45-70 to 45 cal MZ conversion

[bikerbeans]

Finally finished this one in plenty of time for the Ohio early MZ Season.  The target in the really bad attached pic shows a 100 yard 3 shot 1 1/8" group.  I jumped the trigger a bit on shot number two.  The load in the gun is:
 
200 grain .401" LSWC (40 S&W bullet)
90 grains of BH209
Winchester 777 209 Primer
Harvestor Rib Crush 45/40 sabot.
 
I didn't chrony this load yet but I have chronied jacketed 200 grain 40/45 bullet sabot combos with 90 grains of BH209  at 2,000 FPS.
 
The gun is a hodge-podge of parts from a number of different sources.
 
Huntsman stock set from Fredster22
45-70 22" barrel from auction site
2000 vintage SB1 receiver from local gun shop
New H&R Rail with a 3x9x40 New Style Redfield
22" telescoping rod from Mr. Hubbard
Brass breech plug from Mr. Hubbard - modified with an "o" ring in the primer pocket and epoxied in place no eliminate blowby into the receiver.
Custom Rustoleum Flat Black textured paint on metal surfaces.
$3 used CVA plastic barrel band/ramrod bezel
 
And it will outshoot my friend's fancy T/C smokestick.
 
Dinny, this is the 45/70 barrel we traded back and forth.
 
BB

[Austin from NC]

What ya gonna call it, Frankenstein or Jigsaw either way it'll be a killer.

       Austin

[bikerbeans]

What ya gonna call it, Frankenstein or Jigsaw either way it'll be a killer.

       Austin

I am going to let my assistant, Igor, name this one.
 
BB

[PHATINJUN]

Very nice BB. Kurt

[D Humbarger]

Way to go BB! Congratulations.  I might have to do that conversion if I can't find a Huntsman bbl.
could you post a closeup photo of the breech to see how you converted it?

[bikerbeans]

D Humbarger,
 
My photos ain't so good so I will try and explain the breech modification.  Take a piece of brass round stock and have it turned on a lathe to the OD dimensions of a 45-70 brass that was fired in your chamber and not resized.  Then bore a .41" hole in the brass from the mouth end of the brass to about 1/2" shy of the casehead end.  Then bore a hole in the center of the case head that is large enough to accept a 209 primer and a small "o" ring.  Primer should be just a little proud on the case head so it compresses when the gun is closed.  You also need to bore or flash hole about .035" in the primer pocket recess.  I chamfered the inside of the mouth of the brass to match the bore to help the powder flow into the brass insert.  Once I made sure it worked and fit well I epoxied it in place.  In theory, with heat, the insert would be removable.  I also removed all the ejector parts as they no longer have a function.
 
Another option is to buy a Savage 10ML plug or the banned site plug and have your chamber threaded.  This approach will make cleaning a lot easier but you cannot go back to a 45-70.
 
BB