Maby this will put some light on your subject
.257 ROBERTS
Introduced: 1928 Niedner Rifle Co.
1934 (Commercial
Other Names: .257 Remington Roberts
Type: Rimless, Necked, CF
Necked Down 7X57 Mauser
Length: 2.750"
Powder: Nitrocellulose
Primer: Boxer (Lg Rifle)
BULLET:
Type: 1) Expanding-3180 f.s.
2) Hollow Pt-3220 f.s.
3) Expanding-2860 f.s.
4) Hollow Pt-2900 f.s.
5) Hollow Pt-2630 f.s.
Dia: . 2575"
Wgt: 1) 87gr
2) 87gr
3) 100gr
4) 100gr
5) 117gr
CARTRIDGE CASE:
Length: 2.233"
Head to Shoulder: 1.727"
of Shoulder: .19"
Neck : .32"
Base to Neck: 1.911"
Dia Rim: .473"
Base: .472"
Neck: .290"
Shoulder: .429"
Mouth: .290"
Angle of Shoulder: 20@-45'
Pressure: 45,000lb/sq.in.
Bore Dia:
Min: .250"
Max: .2575"
Reload Data:
Billet: Pwdr: grs: MV: ME:
87 4320 42 3310 2112
87 H-380 43 3230 2010
100 4831 47 3032 2040
100 3031 35 2947 1826
117 4530 44 2900 2182 Max
117 4831 45 2870 2140
120 4831 44 2800 2091
125 4350 44 2850 2258 Max
87 FL 3200 1980
100 2900 1870
117 2650 1820
120 2645 1865
The commercial version of this cartridge was made by Remington for their Model 30 bolt-action rifle. It was quickly picked up by Winchester for their Model 54 and later Model 70. The Remington 722 bolt-action and the 760 slide-action models were also available in 257 caliber. Most European-made sporting bolt-action rifles were at one time available for this cartridge. In recent years American manufacturers have discontinued it, although one run of the
Ruger Model 77 bolt-action included some chambered for the 257. The 257 Roberts is based on the 7X57mm Mauser necked-down. Remington changed the original shoulder angle
from 15 to 20 degrees.
ammo is readily available for it. Perhaps not in your local sporting goods store, but if you ask they may get it in for you. Midway has .257R in stock in +P 100, 115, 117 & 120gr boattail/spires, Remington CoreLokt, etc. There are some that have been concerned about .257R drying up for over 25 years and it hasn't happened yet. If you can't get ammo locally Midwayusa stocks plenty
