. The primer is then placed in position using the drill press method, where you chuck up a bolt up-side-down and use it as a primer seat. Once loaded, the booster casing is ready to go. It can be used with many projos, but for now they must be muzzle loaded fuse end first, then fired. They do a real nice job of lighting those fuses too.


     To reload them, just knock out the old primer and clean up the casing with water. Let it dry, and it’s ready to use again. They clean up so well, you can hardly tell they’ve ever been fired! If you want to re-load them quickly, just wipe off the top with a moist rag, and dry it, and apply the small piece of electrical tape, and you’re ready to go!!

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I’ll admit, at first I was very skeptical about how these things were going to work. I have also experimented with the M-169 casings, but did not have access to modify them to this extent. So, mine never worked well enough to make them worth while. HOWEVER, I loaded up one of these casings with 1/2tsp of clean shot, and put my standard heavy duty thick walled cardboard tubed projo down the barrel, (as they have to be loaded “mortar style”) and launched it too normal black powder altitude of a hundred feet or so. It burst, so the fuse lit no problem. I then loaded the second one up with a full tsp of fffg clean shot, and  barrel loaded another projo. I fired this one and it sounded like a land cannon going off! The projo went so high, I lost sight of it till it burst!!! At least 400-500’ high! I also tried some of the thinner walled 1/8” tubing projos with these casings. (As a matter of fact, they are so easy to reload, I tried 8 more, all thin walled with the thick pusher wad) and they all threw those projos out of sight, and lit every fuse, and NO duds, and NO blown apart projos!!

    I went from skeptic to admirer that quickly! I have not seen this performance from any other casing! Even the other high/lows I’ve tried out. Most of them require heavy duty side walled tubing, and heavy base pusher wads, plus a generous amount of gorilla glue to hold it all together. Since these vent holes are angled properly, they distribute the force of the lift charge, so no projo blowout!! I’ve even used them to launch BT-56 rocket tubed projos, hot glued together, without blowout.

     I ordered more of these “booster” casings, and made some recommendations as to some simple changes, to make some in 40mm for myself… (As they are made for the MK-19, they are too large to fit in a regular M-203, to keep the average GI from attempting to launch a real one in a 203… (He’d blow himself up…). We’ll see how the new casings perform when they arrive. For now, here’s another photo of what they look like:

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You can order them directly from the maker at: 

Personally, I would highly recommend these casings. Once you try one, you’ll definitely want more of them. I use them extensively now to test my experimental projos, because they will NOT blow through if you construct your projos properly. They also reload up very quickly!! Also, in the literally hundreds of test launches using quite a few different projos, ALL of the fuses lit, and I have had NO duds!! Using standard black powder casings, if you put too much powder in them as a lift charge, they will actually “blow out” the fuse fame in the barrel, so your fuse won’t light. With these casings I can use a full tsp (50 grains of fffg black powder) and the fuse lights EVERY time, AND these things throw a projo one hell of a distance. If you’re used to standard black powder casings, you won’t believe the distance these things give you. Give one a try, and you’ll be ordering more!!!