As the owner of an Argentine RB still in .43 Spanish, and several other BPCR's in 45-70, I'd advise against smokeless loads that exceed the moderate loads published in most manuals for the Trapdoor '73 Springfield. I wouldn't feed it with loads recommended for the modern Marlins and Browning '86.
The weight of the barrel will dampen recoil, but add nothing to the strength of the rifle. The RB action is pretty strong, perhaps just behind the Sharps and definitely ahead of the Trapdoor.
It has been my observation that shooters new to the 45-70 want to turn them into sub -.458 Magnums. They and the rifles get beat up and they lose interest in the caliber PDQ.
Don't rule out BP. Try it, you might like it! It's a labour intensive process, but it's what your rifle and the cartridge were designed for. Come over to the "Dark Side" .....
Thanks for the input. The below is info I found online.
The Maximum smokeless loads for a .45-70 as set by SAAMI is 28,000 cup as the safe max, because of the large number of Trapdoor Springfield's still in circulation and use.
Hodgdon Powders limit their online load data for Trapdoor Springfield loads to 28,000 cup while other powder manuals to 18,000 or 24,000 cup for these old blackpowder rifles, but all say the original rifle must be in good shooting condition.
I thought by limiting any smokeless loads to around 26,000 psi and lower would be safe for regular use in a stronger but converted Argentine Rolling Block in .45-70 with a new modern barrel. I have seen pictures of overloaded and blown up RB's and quiet a few split open at the chamber first. Apparently the weakest link in a good condition RB with tight headspace is at the bottom of the chamber where the chamber is thinnest and the barrel least supported.
Most reloading Manuals have 3 sections for the .45-70 cartridge, one for Trapdoor Springfield's and other black powder era 45-70 rifles in good original shooting condition at a max of about 18,000 cup, another for Win 1886 and Marlin 1895 rifles at 28,000 cup and the last for Ruger No.1 & 3 and Siam Mauser's at about 45,000 cup.
So you suggest I should limit it to about 18,000 cup or less?
Looking at the smokeless loads under 18,000 cup online I notice I can push a 300gr. lead bullet at 1839 fps with 51.7gr. of IMR 3031 at 18,700 cup or a 300gr Jacketed hollow point at 1805 fps with 58 gr. of H4895 at 16,500 cup or a 405gr. lead bullet at 1645 fps with 48gr. of H4895 at 18,500 cup.
I think the 300gr. JHP at 1805 fps for a low pressure smokeless 16,500 cup load will do me fine and something I can live with. I prefer using smokeless powder as it is a lot easier to use, cleanup after and store.
I know the Remington Rolling Block action is strong as they used them to make military rifles in 7x57mm, .303, 7.62x54mm Russian and 8mm Lebel among other high pressure smokeless cartridges in the late 1890's about 10-15 years after mine was built and the .45-70 cartridge is a smaller cartridge with less back thrust than the original .43 Spanish cartridge it was first chambered in.
The Belgian government proof house in Liège tried many times to blow one up and could never succeed -
The undersigned Director of the Proving-House for firearms at Liege, certifies having proved on behalf of Messrs. E. & L. Nagant, manufacturers of arms at Liege, a Remington rifle, 50 cal as follows:-
1st proof, 90gr powder, 1 ball, 2 wads.
2nd proof, 750 grain powder, 40 balls, 2 wads.
No damage and nothing extraordinary occurred.
The rifle has received the two corresponding stamps.
(Signed) ....... The Director
Liege Sept 29 1869 Alph. Polain.
There is an addendum to this statement added by the manufacturers.
The barrel could not receive a stronger charge, as the last one filled its entire length, 750 grains of powder and 40 balls occupying 36.31 inches.
(Signed) EM & L.NAGANT
When Val Forgett first starting importing his new made RB's he set about having tests done by an independent lab to see what was possible. My memories a little short on the exact pressure they went up to, but it was at least 150,000 PSI. At that point the lab personnel refused to go any higher. The lock up system held although some of the internal parts didn't survive. Of course these actions were made out of modern steels!
The point to remember is that when the original statement, and the Belgium test was made, about not being able to blow out a RB action, the highest PSI that could be obtained with BP was around 30,000 PSI. The RB action goes back well beyond smokeless powders invention. To the RB's credit though it was able to survive well into the smokeless era, and even today is considered one of the stronger SS actions.
P.O. Ackley Tests Roller to destruction..
September 1953 issue page 70 AMERICAN RIFLEMAN... In a letter in DOPE BAG a writer refers to P.O. Ackley's well known tests of the strength of various military actions.. The writer also says that Ackley also tested other actions including an old pitted rolling block action from a 50-70 which Ackley barreled up in 30 06 Improved and started running his high pressure tests through it.
He finally started getting more notable results when he reached a duplex load of 30 gr. Hi Vel # 2 combined with 30gr 2400 and bulged the barrel, but the action still held.. Finally on the 20th shot with that load the action broke in two from the back of the barrel down through the breech block pin...He says compare that to the 1903 Springfield's which generally blow up on the first shot with that load.. Lol
He went on to say that he used a similar action that had been barreled in 11 mm (a common cal. for the olden days) He rebarreled it to 375 H&H Mag. Tied it to an old tire & fired 10 rounds thru it with no apparent damage..
There was a comment from Gen. Hatcher that detailed some of the tests on rolling blocks in old Government reports .. Like stacking a load of black powder and a bullet on top of it in the barrel & repeating that until the barrel was half full then firing it .. Reporting the action still held...
