Hello all - I've not posted here, but have been reading a good bit.  Great site and thanks to all for sharing.

I have a Swedish 12.7X44R Rolling Block action I plan to install a E.R. Shaw barrel chambered in 45-70.  My question is how much pressure can this combination be expected to handle?  I am NOT interested in pushing any limits here.  Should it be limited to Trapdoor loads which are around 18,000 PSI or so?  OR - will it handle higher smokeless loads..... say for the H&R 45-70 will handle?

Just looking for some general guidance of what to expect.  The barrel is still 3 months or so from delivery.

Thanks to all for any guidance or info.

Ken H>

Ken,
You may want to have a competent gunsmith that is familiar with period rifles check your action over to be on the safe side.

The barrel will take modern/SAAMI pressures, no doubt. The action, maybe, maybe not.

Regarding safe pressure limits in Swede/Danish RBs:

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I've been reading for the last couple of days on Roller strength but had a hard time getting a definitive answer.....  Of course, on an action that's over 100 yrs old I can see why a definitive answer could be hard - if not impossible.

I finally found calculations about breechblock thrust that allows me to sorta get my mind around Roller action strengths and what limits Roller strength.  Based on my reading I can see why a roller action should be limited to trapdoor pressures, and certainly no more than 25K.

Thanks for guidance and info.

Ken H>

Quote:

Ken - shooting 35,000 psi reloads is a fact of not IF but WHEN your rifle will become a parts firearm.

Pedersoli 45-70 Sharps (with modern steel) are PROOF TESTED accordingly with their rifles made with best metal obtainable:
* All Pedersoli rifles are proof tested at the (Italian government) National Firing Proof House with smokeless powder cartridges with a pressure exceeding that of the ‘commercial’ factory made ammunition by 30 %.
... 45-70 Govt-------2000-------29007 ... times 30% equals 37,709 psi and you want to shoot reloads that are only 2000 psi under 45-70 MAXIMUM proof loads!  

As for the modern steel used which your barrel has no quality comparison:
Pedersoli barrels are machined from a chrome moly alloy having the metalurgical composition called 30Cr Mo4  Uni 7845 which is a patented alloy variation developed by Mauser in the 1930s specially for their new M34 light machinegun which has such a rapid rate of fire. The alloy was designed to prevent or minimize the barrel from "walking" the bullets on the target as the barrel heated up. To my knowledge only Mauser, Sako, Mannlicher and Walther use this expensive alloy which Pedersoli buys.
 
For our action frames ( and other parts such as breech blocks etc.) we use a special alloy which is best suited for the "forging" process we use on ALL our Sharps, Rolling Block, Trapdoor, Colt Lightning and forthcoming HiWall rifles.
This alloy is identified as being 18Cr Mo4.
Source: Dick Trenk, Pedersoli USA Factory Representative 

Bluntly speaking: shoot only smokeless reloads in the black powder reload psi range and save your family from possibly writing your obituary!

First, I have did an edit to the post where I mentioned 35K to reflect info I have learned on this site and MUCH more reading of links suggested.  Thanks for the help.

There is no doubt the 45-70 can be loaded to MUCH more than this old man wishes to pull the trigger on.  65 grains of Fg pushing a 340 grain bullet is plenty for me and that is a light trapdoor load since a full trapdoor load would have 70 grains pushing a 500 grain and that 500 grain would give a LOTS more recoil.  I was mainly looking for guidance on strength in case somebody with an H&R Handi rifle pulled out one of their commercial 45-70s saying "Shoot this".

John, that is an interesting chrome moly - I did not realize there were so many different alloy of chrome moly.  I saw E.R. Shaw had the chrome moly barrel, and it's available with some BIG calibers like the .358 Win Mag which really packs a whump.... on both ends!

Thanks again for all the help..

Ken H.

The original Swedish data for allowed service chamber pressures for the 8X58RimmedDanish conversion in 1887 of the 1867 12,7X42R black powder rolling block is 1.990 atmospheres (8mm geväret och dess ammunition, av G. Mörner, Artilleritidskrift 1889, page 45" -- see post #10 by NiklasP in following thread. (You need to Login or Register to view media files and links). This is neary exactly same as service chamber pressure quoted from post WW2 Norma documents "The Norma Gunbug’s Guide (1957)" in thread (You need to Login or Register to view media files and links). The 1887 conversion used reheat-treated 1867 receivers, new innards and barrels. For original 1867 receivers, use of the slightly lower USA standard for original trapdoor rifles is perhaps prudent. Kriggävars comparative chamber pressure for 8X58RD are the 3rd set, most recent data.

Grisen

Ken,
Case heads on 8X58RD and USA 45/70 are nearly/really identical. So much so that some folks use 45/70 or longer cases to make 8X58RD cases (Buffalo Arms, for example) and do not thin or turn down the rims. Just to toss a bit of confusion in, my 8X58RD has same rim diameter and thickness,as well as head diameter, as modern, factory 45/70 brass. So do many others.

Beware the precise chamber dimensions often touted by some gun collectors. Many of us have 8X58RD chambered Swedish rollers that have slightly different chamber dimensions, enough to have headspace issues if one insists on making cases to those specs. Many have groove-to-groove dimensions well above 0,323" -- mine has 0,325" and won't even shoot 0,324" cast bullets well. Many even shoot 0,329" GC cast bullets better, perhaps because those bullets center better in the "oversize" necks and tapered throats.

The 8X58RD for Danish and Norwegian Krag turnbolts is so dimensionally similar to much latter 33Winchester, as well as ballisticallly, that one can begin to have "strange" thoughts about why. FYI: chamber pressures for those turnbolt Krags are more like 3.000 atmos.

Grisen