Is it generally safe to use a much slower powder in place of a faster one as long as you get full load density?

I have a .375win that I load using a 220gr jacketed bullet with AA1680 poweder. I have a 300gr mold. The AA1680 is probably not suited to such a heavy bullet, but I have a fair amount of H4895 on hand. The H4895 is much slower on the burn rate charts than AA1680. Regardless of what velocities it might produce, I'm assuming that using a full load will at least be safe. Is this a safe assumption on my part?

By those who shoot one extensively, it is generally accepted that you shoot relatively fast powders in the .45-70 with heavy bullets. I did not want my velocity much over 1650 fps and decided on using IMR-4320 (46 grs.) with a 460 grain hard cast gas check. It works great, burns clean, very consistant velocities, and very accurate. This does indeed give me 100% loading density without crunching powder. I think you would be safe in doing this as long as there are some published data for the powder you want to use.

Of course it can be done safely. With the proper amount of powder in place to bring burning pressure and temps up to where the burn is consistent and clean, you can use the right amount of virtually any powder in virtually any case.

In fact, the art of handloading is partially learning through both direct and vicarious experience what weight of a given powder to use, in a given case size, with a given weight of bullet. (First the right amount,min & max, for safety... then the right amount within the min & max parameters for best accuracy.)

4895 may or may not produce the velocities and accuracy you are looking for, but it CAN be used safely, in the right amounts.

I have an old speer reloading manual #10 that lists a load for IMR 4895 for a 235 gr bullet in the 375.It has a max of 36 grains.fill one of your cases with the 4895 and see how much you get in it.I would guess more than 36 grains. I wouldn't try it myself.