On the Hogden website they have some interesting notes about what you can do with there H4895 powder. Basically you can safely load it to a charge of 60% of their max load value. If you do this a hard kicking Magnum would be very mild to shoot. I don't know about whether accuracy is going to go down the toilet, one way to find out I guess...
From their manual
H4895 powder was chosen because it is the slowest burning propellant that ignites uniformly in reduced charges. For yearsweight shown. This works ONLY where H4895 is listed. DO NOT use H4895 in a cartridge where it has not been shown.
H4895 has been the top choice of cast bullet shooters. For this type of shooting, loads are reduced even more than the
hunting loads listed here. To create this type of target and plinking loads, we recommend our 60% rule with H4895: Refer
to our latest reloading manual or the Reloading Data Center found on this website; take the maximum H4895 charge listed
for any given cartridge and multiply it by 60%. The shooter can create a 1500 to 2100 f/s load, depending on the bullet