Okay so I'm about to load of some rounds for my 300 win mag with H1000 powder and 200 gr. Nosler partition and accubond. It says on the powder bottle to max out at 79 gr of powder. So what should I start my rounds at and max at with this being my first bullets to reload.. And what length should a start out at?

Should probably ask in the "Ammunition and Reloading" section.

The Hodgdon Loading Data site is a good start...

First thing I would do is confirm that maximum elsewhere. I don't reload but I'd back off that at least 5% once you've confirmed it. Load say 5 and go to the bench/chrono and see where you are versus published expectations. As for length you could load one to published specs and see if it chambers, fire and chrono it, make sure it ejects well, and look for pressure signs.

I usually start with a factory load that shoots pretty good and work off it's specs. I chrony these loads and build my first load to approach that speed, then advance from there, or in some cases, retract. What the gun wants, the gun gets.

Thanks guys!!! Just really don't wanna blow myself up lol

Every gun will shoot loads differently. Start at the lower end such as in the 72 grs. shown above. Load 3 to 5 rounds and then increase the next batch by a couple tenths of a grain and work your way up to the max shown. Somewhere along the way you will find a load
that shoots better than the rest. I always felt accuracy was better than velocity.

Go to the Nosler load data website and see what they recommend on that powder and bullet. Their suggested accuracy loads have been remarkably correct in several of my rifles of various calibers. Work up to it.

Never mind. They don't show that powder with that bullet.