As others have stated, your Investarms Hawken is a good rifle. Every rifle will have it's favorite load combo. The only way to find that favorite load is get out there and experiment. You may for example start with a load of 55gr. by volume with a 530 round ball patched with .018 pillow ticking lubed with 50/50 mix of olive oil / water. Shoot off a bench starting at 25 yards. Fire a 3 shot string and see how it groups. Walk out and retrieve your spent patches and examine them. They should have remained intact and look good enough to use again. If they are burned through it means they are not doing their job. and accuracy will not be good. If they are burned through you may need to go to a thicker patch or a .535 ball.

Provided the patch looks good , up the powder charge by 5grs and shoot 3 more shots from the bench. Look at your group and you could see the size of the group shrink. Don't worry about where on the target you are hitting for now. Keep increasing the charge by 5grs. until you are shooting a tight group then adjust your sights to the point of impact. Then move your target out to 50 yards and continue the same process. Once you find the load combo that your rifle likes you will enjoy your rifle.