45-70 govt 420gr/500gr. load advice

[BigUglyMan]

Some of the top reloaders on here tell me that 50 grains of 3031 is a great load with 400-420 grain bullets in the Marlin 45-70.
Do I trust their judgement? Yes.
Would I load their load in my rifle and shoot it? Yes.

My 418gr cast load in my 1885 is something around there. I got it from Ken Waters book. I'd trust him too. Mine runs 1950 FPS with my load. Can't lay my hands on my data right now, but it's in the neighborhood of 50 gr. May be a hair hot for the 1895 though?

 

[HUNTERROD]

45 70 loads

i use both bullets in my handi rifle, the 500 grn loads favor the IMR4198
the 425 favored IMR3031 with a cornmeal filler
now i dont have the 500 data handy, however i just finished a batch of 420gr, this evening, i use 39 grn of IMR 3031 and 2 grns of cornmeal, then seat the 420 grn bullet to proper seated length, this may vary to firearm chambers, however you just want to compact the cornmeal "slightly" the 420 grn bullets i used were soft casted, croyn'd at roughly1300-1350 fps, the cornmeal filler actually clean the bore as it gets pushed out, kills leading, this load was very accurate, , at 100 yrds i was printing 3.5" groups with my handi rifle

so, the 500 grn loads ill have to chack my load data, but i consulted the lyman manual for cast bullet loads to work up to these
the cornmeal filler load was a friends idea, and it works well

 

[H4831]

My 418gr cast load in my 1885 is something around there. I got it from Ken Waters book. I'd trust him too. Mine runs 1950 FPS with my load. Can't lay my hands on my data right now, but it's in the neighborhood of 50 gr. May be a hair hot for the 1895 though?

Your load is likely not that hot.
Here is a copy of a chart that appeared in the Aug-Sept issue of Handloader magazine. Johnn Peterson gave this copy to me about three years ago.
This issue reports on the results of a major test done on 45-70 Marlins. All loads were chronographed and pressure tested. All loads were tested in all types of modern Marlins.
All his testing was done in breach pressure classes, starting at 45-70 loads that so not exceed 21,000 CUP and going in different blocks to those loads which do not exceed 43,500CUP.
Here is the one that does not exceed 35,000 CUP. I broke it up into two sections, for easier reading.

 

[ben hunchak]

Bruce, what are your thoughts on using the top end loads of 43K in the 45/70 Marlin when the .450 Marlin uses that pressure in the same gun?????.....Ben

 

[H4831]

Ben, Somewhere in the article it states that Marlin wouldn't tell them outright that 43,500 was OK, but neither would they tell them that it was not OK to shoot the 43,500.
Here is the 43,500 chart and note at the bottom they shot every load in an 1895 model Marlin.
My second posting here of the 28,000 loads is about as high as I want to go, and note the relatively high velocity with some of the heavy bullets.
Actually, there are some darn respectable loads in the group that doesn't exceed 21,000 CUP! Like 1,700 fps for a 415 grain cast.