Reloading with a 4895, W748 and any powder will require load testing to get tight groups from any rifle. Start a couple grains below what you have tried. Load 3 rounds w/ 42gr W748, 3 rounds w/ 42.3, 3 w/ 42.6, 42.9, 43.2...etc. You'll notice the three round groups get tighter and looser...you'll finally discover the right powder charge/primer combo that gives you a tight group w/ the 168gr bullet. Use the same process for different powders and different bullets or primers. Once you think you've got a very good load, start experimenting with bullet seating depth. The perfect load for that particular rifle is out there...takes a little work finding it.
I prefer 168gr SMK w/ 41.5gr of H4895 in my M1A. That load in that rifle will put holes in holes all day long if I do my part. I also use W748 as well. Each rifle is unique....
IMR4895 usually take a couple more grains than H4895...look it up:
http://data.hodgdon.com/cartridge_load.asp