I have fireformed 100 cases.
From the formed cases, I have only shot 6 rounds of 87 gr Berger moly 47.3 gr IMR4895 and got the first 1" group of my life

For load books, I have the Sierra, Hornady, Accurate Arms, and both the early hot Speer and late [1974] wimpy load books.

For coated bullets I have; 72 gr, 87 gr, 100 gr, 115 gr, and 117 gr.

For powders I have; XMP5744, RL-7, H335, IMR4895, RL-15, Varget, H414, IMR4350, and H4831SC.

The rifle is a VZ 24 action with Lothar Waltar light varmint barrel.

What loads do you like?

I favor AA 3100 in this one with 100-120 grain bullets. AA 3100 is the about the same thing as IMR 4831. Figger 50 grains for max with 100 grainers and about 48 with 115-120s.

The old H-4831 was a little bulky. The SC might work better, but I have never used it.

Your 4350 is an excellent bet for the heavier bullets. 47 grains of it gave me excellent results under the 115 Nosler Partition.

IMR 4320 is what I used with the lighter bullets. 75 grain Sierra gave me excellent accuracy with this powder.

I'm not up on the newer powders but I would not use anything faster than 4320.

Im still waiting for mine but Id sure be interested in your findings.

Here are some favorable looking loads from P.O. Ackleys Vol II.

100 grn bullets
4350 (no brand designation, Im assuming IMR..??)

48 grs-2930
52 grs-3315

120 grn bullets

4831
48 grs-2615
50-2780
52-2900

4350
45-2720
47-2805

(usual start low disclaimer here..!)

Some of Mr. Ackley's data is hot. I'd stick with current load manuals for data sources. My 2 pennies worth.

Clark, try 50gr of IMR 4350 with 100gr bullet with WInchester cases. This is a pretty classic load for the 257 Ackley.
My Ackley likes about all the brands of 100gr bullets except the new 100gr Nosler Partitions, but it shoots the old screw turned 100gr Nosler Partitions like they were match bullets. I still have about 10 of these bullets left and I have them horded away for some special hunt somewhere down the road.
My favorate hunting load right now is
100gr Barnes X bullet with 53gr of Reloader 22, Winchester cases and winchester large rifle primers. It clocks at 3400 fps in my rifle.
This is a max load, so work up to it slowly.
I really like Reloader 22. It is just as accurate as 4350, but it gives higher velocities. I have been told that Norma MRP powder is real good,but it is hard to get in my neck of the woods so I have not tried it yet.
I hope you enjoy your 257 Ackley half as much as I do mine.
Dale