A new configuration for my blammy shells

[peternap]

Just to give some background, I've had a ball playing with a few H&R ultra slug guns. They are built like a tank but 12 gauge shotgun shells are made for low pressure.


A very gifted experimenter named Ed Hubel designed a cartridge based on the 50 BMG cae with a rim screwed on. This gave the same head diameter as the 12 ga. Under Federal law, anything larger than .50 is considered a desstructive device if it hasn't been approved for sporting purposes.

Making the head configuration the same as the 12 ga keeps it legal.

The problem I've had is that my lathe isn't exactly a precision machine. I made it and can't thread on it. The rims are small and delicate and I have to make them as slip on units. Then JB Weld or solder them.

I was getting ready to make some and I saw a 12 head that I had been using to cut spacers. I should have been a plumber because I'm always seeing if something will fit on something else.

The brass head off of the shotgun shell was darned close.

The BPI Multi Hull brass heads come off pretty easy with a little heat.





Rather than trying to turn the BMG case on my lathe, I made a mandrel for it and shucked it in my cordless drill. Then using the slack belt grinder, just turned enough so it wasn't quite a slip on fit.

Then I threaded the flash hole for 3/8" per Ed's suggestion in this thread. I threaded a brass rod the same and screwed it in, cut it off and filed it flush.

I'll have to post pictures later about the bushing process. I'll try to make one later this week and take picture as I go.

The bushing has to be reamed fotr two levels. The BPI case has a longer protrusion where the body of the primer goes. There is a second wider depression above that for the primer rim.

Then the flash hole needs to be drilled. I drilled it 0.80 but Ed told me it needed to be bigger for the 209 primers.

Then the head needs to be glued on. I used JB Kwik because it loses it's bond at a lower temperature. If I need to replace the rim, just a quick pass with the torch will let me pull the brass head off.

I pressed the BMG case into the head with an arbor press and now it's ready for fire forming.



I'm making these cases in 3 lengths. 3", 3.5" and 4.25"

The smallest one can hold 150 grains of RE17 and fire a 1200 grain solid.

[MountainDon]

Peter, I love it!   

[NM_Shooter]

Good grief. 

I'd be afraid to be on the buttstock end of that thing, let alone on the business end. 

What sort of velocities are you hoping to acheive? 

Is the barrel rifled?

-f-

[peternap]

Good grief. 

I'd be afraid to be on the buttstock end of that thing, let alone on the business end. 

What sort of velocities are you hoping to acheive? 

Is the barrel rifled?

-f-

With an 800 grain slug, 2100 fps. It can go faster.
I haven't clocked the 1200 grainers yet.