Tried outa free box of imi 77gr razor core rounds today and my barrel loved them. Anyone know what powder and weight is used. I know they use a 77gr smk and military primers. Is there powder a secret and is there a good alternative to use. If no 41 primers would you use a standard or magnum primer. I have varget, TAC, h4895, but no Rl 15. From reading i may have a good starting point.