Doing a new build...Why not 257 Roberts?

[mauser284]

Now that we finialy have long sleek heavy for bore .257 bullets the 25-06AI with something like 134gr. bullet is a game changer now in 2025. 1:7 twist barrel. Probably looking at 3100fps to 3200. To get any faster you would have to step up to a Weatherby and burn a ton more powder. As much as I like the 257 Roberts it can not compete with the 25-06AI with a 134gr. bullet and modern powders. I doubt the 6.5PRC can do much better to be honest!

It has only taken the industry 36 years to give me what I want in a .257 bullet.

257 Bob AI just seems like a lot of work.

If you wanted to hit the easy the button as much as I hate to say it the 25CM would be my second choice after the 25-06AI. 25CM has plenty of available brass. I am not a fan of NRL but we can thank those guys and gals for breathing new life into the .257 and getting idiotic industry to finaly give us the .257 bullets a lot of us have wanted for close to 40 years!

 

[Infrequent Shooter]

You can make it from .30-06, but it's more work. This is 7x57mm I made from Lapua. I've gone another step down to .257 Roberts, but neck turning is advisable.

View attachment 1526813View attachment 1526814

I know this is probably described many places on the internet... would you mind telling your process, dies and order to get to 7x57?

 

[Adam in WI]

I just used a regular FL 7x57 die with the expander removed. I think I used imperial sizing wax. If I remember right, 7x57 was ok to trim and simply resize. The .257 Roberts required neck turning. Obviously your own measurements would dictate turning or not.

 

[papa]

My favorite rifle is a Win. 70 in .257AI. A tack driver and deadly on deer size and smaller game/critters.

 

[bobcat93]

25 creed is more efficient case , and i believe beats out the 257 Robert wiith the 100gr sierra match kings

 

[Cloudrepair]

I am wanting to do a 257 roberts AI now were to get a reamer ? Im going to put it in a vz24 mauser to go next to its brother a 7x57 mauser in the same rifle only that one is all factory original.

 

[Infrequent Shooter]

Ackley ‘Bob running a 3.220” COAL on a Defiance XM. 1st photo is bunch of cartridges with the (now defunct) Blackjack 131 bullet stuffed in. 2nd photo is the long Ackley been 2 factory Hornady rounds in .257 Rob. I run a 1:7.5t barrel and it has no problem between 100-135gr bullets.

I also have a 25x47L, but if I had it to do over and would actually own something chambered in a Creedmoor, the 25CM is about the closest thing to a unicorn cartridge I’ve seen.

To the OP:
For lighter bullets and varminting, that 25BR should be a fun setup. Enjoy!

SD, would you still pick 25CM?

 

[SweaterDood]

SD, would you still pick 25CM?

If I had to pick 1 cartridge and live with it, and it was a .257 cal cartridge, and I overcame my insecurities that make me refuse to own any sort of Creedmoor…. Yes.

I am wanting to do a 257 roberts AI now were to get a reamer ? Im going to put it in a vz24 mauser to go next to its brother a 7x57 mauser in the same rifle only that one is all factory original.

Manson or JGS reamers. Be sure to tell them which brass you plan to use and if possible measure the web diameter (approx .200” fwd of the case head) the .257 AI has a lot of reamer variations based on differing brass dimensions and is prone to case head separation if you don’t do this.

 

[Rubberduckie]

I had alex wheeler chamber a barrel for a defiance action in 257 roberts. I got a bunch of norma brass from raven rocks. So far it shoots beautifully. It seems to like the 110 grain sierra bullets. I t will be a finalist if I start selling my stash.

 

[SweaterDood]

I know this is probably described many places on the internet... would you mind telling your process, dies and order to get to 7x57?

I ended up having to make my .257 AI from Lapua 8x57 IS, which is very close to 30-06, but slightly larger web diameter. Here is what I did:
- Drill and Flame anneal each case neck (if I had access to the AMP and wildcat settings would have saved a couple days worth of work)
- .308 busing die (size down approx .020” a time. Trim, Re-anneal, & re-lube between sizings)
- Mandrel up to .25 cal for neck turning
- Turn necks to .015” thick (not final thickness)
- Re-Lube & Finish sizing with a .257 Rob FL die (not bushing, I bought a Lee set just for this step & factory crimp). You want a snug fit in the chamber for fireforming. This is standard for an Improved case, but when doing this much work to the brass, I highly advise it on a standard case for brass life.
- Mandrel again
- Final Turning of necks to .012-.013”, kissing the shoulder
- Fireform with a moderate charge.
- Clean up necks at .012”, kissing the shoulder once more. Done

7x57 would probably be easily achievable with just a 7x57 bushing die, but will still require trimming and neck turning.

It’s a LOT of work and was the only way to get decent brass to truly fit my chamber. I WILL NOT go to these lengths again for ANY cartridge in the future. Total PITA. 2/10 only worth the knowledge and experience gained. That barrel/chamber taught me a truckload of hard lessons. Fortunately, its been an absolute hammer.

 

[Infrequent Shooter]

I ended up having to make my .257 AI from Lapua 8x57 IS, which is very close to 30-06, but slightly larger web diameter. Here is what I did:
- Drill and Flame anneal each case neck (if I had access to the AMP and wildcat settings would have saved a couple days worth of work)
- .308 busing die (size down approx .020” a time. Trim, Re-anneal, & re-lube between sizings)
- Mandrel up to .25 cal for neck turning
- Turn necks to .015” thick (not final thickness)
- Re-Lube & Finish sizing with a .257 Rob FL die (not bushing, I bought a Lee set just for this step & factory crimp). You want a snug fit in the chamber for fireforming. This is standard for an Improved case, but when doing this much work to the brass, I highly advise it on a standard case for brass life.
- Mandrel again
- Final Turning of necks to .012-.013”, kissing the shoulder
- Fireform with a moderate charge.
- Clean up necks at .012”, kissing the shoulder once more. Done

7x57 would probably be easily achievable with just a 7x57 bushing die, but will still require trimming and neck turning.

It’s a LOT of work and was the only way to get decent brass to truly fit my chamber. I WILL NOT go to these lengths again for ANY cartridge in the future. Total PITA. 2/10 only worth the knowledge and experience gained. That barrel/chamber taught me a truckload of hard lessons. