Since you stated you have lots of H4895 I thought I might dig around for some load data. On Loaddata.com I found a reference using the 220 grain Hornady FP and 38.0 grains of H4895 in a rifle. I also found a 235 grain Speer SP using a max charge of 36.0 grains of IMR 4895 in a Contender. The 4895's are on the slow side for getting top velocity and AA1680, 4198, and RE7 will produce higher velocities. But in this current pandemic environment you might not be able to find any. You can look at 38-55 data and kind of use that as a guideline. I know the 375 Win case is shorter, but compare the overall lengths of the two and this will give you a better idea that they are not that much different in case capacity. I have a Contender S-14 in 38-55 with no brake and have worked up to 40.0 grains of H4895 using the Sierra 200 grain FN seated to an overall length of 2.700 (just touching the lands). This load is clocking 1850 fps in 90+ degree temps. I haven't used it on game yet, but I'm pretty confident it would work fine for deer. I will offer the usual disclaimer that this data was alright in my firearm and should be reduced and worked up to in your firearm. I offer this info because in these times you have to use what you have on hand.