Whats the max powder charge of 777 I can load into my Huntsman SS 50 Cal? Can I shoot 150 grains?

I am using 300 grain Hornaday SST bullets.

Read your manual. It should tell you what the max loads that are allowed for your rifle and under what kinds of powders and bullet weights. I have never seen a manual for the Huntsman so I will not guess. Since it is advertised I believe as a magnum capable I would guess that three 50 grain pellets would be allowed.

Now before you go off loading three 50 grain pellets, remember.. not all rifles shoot their best groups with magnum loads. What is the use of pushing a projectile with three pellets if you can not place the bullet where you want it? If I were you, I'd start out shooting two fifty grain pellets and a projectile and see what kind of accuracy you get with that. If you can shoot good groups with 100 grains of powder, that is normally all the power you will need for most hunting.

Once you're sure the rifle will group with 100 grains, go ahead and try 150 grains and see what happens. Most likely the accuracy of the rifle will drop off, you will take a good pounding on the range from the recoil, and you wallet will empty fast buying those expensive pellets.

Save some money, get loose powder and a see through powder measure. Start your loads at 85 grains of FFG powderand shoot a three shot group. If the group looks reasonably tight, then up the loose powder charge to 95 grains and shoot another group. Keep upping the charge until the groups fall apart, your shoulder falls apart, or you reach the maximum allowed loose power load for your rifle.

The important thing is find a load you can shoot accurately that your rifle likes. The rest is just a matter of shot placement and letting the bullet do the work for you after that.

im not sure about the NEF huntsman, but my NEF Sidekick manual says a max of 150g (pellets only!) and a max of 120g of loose powder