[studdog]

What a confusing thread!

The 450Marlin and 45/70 are very dissimilar in many ways.  Their individual loadings must be kept seperate.

For example, the only available brass for the 450 is from Hornady.  Starline does not manufacture 450 Marlin brass.

There is no published data for the 450 Marlin using the Rem 405g JSP.  The closest data available is for the 400g Speer, which has a maximum charge of 52.5g of H322.  I only load these to 52.0g as, for me, accuracy drops off with the 52.5g load.

The 450 has 93% of the case capacity of the 45/70.  When using 45/70 load data, the maximum could be reduced by that factor to arrive at a GUESS for the max load in the 450 Marlin. (Note that this method assumes pressure and load density are related and similar between the two cartridges)  In the case of the 440 LBT, 36.7g of H4198 would be my MAX.

 

[studdog]

I haven't tried any cast bullets yet, but I have given the Rem 405g JSP a bit of a workout.

I used the Hodgdon web data, substituting the Rem 405g for the Speer 400g and used a 2.550 COL

With 51g of H322 I get 1815fps at the muzzle.
With 52g of H322 I get 1855fps at the muzzle.

At 50yds I get an average of 7" of penetration with 93% weight retention and a bullet expanded to 1"--this is into a bucket of wet sand.

 

[studdog]

The Remington 405 JSP may be hard to beat at $0.12 each.