250gr is probably the most popular bullet weight in a 50, but anything 200 to 300 is hard to argue with. Personally I shoot the 200SW most of the time.

Powder charge, try to find a load that works around 100gr. That is fine for most applications. If you really want to shoot 300, you should shoot the 300gr SW or the 200gr SW or the Barnes TMZ and push them as fast as you accurately can (under 1.5" at 100 yds or forget it).

So is that gun capable of 300 yds? Sure. The question is, are YOU? There is a lot more to shooting 300 yds than just buying a gun that will lethally lob bullets that far. Do you have a place to regularly shoot to 300 yards? Are you prepared to learn how to judge the wind, which could drift your bullet 2 feet either direction at that range in only moderate breezes? Have you invested in a reliable rangefinder that will range out that far (unethical to take those shots without one)? Have you chosen a scope that has some sort of mechanism (BDC, mil-dot, target turrets) that will allow you to adjust your aim for the drop precisely? You can't just "hold over" when your drop is around 45 inches!! Do you use a stand with a steady rest, front AND back built in, or do you have a good bipod and the ability to practice with it? I've made multiple shots at and over 300 yards and every single one was prone off a Harris bipod.

I'm not saying you shouldn't do it, just that I do and I can tell you it is not an easy thing to make consistent, good shots on game at 300 yards. With practice and good equipment I have not blown one yet but I take it very seriously and want each hunter trying it to do the same.