Need some advice from members. I shot buffalo last year with multiple 375 and 470. Thru lungs and heart but came behind us and ran over 110 yds. Loading for a 505 now. Thinking Barnes 525 tsx at about 2500 cause flat shooting for bigger longer distance plains and less kick. Others I see use barnes 570 or 600. What bullet, powder, grains powder, do you recommend, inducing for best accuracy?

There is nothing mild or "less kick" with any 525gr bullet at 2500fps...great buff round using the TSX or a Woodie weldcore soft.
You can search the BigBore thread for loads.

Suggest that you slow that load down to about 2,300 fps. Even 2,100 fps will get you great results with the 525 TSX in a 505 Gibbs.
Many good loads shown in prior treads.
My personal favorite powder for this case and bullet is H-4831.
Start at about 120 grains of powder. You should reach 2,300 at about 130 - 133 grains.
Use the hottest primer in your kit.
This bullet at 2,300 fps will make more "smack" than the 375 or 470.
Sincerely,

Thanks for the input. I checked the big bore old posts.

I used rl 22 with geat results, check the barnes book, I think I was at 141 grs of powder. It's been 2 years and I don't have my notes handy.

It was a moa load, and I easly broke clay pegions with it at 200 yards.

JD

I use 142gn of AR2209 (H4350) with the 525gn Woodleigh RNSN in my 505 Gibbs. This is with Bertram cases and Federal 215 primers. This load gives me 2500fps. Start at 136gn AR2209 (H4350) and work up from there to be safe. However, I would not recommend that load for buff, it is going 300fps faster than Woodleigh's recommended impact velocity, and will open up very quickly. It is great for smaller game like pigs (devastating in fact), but you won't get enough penetration for buff. Slow it down to 2200fps to get the right balance of expansion & penetration for buffalo. I don't have a load for that velocity, but you would probably need about 130gn AR2213SC (H4831SC), you won't get that low a velocity with a sensible charge of AR2209 (H4350). You may need to experiment or find a suitable load on line. I prefer the 600gn Woodleigh PPSN, so most of my loads were for that projectile. I use 130gn AR2209 (H4350) behind the 600gn Woodleigh for 2270fps, which gives an impact velocity below 2200fps after only 25m from the muzzle. (2200fps is the recommended impact velocity for both the 525gn and 600gn Woodleigh soft points). I don't use less than 128gn of powder because I think it leaves too much air space and potentially causes erratic ignition. I have only tried AR2209 (H4350), AR2213SC (H4831SC) and AR2217 (H1000), and these all work OK at 128gn, but I got some unusual chronograph readings at loads below that and I put it down to erratic ignition due to too much air space. If you use the 525gn Barnes TSX you can drive it faster than the Woodleigh bullets, and still get good results, but you will need to reduce the powder charge. Start at 130gn AR2209 (H4350) and work up from there. I worked up a load for the North Fork 525gn Cup Point, and I got to 2500fps at 134gn AR2209 (H4350). I imagine the 525gn Barnes TSX would be similar. You need to be a bit careful with solid copper bullets as they raise pressures a lot higher than normal jacketed lead bullets.

Thanks appreciate the advice. Interesting for my 505 cases with 215 primers necked down to 375 smks and retumbo powder, one works best at 134 gr and the other at 141 grains