45-70 Martini-Henry safety questions?

[roysclockgun]

Thanks to the group for all the valuable answers that I have gotten in the past!
I have been working up loads for my rifle chambered for 45-70. (See attached link for the photo.)

http://s101.photobucket.com/albums/m78/ ... G_5519.jpg

The barrel is a modern 22 inch replacement, chambered for 45-70, with a twist of one in 19 inches. The receiver began life as a 1885 British military rifle in .577 cal., then in 1897, was converted to chamber .303 British and sent to New Zealand. I don't know when the rifle was imported or when the conversion to 45-70 was done. The work appears to have been done professionally as well as the re blue. The trigger let off is smooth, albeit a little heavier than what I am used to in modern rifles.
I have new Winchester made brass and Berry bullets that are 350 gr. that Graf had on sale in boxes of 500 bullets. I am using standard Winchester large rifle primers.
I started hand loading with IMR3031 and reached 42 gr., at which point the rifle grouped very well at 100 yards, turning in 2 1/4" groups, using the open sights. I then switched over to IMR4064 and worked up to 44 gr., at which point I was getting the same group sizes as with the IMR3031.
I am happy with these groups and will now load simply for having fun with the piece at the range. The recoil is a healthy "thump", but not brutal. I am getting no measureable stretch in the brass after one firing.
My question is, does anyone see danger in continuing to use these loads in a 126 year old receiver? The ony other powder that I have on hand that appears to be suitable for this 45-70, is IMR4198. I have been told by some that I have to use US Springfield "Trapdoor" loads only. I have no desire to go above those levels anyway, but I have also read that the Martini-Henry action is stronger than is the "Trapdoor" action. Opinions please?
Best,
Steven

 

[SJB358]

I think for target shooting and plinking like you are doing you could stick with Trapdoor level loads with Alliant 2400, save a ton of powder and not stress anything. Those 25gr loads will push a 400gr bullet into the 13-1400FPS range and with the 350's, probably just a touch faster. Stick with the published Trapdoor loads and I think you will be safe and have cases that last forever with minimal trimming. Scotty

 

[JD338]

I second Scotty's comments.
A 405 gr bullet at 1300-1400 fps is plenty of thump for big game hunting out to 150 yds and cases will last a long time. Trap door pressures will be kind to your rifle too.

JD338

 

[roysclockgun]

Thank you gentlemen, for the additional data that I could use if I buy more components. My question was regarding what I am using with components on hand, in large quantities. I did refer to published load data, specifically aimed at "45-70 Government (Trapdoor Rifles)", from the 2009 Hodgdon Reloading Manual 2009. My bullet is a copper gilded 350 gr. Under the manual's data for loading 385 gr. cast, gives the starting load for IMR4064 at47 gr., producing 1545 fps and 18,800 CUP. I am well below that with my 350 gr. bullet, only loading 44 gr. of IMR4064. The same goes for the IMR3031 data, where at 42 gr. I am 7gr. lower than the starting load for the 385 gr. bullet.
My question was in regard to the loads mentioned above, that I am using. Later this week, I will report on Chrony readings.
Thank you,
Steven