In the COTW book I have it has 4350 powder but it don't say imr. is this the same powder as imr 4350 that's sold nowadays? I'm using 56gr imr4350 with a 154gr bullet and it has a load listed for 60gr with a 160gr bullet. I've gone as high as 58gr imr4350 but I started having real flat primers with the Winchester primer not so bad with cci tho.