Skip to main content

.257 Ackley Improved Ammo

You can easily fireform 257 Roberts factory brass or loaded rounds to achieve the .257 Ackley Improved case shape.

.257 Ackley Improved Ammo
By his own admission, P.O. Ackley considered the .257 Ackley Improved to most likely be his best wildcat.

A few issues back, two Shooting Times readers expressed interest in reading about wildcat cartridges and the adventurous experimenters who created them. Coincidentally, I had just embarked on my most recent handloading project with the interesting .257 Roberts Ackley Improved wildcat.

According to P.O. Ackley, the modified 257 Roberts was likely the best improved round compared with the couple dozen or so factory cartridges he’d experimented with Ackley’s signature case modifications included reducing the body taper and increasing the shoulder angle—both significantly!

However, an even more important feature of the typical Ackley Improved (AI) wildcat is that he maintained the shoulder headspace datum of the parent factory round. That allows you to safely fire factory cartridges in the modified chamber. It also means you can easily fireform .257 Roberts factory brass or loaded rounds to achieve the .257 AI case shape, so you don’t need expensive forming dies or go through extensive case-forming steps.

Ned H. Roberts was one of several handloaders who experimented with wildcat cartridges in the 1920s and ’30s. He chose the 7x57mm Mauser case to modify and, reportedly, tested myriad configurations before settling on the “perfect” .25-caliber varmint and deer cartridge. Early articles by Townsend Whelen and Jack O’Connor proclaimed the virtues of the .257 Roberts in the hunting fields. Many hunting and reloading articles fondly referred to Ned Roberts’s wildcat as the “.257 Bob.”


When Remington decided to adopt it as a factory cartridge in 1934, the company made a few minor dimensional changes to preclude firing factory ammo in rifles chambered for the wildcat round. Remington paid homage to the inventor by naming the new factory round the .257 Remington Roberts. The Remington part of the moniker was eventually dropped.


The current SAAMI spec for the .257 Roberts Maximum Average Pressure (MAP) is 54,000 psi. Winchester introduced a +P version with a MAP of 58,000 psi in the mid-1980s. That’s still less than the typical 60,000 to 65,000 psi of comparable modern rifle cartridges.

The .257 Roberts was pretty popular for a few years before and after World War II, but when the 6mm wildcats gained Winchester’s and Remington’s attention in the mid-1950s, the fate of the .257 Roberts was sealed. Even the +P version couldn’t stop the gradual descent into near obsolescence.

257-Roberts-Ackley-Improved

An Accidental Endeavor

I embarked on my .257 AI project almost by accident. While thinning out my firearms inventory, I realized I could convert my Ruger Hawkeye bolt-action rifle chambered for .257 Roberts to .257 AI. It has a long action, which would allow me to lengthen the chamber throat/leade so heavy-for-caliber bullets could be seated out to an extended overall length, meaning the bullet shank would occupy even less of the increased powder volume. Later, when I measured water capacities of a standard .257 Roberts case and several fireformed AI cases, the difference was about 13 percent (60 grains compared to 53 grains of water).


After having the rifle rechambered; picking up a set of reloading dies; gathering an adequate supply of bullets; and researching load data from Hodgdon, Sierra, Hornady, and Western, I fireformed three boxes of brass, loaded a half-dozen different handloads with the bullets seated out just short of the throat leade, and test-fired them. I was pleased with the ballistics, and I lost only one case. Plus, the primer pockets are still tight after at least three firings. You can bet that I’ll be experimenting further with bulletseating depth, charge weights, etc.

I want to make readers aware of one special step that’s required when handloading the .257 AI. You must anneal the case neck/shoulder to ensure maximum case life. Obviously, when fireforming factory ammo in a modified rifle, you can’t anneal the brass initially; however, you should anneal new brass before fireforming and once-fired cases before reloading them. I followed Nosler’s instructions shown in its No. 8 reloading manual and achieved excellent results.

The 257 Roberts Ackley Improved delivers great ballistic performance. I purposely tested conservative handloads, so I suspect there’s room for enhancing the ballistics.


GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

See More Recommendations

Popular Videos

The Future Of Special Operations Small Arms

The Future Of Special Operations Small Arms

We're taking a look at what the Army's Elite Units are using for service rifles and what the future of SOCOM sniping looks like.

