What would be my bullet choices for a 100 grn traveling at over 4000 FPS.

What powder would be my best choice?

Savage action, 28" Pac-Nor 5 groove 10" twist barrel. Shooting at whitetail, varmints and hogs.

Am looking at as economical a load as possible, so that I can shoot more and keep the barrel manufactures in business. But need a bullet that will hold together at impact.

Your into a serious velocity domain, one I've never been in with a 25 caliber. My favorite 100 grain 25 cal bulet is the Nosler Partition.
I would try them as they are very well made, and might hold up at 4K fps.

You have a flat shooting rifle, for sure.

Don

I've checked with Quickload 3.3 and IMO, it will be hard and risky for you to get "over 4000 FPS" with any available powder and with any 100 gr bullet. It's just a guess, of course.

I've found surplus WC 872 to be excellent with "overbore capacity" cartridges. It is something in the neighborhood of 15% slower (whatever that may mean) than H870/AA8700. You can typically use the maximum loads listed for those powders as a starting place with WC 872. CAUTION: Surplus powders can and do vary. Use this powder only if you are experenced in working up loads with powder/bullet/cartridge combinations that are out of the ordinary.

HOWEVER, I seriously doubt your being able to boost a 100 grain .257 bullet to 4000 fps, even with the STW case and the slowest of powders, at least not with a case life of more than a shot or two. If your extra long barrel is also extra slick, it might happen.

Google an article about what they call the .257 hot tamale. Its a .257 stw.http://www.gunhuntermag.com/Features/030818Tamale.html

I've read that article and it is the one that got me thinking of this project. The Lost River Bullets (J-36) are about $27 for 20. Looking for another option?

I've never had much luck with the 100's, I use 115 Nosler BT with great results. Reloader 22 has worked well also.

Barnes TSX and RL 25 would be a good place to start.

I built one for a customer a year ago or so. We never could break more than 3950 with a 100 grainer, and that was with plenty of pressure! I would go with the heavest bullet you can find to get any sort of efficency from it. RL22 was the best powder we found. RL25 made more pressure and less speed. Extremly overbore cartridges do some very strange things. I had the same problems with a 22/6mm Ackley.
The 257STW is a little too much of a good thing.
My customer eventualy became frustrated with it and traded it off.

Swd, I know I know over-overbore but I still am going to get a new barrel and work up the best load I can get. May make 4K may not. But it will push a .25 bullet pretty fast and pretty flat.

With the donnar action being a Savage it will be an easy barrel swap between the 257 STW and the 7mm STW. May even make a 270 stw, but I doubt it when I could just put a 120 grn .284 bullet in the 7mm.

I used the old 90 XBT and either RE-22 or RE-25. As SWD says these rounds can do strange things..............I could never get 4 grand, but it was a blast

And consider the 6.5 STW Better for powder and more versatile IMO.

My experience has been that large cases are best with heavy for calibre bullets.

Also, if wind is a constant problem,(as here in South Oz) then heavy high BC bullets are better than using lighter bullets at the longer ranges.

I currently have a 25/06AI with a 24 inch Shilen 10 twist barrel that will stabilise and shoot accurately bullets ranging from 100 grain Nosler BT up to and including the Wildcat 125ULD and the Wildcat 130 FBBCHP.

I also have a 257W with a 26 inch Krieger 7 twist barrel, that will stabilise and shoot accurately the Wildcat 156 grain ULD. (1.550 inches)

I recently discovered that the 125 grain wildcat ULD, and Nosler 115 BT held together despite the 340,000 - 350,000 rpm generated, so I have the flexibility to use the lighter bullets if I want to. Good luck in your project, Brian.

Harold, you might consider a modified STW with the shoulder pushed back maybe .100" or so. I bet it would make the same or more speed with a little less case capacity. The big problem with the 257STW is we never could get more than about 80% capicity before getting lots of pressure. Slightly less capacity might actualy burn more powder rather than just blow it out the muzzle. Just some food for thought from somone who's already been there a few times.