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Bear with me while I ramble through some of this. I promise to eventually get to the part where the rifle goes boom and I measure the holes in the target. I like firearms, so the research interests me and, sometimes, the information acquired makes it to the page… where it gets in the way of the pictures.
 
When Remington homologated the 257 Roberts, the original Roberts’ design was altered. The case shoulders were sharpened from 15º to 21º, which: made the case a straight neck down of the 7x57mm cartridge1, reduced production tooling investment and provided an improved surface for more positive headspacing. It also prevented chambering the Remington sanctioned round in earlier custom firearms marked for the same cartridge.
 
No, I don’t think Remington was hatching a nefarious plot. I think it was Remington’s acknowledgement that, in those days, wildcat cartridge dimensions tended to follow the preferences of whomever made the chamber reamer, so they needed to shied their customers from the possibility of sticking an almost right cartridge into an almost wrong chamber. I have read that Remington changed the cartridge but retained the name to pay homage to Roberts. It might also have something to do with getting some winds in the cartridge’s sails from a decade of preexisting good will. So I had this great little Ruger M77 and some boxes of factory ammo…
 
Factory ammo performance
 
SAAMI references two Maximum Average Pressure specifications for the 257 Roberts; standard @ 54,000 PSI and +P at 58,000 PSI. Both are currently produced with a ballistic differences that are notable. As an example, standard pressure Remington Express ammunition is rated at 2,650 fps of muzzle velocity and 1,824 ft-lbs of muzzle energy while Winchester Super X +P is rated at 2,780 fps of muzzle energy and 2,009 ft-lbs of muzzle energy. Both ratings are based upon a 24″ test barrel standard. Reviewing published specifications from other manufacturer, this difference between the two types of loadings is fairly consistent.
 

+P Cartridges

Weight
Grains
Bullet Type MV
24″
Rated
MV
22″
Actual
Δ
Nosler Custom 110 AccuBond 3000 2933 -67
Hornady Superformance 117 SST 2945 2836 -109
Winchester Super X 117 Power Point 2780 2735 -45
Federal Premium 120 Partition 2800 2675 -125
 
The barrel length comparison can be used for whatever it might infer as a relative indicator, however, it is an apple to bicycle chain comparison as these are rated 24″ numbers and not recorded live fire.
 

What would that look like… if I could see small things far away?

 

Nosler Custom 110 Grain AccuBond
Yards 0 50 100 150 200 250 300
Velocity – fps 2933 2820 2710 2602 2497 2394 2294
Energy – ft.-lbs. 2101 1942 1793 1653 1522 1400 1285
Momentum – lbs-sec 1.43 1.37 1.32 1.27 1.22 1.17 1.12
Path – in. -1.5 0.5 1.4 1.2 -0.3 -3.3 -7.7

Max Ordinate 3″
Point Blank Range 215 Yards

 

Hornady 117 Grain SST

Yards

0

50

100

150

200

250

300

Velocity – fps

2836

2717

2602

2489

2380

2273

2169

Energy – ft.-lbs.

2089

1918

1758

1609

1471

1342

1222

Momentum – lbs-sec

1.47

1.41

1.35

1.29

1.23

1.18

1.12

Path – in.

-1.5

0.6

1.5

1.1

-0.7

-4.0

-9.1

Max Ordinate 3″
Point Blank Range  214 Yards

 

Winchester 117 Grain Round Nose
Yards 0 50 100 150 200 250 300
Velocity – fps 2735 2553 2379 2212 2052 1899 1754
Energy –
ft.-lbs.
1943 1693 1470 1271 1094 937 799
Momentum – lbs-sec 1.42 1.32 1.23 1.15 1.06 0.98 0.91
Path –
in.
-1.5 0.7 1.5 0.8 -1.7 -6.3 -13.2

Max Ordinate 3″
Point Blank Range 197 Yards

 

Federal 120 Grain Nosler Partition

Range

0

50

100

150

200

250

300

Velocity – fps

2675

2563

2454

2347

2243

2142

2044

Energy – ft.-lbs.

1906

1750

1604

1467

1341

1223

1113

Momentum – lbs-sec

1.42

1.36

1.30

1.25

1.19

1.14

1.09

Path – in.

-1.5

0.7

1.5

0.9

-1.3

-5.2

-11.0

Max Ordinate 3″
Point Blank Range 203 Yards

 

I’m not sure who at Winchester should be thanked for the round nose bullet. There are plenty of spire types in that weight range that Winchester could have loaded. Perhaps it is a hold over from Winchester producing a round nose for the old 25-35 WCF and lever action rifles? It is also a way to get to a heavy bullet by thickening its ogive without adding bullet length… or… or… it be a hold over to the old brush buster notion of round nose bullets.

Anecdotal support of the latter –  Hornady’s Eight Edition reloading Manual, under 25-35 WCF data there is a comment about the 117 grain round nose bullet. “…our 117 grain Round Nose, a very deadly game bullet preferred for hunting brush and a bullet that will expand easily even at low remaining velocities.”. It is rated for 2000 to 3300 fps MV in their bullet listings… which is actually the same as all of their other 100+ grain 0.257″ bullets. Oddly, the same bullet is listed for the Roberts and Roberts AI without comment. Anyway…

 

Almost had a 4×4 picture….

 

Cold or hot barrel, the Ruger M77 Hawkeye put up the same group sizes within an ammunition type. From a steady rest and through a substantial scope: 1) Nosler 1/2″, 2) Hornady 1 5/8″, Winchester 1/2″, Federal 1″. If there was a shocker here for me it would be that ugly flying frying pan of a Winchester bullet.

 

 
No, I don’t know what’s up with the Superformance ammo and, no, I don’t think that is typical of the product as I have considerable experience with it delivering excellent accuracy. Maybe it’s just this cartridge and this rifle’s barrel harmonics? There are results here that are just… well
 
Personality
 
For as mundane as the name “Roberts” may make this cartridge sound, as opposed to,,, Fireball or Ultra, it is anything but. Recoil is modest, as is muzzle rise, but the combination has a sharp… bark. And why not? It has about the same case capacity as a 308 Winchester hot rodded down to 25 caliber.
 
Very nice rifle, very balanced combination with a lot of versatility. All things preferable in a hunting rifle. For more information, check in at Ruger.Com.
 
1) The Handloader’s Manual of Cartridge Conversions – Donnelly & Handbook for Shooters and Reloaders – Ackley