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.

There is no way for anyone to know what powder IMI uses with any certainty. You will have to weigh a loaded cartridge, then pull the bullet and weigh the powder charge. That guarantees you'll get an accurate reading in case you spill some powder. The pulled bullet and empty case weight, subtracted from the loaded round weight, will get you a charge weight if you have an accident.

Accurate-Arms powders used to be sold out of Israel. Some were manufactured in the Czech Republic for them. If you have a ball powder inside your ammo there is a chance that it's AA-2520.

It is impossible to visually confirm one powder over another simply by looking at them.

Varget or H4895 will perform extremely well behind 77 SMK’s.

What barrel length/twist?

16" 1:7

16" 1:7

I've used AA2520 to get similar velocities to IMI 77gr without pressure signs.

I want to know what powder is in Black Hills 77gr, as they get 50-100fps more, and I have not found a powder yet that will get close to that without showing significant pressure signs.