I looked in my books and almost all the .257 Roberts cast loads were for gas check designs and way over your limit of 1400 fps, but”¦
From Why Not Load Your Own!, Townsend Whelen:
Ideal (Lyman 257464) 97 grs. - 14.0 - SR4759 - 1850 fps
Ideal (Lyman 257464) 90 grs. - 19 to 22 - IMR4198 - Powder charge “depending on size of case"
Bond F-257730 89.0 grs - 12 to 14 - SR4759
From Practical Dope on the Big Bores, F.C. Ness:
.25 High-Power Special (.30-'06 necked down to .25 caliber)
"The squirrel load was 5 grains weight Unique or about 10 grains No. 80 behind .258-inch lead-alloy bullets of 86 to 110 grains weight, or at velocities between 1250 and 1500 f.s."
"That octogenarian, U.S. Hubbell, of Tensleep, Wyoming, who has had 60 years of shooting experience, calls the .257 Roberts, “King of the Rifle Family", because it does so well with 7, 9, 10, 12, and 14 grains of No. 80 or No. 2400 powder behind gas-check bullets weighing 65, 80, 85, 94, 100, and 111 grains, and also serves for such big game as elk and bear. ”¦In the Ackley .257 Roberts he used the 100-grain Ideal gas-check No. 257418 and 16.5 grains of 2400."
"One load in the .257 Roberts was 19 grains of No. 2400 powder behind the Ideal gas check bullet No. 257418 (100 grains) and the impacts were 1¼ inches high at 100 yards and 36½ inches low at 300 yards; three were 36½, 37¼ and 38 inches low."
"As a further check, Hubbell did some more shooting with 19 grains of No. 2400 behind an 85-grain bullet (No. 257312) with the zero impact an inch high at 100 yards. At 300 yards the five shots landed low by 35, 36, 37, 41, and 39 inches, he says, adding that all shooting was done from bench rest with muzzle and elbow support.”
” Phillip Newcomb, of Manchester, Conn., reports find a good accurate load gas-check load with the same powder for the same cartridge. He used the Ideal 65-grain .25-20 bullet cast hollow point. He found it difficult to make uniform noses because the pin could not be kept sufficiently hot, and he had to cull out those with the most perfect points for his test. Using the W.R.A. No. 115 primer he tried two loads, above and below Hubbell's charge, shooting prone with sling at 100 yards.
” The heavier load was 20 grains of No. 2400 and Newcomb estimated it gave about 2600 f.s. It grouped well, but about one flier in every five shots enlarged the groups to 3 inches. He considered entirely satisfactory for chuck shooting up to 150 yards, and it left only a trace of easily removed leading in the bore, but he elected the lighter 15-grain load for his field shooting. This load (2100 f.s. estimated) gave 1½-inch groups, including the first fouler from a cold barrel”¦"
"The 15-grain powder charge also was the best one for the Ideal 100-grain pointed gas check bullet which has been a pet problem of Newcomb's because of the inconsistent results he had obtained with it, groups ranging from perfect accuracy to 5 inches spread at 100 yards. Because the normal group and the fliers increased as the shooting progressed he assumed inadequate lubrication was responsible, which led to oiling each bullet just before firing when the normal groups consistently stayed with 1½ inches so lubricated or treated."
"Another Newcomb load is the Ideal plainbase bullet No. 257231 (111 grains) with 13 grains of No. 2400 or 11 to 12 grains of No. 80 powder, the bullet being seated as cast and without neck sizing. This bullet tips somewhat over a range of 200 yards, owing to low velocity and low rate of spin, but he has gotten 10-shot groups as small as an inch and 1½ inches at 200 yards with it and these loads."
"Another fine lead-alloy load which grouped better than factory loads in the .257 Roberts was made with Ideal bullet No. 257283, cast of one part tin to fifteen parts lead. It weighed eighty-five grains. Out in Los Angeles, C.J. Derrick used it with 6.5 grains Unique and the R.A. No. 8½ primer for 1500 f.s.m.v. He lubricated the bullet with a combination of tallow, beeswax, and graphite. He was rewarded with 100-yard groups of from .88 to 1.5 inches. The drop or impact difference between 100 and 200 yards was nine inches."
GAS CHECK LOADS FOR .257 ROBERTS
Loverin 600 Yard Loads (That's what it says in the book.)
20 grs. - 4198 - No. 257616
19 grs. - 4198 - No. 257730
19 grs. - 4227 - No. 257730
22 grs. - 4198 - No. 257312
25 grs. - 3031 - No. 257312
25 grs. - 3031 - No. 257616
Other Loverin Loads (I left out the obsolete powders)
19 grs. - 4198 - No. 257720 H.P.
25 grs. - 3031 - No. 257720 H.P.
20 grs. - 4198 - No. 257720 H.P.
16 grs. - 4227 - No. 257720 H.P.
6 grs. - Unique - No. 257720 H.P.
6 grs. - Unique - No. 257500 H.P.
Soft Game Meat Loads
.250 Savage & .257 Roberts (85-grain lead-alloy)
(1300 f.s.) 8.0 grs. No. 80 or 10.5 grs. No. 4759
In an aside, the book mentions a triplex load of 6.5 grs. of 2400, 6 grains of Lightning and 26.5 grains of IMR4320 with a 115-gr. jacketed bullet. They were brave in the old days”¦