I've had a Dutch Beaumont collection for quite a few years. I only have 5 rounds of 43 Beaumont ammo, reformed from 50-90 brass- and only fired 4 rounds of it in the past. Also fired 50 rounds of 45 Colt pistol ammo through the Beaumont rifle using a cartridge insert a bugle restorer made and gave to me. This required putting a 45 Colt round in the adapter, chambering it, firing it, then ejecting brass w/adapter as one piece. Then punching the empty brass out on the bench with a drift/hammer. Then reloading, and doing it all over again. Laborious to say the least...
I recently stumbled across an old net thread where 2 guys claimed they used a brass sleeve collar against the rim at base, to fireform 45-70 to .43 Beaumont. They claimed to use 3/8" and 1/2" sleeves, 1/2" i.d., with .014" wall. This has been put in print before in previous Cartridge Conversion manuals of the 1960's and 70's by 2 different authors.
So I made a trip to my local gun shop, picked up 20 used 45-70 brass for $5, and 45-70 used dies for $25. Also a new can of Trail Boss powder for $19. Loaded up the ammo using 265 grain cast lead pistol bullets, and 16 grains of Trail Boss.
The following tests were all done with a Beaumont rifle strapped to a bench at my range, using a long 30 foot length of rope with a string on the trigger end to fire the gun.
I decided to do a number of different methods to try to fireform the cases. Being they recommended cutting the brass to 3/8" sections, I came up with another easier idea. I bought 1/2" i.d. brass compression fitting ferrules for 36 cents each, and turned the o.d. of each ferrule down so it just fit the chamber of the gun. The ferrules slipped right on the loaded 45-70 shells snugly by hand. I installed these on (3) loaded cases, and fired them. 2 of the cases split just ahead of the sleeve, it was old W-W brittle brass, I did not anneal it. But one case of R-P brass fireformed perfectly. This was newer brass and better metallurgy. ah-HA...
Looking at where the W-W brass split, I decided next to buy two 12" sections of 1/2" i.d. brass tube from Grainger, for $5 each- and cut longer sections to completely cover and reinforce the entire sidewall on 2 loaded shells for the next test. The brass tubing has a .532" o.d. The Beaumont fireformed brass I had, was 1-3/8" sidewall length from rim to where it begins to neck in. So I cut 2 pieces that were 1-3/8" long, and simply slipped those onto two of the loaded 45-70 cases.
I then built up the middle of the case slightly with a strip of masking tape, so it was equal to other fireformed cases I already had. The sleeves had a .532" o.d. but the fireformed cases had a .577" o.d. in the center. So I built it up with tape there to hold the shell perfectly centered while fire forming in the chamber.
This experiment paid off, as the 2 cases with the long 1-3/8" sleeves fireformed PERFECTLY. I am now able to fireform 45-70 to 43 Beaumont with the simple addition of a low cost brass sleeve, that slips on by hand. This cuts the cost of loaded ammunition for the Beaumont about half or less.
I tried a few more experiments- having 6 old rounds of .43 Spanish laying around, I pulled the bullets, dumped the powder, and reloaded it with 16 grains Trail Boss, the bullets were around 300 grain. These shells I built up with only tape, on the base and middle, to fit the chamber. The primers were dinged from previous firing attempts, defective, and were Berdan. I punched them out from the inside, redrilled the pockets for #209 shotgun primers, and used sealer on the primer pockets. Drove the primers home using a piece of copper pipe that fit the Spanish shells perfectly, and came down over the shell and engaged the rims. Resting them on the wooden workbench, I tapped the primers home- then reloaded the shells. All 6 of these shells ignited and fired, and didn't leak from the primer pockets. But all 6 did split the cases. Old brittle brass, even though I had annealed these before loading them up. They had originally been loaded with black powder.
Next experiment was, taking 2 rounds of old 8mm Lebel ammo, and building that case up with tape to fit the chamber. The rim size is nearly spot on. Pulled the bullets, dumped the powder, and reloaded with Trail Boss. Put the original bullets back in place. My intent was fireform the cases in the Beaumont, let the bullets rattle down the bore, and see if it would yield a useable fireformed case. Unfortunately the Berdan primers in the Lebel were no good, so these 2 cases failed to ignite.
Next experiment, purchased a 1-3/8" long, 1/2" i.d. COPPER straight pipe adapter for 69 cents from the hardware store. Pressed that on a loaded 45-70. Had to turn down the o.d. of the copper sleeve a bit to make it fit the chamber, but it fit snug on the shell just like the brass tubes did. This case failed to fire because it had a smaller rim and sunk into the chamber further, escaping the full hit of the firing pin. Upon ejecting the copper sleeve stayed in the chamber. I had to extract the copper sleeve manually with a small dremel sanding drum expanded inside the sleeve, to pull it out. Maybe it's a good thing that one didn't go off, cuz that copper sleeve may have jammed permanently in the chamber.
When it was all done, tests proved that a factory 45-70 case CAN be fireformed to 43 Beaumont, using the LONG 1-3/8" brass sleeve. The resulting brass is nearly perfect.
The short 3/8" compression ferrule will also work, but only if the brass is high quality, and annealed to the proper metallurgy, in this case R-P brass.
The caveat is this- the 45-70 has a smaller rim, and the extractor recess in the side of the bolt head must be carefully and ever so slightly deepened with a small dremel disc, so the extractor travels further inwards towards centerline of the bolt- this way it grabs the smaller 45-70 rim, and pushes the other side of the case against the ejector block, to hold it while extracting/ejecting the spent case.
Another more subtle trick, is do not push the brass sleeve all the way down against the rim. Push it down just far enough to leave a small groove all around for the extractor to grab in to. There's already a small groove in the 45-70 case, don't cover it up.
Cost analysis- buying one length of 12" tubing costs $5, and will yield enough tubing to sleeve (9) shells. This adds $10 to a box of 45-70 Cowboy Action low pressure, low velocity ammo- one should be all in, ammo w/sleeves, for around $40 a box of 20. That's about half the cost of 43 Beaumont ammo built on 50-90 cases. The cost of Beaumont dies for $200/set, empty brass for $40/box, and loaded ammo for $85/box, is highway robbery IMHO. There simply has to be a better way. Pictures to follow.