257 Roberts

RBHarter

West Central AR
I found a load with a Serria 100 grain game king that shoots great , "it's so easy a cave man can do it" . Now I have NOE 260-120 FP and an alloy that has worked well for full power 6.8 Remington SPCII and nominal loads in 222 and 223 while I have no pressure gear I'm sure that the loads are in the mid to high 40 kpsi range and a testament "why didn't I use gas checks years ago....
Back on track .
I've had good results with slow for load powders in reaching best velocities and keeping consistency. The rifle in question is a 95 Mauser and best held under 40 kpsi , in other words perfect for cast mostly . I have data for both H and IMR 4831 and 4350 with some on hand but I also have some W857 that is said to be compatible with H1000 Data . There isn't ,in any of my books, any H1000 data for 257 Roberts but there is for 7x57 ,6.5x55 and 6mm Remington for 168,140 and 100/105 gr jackets . This to me would suggest that if the larger and smaller bore sisters work ,and come in in the mid to upper 40s with jacketed ,then cast should be ok in a middle bore in more or less the same case.
I would feel better if someone had been down this road .....or a parallel side street ,than just being out rooting around with crossed fingers .
The cast bullet hand book doesn't really offer any help as the 4895 to Unique loads offered are held to 1900 fps. It hurts to think about 14 gr of Unique in anything after so many loads of 3-9.5 in pistols besides doubles ,SEE ,myth and the real possibility of bolt set back .
Guidance ,suggestions , slap to the back of the head are all appreciated at this juncture.


I'm not gunning for warp speed just a full case ,minimal ash low pressures and if I get 2500 ,yeah me 2200 will leave me just tickled.
 

yodogsandman

Well-Known Member
I'd post this question over on the CB site due to the larger pool of cast reloaders with possibly real world experience with this.

The Hodgdon website says H1000 is best with magnum sized overbore cases and heavy jacketed bullets. My best guess would be that you couldn't get enough WC857 into the case to cause any pressure problems with cast bullets. If it were me, I'd fill the case to the bottom of the neck, weight the amount, reduce 10% by weight and proceed with extreme caution. That would only be after trying the 4350 or 4831 with published loads and knowing those results.
 

fiver

Well-Known Member
that 6mm rem data would translate.
now if it happens to coincide with the 7mm data and the bullet weights are nominal weights [ie 140grs in the 7, and bout 100 in the 6] your 25 will fall right in line with pressure and velocity in between them.
reducing would be accomplished with a filler, a buffer would speed things up again.

anyway if you want to go slower with less pressure the too slow powders are a good way to do it.
anything slower than RL-25 [about 2 steps slower than rl-22] will get you in there.
 

Ian

Notorious member
It's a bigger case, but the Swedish Mauser does low pressure and high velocity really well with H4831 and buffer to make it burn consistently. If you go as slow a H-1000 you're probably going to need a kicker or a buffer, or at the very least Dacron, to make it clean up at all. Look at it from a "grains of energy" perspective and the rest is about controlling or manipulating the burn speed. If you have starting data for X grains of X4831, use the same grains of slower powder and if you're filling over 80% of the case volume, go load some and shoot over the chronograph, study the soot/mummies in the bore and on the outside of the case neck, and adjust from there.
 

RBHarter

West Central AR
This was my basic train of thought also .
The data for I and H 4831 start at 38 and 39 gr for a 120 jacketed spitzer and come in about 40 kpsi . For the sake of the action I'd like to get into the 30s and I think the W857 (reference H1000 Data) will do that .
I have wandered out in the woods with overly slow powders in small cases but the Mauser family is at that break over point where you can hit the middle pressures with the normally slow and low powders .
Unfortunately the 260-120 FP won't allow for the option of "just using the next weight up data" .
I think this will get me going the right direction safely.
I need to look again and see if there is separated data for the 6mm 105 gr or not. It seems like 6mm , and 7x57 are topped out by space with 4831 .
 

fiver

Well-Known Member
I remember loads using bmg-50 powder in the 7x 57 that hit about 25-2600 fps.
it was pretty much scoop a case full and flick it with your finger type loads.
I don't remember the bullet weight but I'd say it was with 145-150gr.