In your opinion, what are the best powders for reloading 300 Win Mag and 375 H&H mag?

I went with mostly H4831sc for the mid weight loads in the 300. A little H1000 if I want to shoot heavier loads and I little H380 if I want to shoot lighter loads. Disclaimer ..... I've never reloaded a rifle cartridge round in my life. This is what I came up with some research and what was available to me within driving distance.
No ideas on the 375. I'm sure others with vastly more experience will chime soon. Maybe even get an ol lord or Fudd comment from Wolfie if you'd post ur just wanting to stock up incase

Playing with a friends 375 remington ultra mag we settled on Aliant reloder 25.

My winmag like's IMR 4831 with 180 grain barnes tsx. Have not tried the sc.

Another thing I learned as a newbie is you can find safe loads on the internet from bullet and powder manufacturers without buying manuals to help get you pointed in right direction as far as common powders for specific bullets and cartridges

Thanks for the responses so far. It's been several ( as in decades) years since I have reloaded for these cartridges. Was a IMR man, but I know there has been a lot of new offerings since then. Just looking to see if there is something better or shinier and more readily available than 4350, 4064, or 4895.

Well according to the Hornady app ( get little deal to have constantly updating manual right in your pocket)

The 375 H&H has a radical different case geometry from the 375 Remington Ultramag
The powders, for the H&H cases are generally two or three levels faster than the extra slow powders for the ultra mag series. While the H&H cases thrive on medium, slow powders, such as Varget H 4350 H 4895.etc.
The ultra mag group uses the very slow powders, such as H 1000 and retumho H870 and even slower.
Generally speaking the larger the case volume compared to the bore diameter, the slower, the powder Hass to be conversely the smaller case capacity compared to bore diameter the faster the powder has to be.
I’ve loaded 300 win mag 300 Weatherby 338 win and 300 ultra mag. I have not loaded for the 375 H&H but a quick check in a loading manual I will show you powders up to cfe223 for the.375H&H.
Once again, generally speaking, the heavier, bullet requires a slower powder and the lighter, the bullet, the faster, the powder in any given chamber and bore diameter. This last little bit of info will help in the final selection of powder, given the choices for that caliber and cartridge and bullet weight.

I had a post on powder a while ago, I like the IMR 4831, thought I used 74 grains but was wrong. Just looked I use 71 grains, it seems to fill the case without compressing. But you want to work your loads up don’t start there. Just because my gun likes that yours might not. Keep an eye out for hi pressure indicators. I used RSW brass I think it is. Hard to find quality 300 win mag brass and it’s expensive. I bought mine off someone on this forum.

Western Wildlife Services

I imagine VV N570 or N568 would work just fine. I bet 24N41 would work in a 375 H&H. I’ll be testing both powders in my 375 EnABELR.

I use N570 for a 195 grain 300 PRC load (3050 fps) and that is very similar to the 300WM for case capacity.

IMR 4350 72gr. with a 165g ballistic tip for my .300 win mag

What's the mv on that? 3500?

Depending on bullet weight, easy button for both would be either IMR4831 or H4831.
Hodgdon has an updated version of their website/ load data up and running. Pick the cartridge and bullet weight, and it will spit out enough data to get you going.

Ive had very good experiences with Reloader 15 and a 260gr nosler partition

With my 300 win mag I use imr 4831 and a barns 180 gr tsx same as Danny

H1000 pushing a 178 gr ELDX in my 300 win mag. Shew doggy...

I’m shooting a 180gr Berger elite hunter with 71.5 grains of h4831, 300win mag