Skills Drills: 3-Second Headshot

Skills Drills: 3-Second Headshot

James Tarr runs through the 3-Second Headshot drill.

Black Hills Evolution of Rifle Cartridge: .308 Win. 175 Gr. Match

Black Hills Evolution of Rifle Cartridge: .308 Win. 175 Gr. Match

David Fortier talks with Jeff Hoffman of Black Hills Ammunition about the evolution of the .308 Win. 175 Gr. Match bullet.

Tactical Solutions Introduces New X-Ring Takedown SBR Rifle

Tactical Solutions Introduces New X-Ring Takedown SBR Rifle

Keith Feeley of Tactical Solutions sat down with Michael Bane at SHOT Show 2018 to talk about the new X-Ring Takedown SBR .22LR rifle.

See More Popular Videos

Trending Articles

Improved bullet ballistic coefficients lead to greater performance and accuracy downrange without upping blast and recoil. Here's why.Improved Ballistics a Key to Accurate Long-Range Shooting How-To

Improved Ballistics a Key to Accurate Long-Range Shooting

Rick Jamison

Improved bullet ballistic coefficients lead to greater performance and accuracy downrange...

The .30-06 Hawkeye Hunter features a 22-inch stainless-steel barrel and a satin-finished walnut stock. Magazine capacity is four rounds. It is well made, accurate, and attractive. This is a fine rifle that is light enough to tote over hill and dale but heavy enough to hold steady for precise shooting in the field.Ruger Hawkeye Hunter .30-06 Review Rifles

Ruger Hawkeye Hunter .30-06 Review

Steve Gash - August 17, 2020

The .30-06 Hawkeye Hunter features a 22-inch stainless-steel barrel and a satin-finished...

Shooting Times editor Joel Hutchcroft provides a comprehensive list of ideal Father's Day gifts.Shooting Times Father's Day 2019 Gift Guide Accessories

Shooting Times Father's Day 2019 Gift Guide

Joel J. Hutchcroft - May 07, 2019

Shooting Times editor Joel Hutchcroft provides a comprehensive list of ideal Father's Day...

The new Winchester Active Duty 9mm ammo is loaded to the same military ballistics specifications as for the MHS program and has a rated muzzle velocity of 1,320 fps and a muzzle energy of 445 ft-lbs.Winchester Active Duty 9mm Ammo Review Ammo

Winchester Active Duty 9mm Ammo Review

Jake Edmondson - July 17, 2020

The new Winchester Active Duty 9mm ammo is loaded to the same military ballistics...

See More Trending Articles

More Reloading

Because case prep is the most time-consuming step in the handloading process, we say any tool that makes it easier is a bargain.Case Prep Made Easy Reloading

Case Prep Made Easy

Lane Pearce - May 29, 2020

Because case prep is the most time-consuming step in the handloading process, we say any tool...

For plinking, target shooting, and routine personal-defense needs, you owe it to yourself to try Berry's plated handgun bullets.Loading Berry's Plated Handgun Bullets Reloading

Loading Berry's Plated Handgun Bullets

Lane Pearce - August 03, 2020

For plinking, target shooting, and routine personal-defense needs, you owe it to yourself to...

Starting the handloading process with clean brass allows the cases to be better inspected, and that enhances safety as well as the loads' performance.Reloading Tip — Start With Clean Brass Reloading

Reloading Tip — Start With Clean Brass

Lane Pearce - September 18, 2020

Starting the handloading process with clean brass allows the cases to be better inspected, and...

Handloading the .38 WCF is a bit more involved than handloading for other cartridges, but Reloading .38 WCF for Rifles Reloading

Reloading .38 WCF for Rifles

Lane Pearce - July 22, 2020

Handloading the .38 WCF is a bit more involved than handloading for other cartridges, but...

See More Reloading

Magazine Cover

GET THE MAGAZINE Subscribe & Save

Digital Now Included!

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW THIS MONTH'S ISSUE Arrow

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Phone Icon

Get Digital Access.

All Shooting Times subscribers now have digital access to their magazine content. This means you have the option to read your magazine on most popular phones and tablets.

To get started, click the link below to visit mymagnow.com and learn how to access your digital magazine.

Get Digital Access

Not a Subscriber?
Subscribe Now