Reloading Podcast 222 - No Dummy, your finger doesn't belong there

Hello, and welcome to the Reloading Podcast here on the Firearms Radio Network.  

Tonight the guys are talking about the Bob, some questions about consistency.

Cartridge corner: .257 Roberts Cartridge


.257 Roberts

Type Rifle

Place of origin United States

Production history

Designer Ned Roberts

Designed 1920s

Manufacturer Remington Arms

Produced 1934-Present

Variants .257 Roberts (+P), .257 Roberts Ackley Improved

Specifications

Parent case 7×57mm Mauser

Case type rimless bottlenecked

Bullet diameter .257 in (6.5 mm)

Neck diameter .290 in (7.4 mm)

Shoulder diameter .430 in (10.9 mm)

Base diameter .472 in (12.0 mm)

Rim diameter .473 in (12.0 mm)

Case length 2.233 in (56.7 mm)

Overall length 2.775 in (70.5 mm)

Rifling twist 1-10"

Primer type large rifle

Ballistic performance

Bullet mass/type Velocity Energy

75 gr (5 g) HP 3,450 ft/s (1,050 m/s) 1,983 ft⋅lbf (2,689 J)

100 gr (6 g) B-TIP 3,020 ft/s (920 m/s) 2,025 ft⋅lbf (2,746 J)

117 gr (8 g) SPBT 2,840 ft/s (870 m/s) 2,096 ft⋅lbf (2,842 J)

Test barrel length: 24

Source(s): Accurate Powders [1]


The .257 Roberts also known as .257 Bob [2] is a medium-powered .25 caliber cartridge. It has been described as the best compromise between the low recoil and flat trajectory of smaller calibers such as the .22 and 6mm, and the strong energy but not the strong recoil of larger popular hunting calibers, such as the 7mm family and the popular .30-06.[3]


Many cartridge designers in the 1920s were creating various .25 caliber cartridges. Because of its size, the 7×57mm Mauser case was a common choice, having near the ideal volume capacity for the "quarter-bore" (called this because the .25 caliber is one quarter of an inch) using powders available at that time. Ned Roberts is usually credited with being the designer for this cartridge idea. Eventually in 1934 Remington Arms chose to introduce their own commercial version of such a cartridge, and although it wasn't the exact dimensions of the wildcat made by Roberts, they called it the .257 Roberts.[4]


From its introduction until the appearance of more popular 6 mm cartridges such as .243 Winchester and 6mm Remington, it was a very popular general purpose cartridge.[5] Today, although overshadowed by other cartridges, it lives on with bolt-action rifles being available from some major manufacturers.


https://www.ballisticstudies.com/Knowledgebase/.257+Roberts.html



  1. My story of how to be a Dumbass. By Rusty S.

    1- Get up pour coffee and sit down to reload.
    2- Make sure dies are correctly adjusted
    3- Load freshly prepped 30-06 case in RCBS press.
    4- Make sure dies are correctly adjusted again.
    5- With left hand pointer finger reach up into underside of die to make sure decapping pin is correctly adjusted.
    6- Simultaneously with right hand pull down on ram lever running a nice shiny case into left hand pointer finger; cutting a perfect half moon into the finger!

    My suggestion is NOT to do this…

  2. Jason Posted:
    During the cartridge sizing phase I’m noticing some inconsistencies with the results. After each pull on a 30+ year old RCBS manual loader my sizes vary from .001 to .006 from the desired length. I can never seem to get the length to be consistent after each throw. This is happening with both pistol and rifle, old and new dies. After a decade of having these same results I can say I’ve never had an issue at the range or cartridge feeding. -- So, is this normal for a manual loader? Should I have any concerns or is this acceptable and others see the same results?

  3. Derrick posted:
    What is your starting load for 250 gr Keith style SWC using Alliant 2400? Alliant calls for 20 grains and if I deduct 10% as a starting load that would be 18 grains. Seems a little hot to me for cast…

  4. Raymond posted:
    I was wondering if anyone knows how to figure out my proper bullet seating depth for my bolt gun .308 win? I know what my book says for COL, but I've heard of people figuring out a way that is rifle specific?







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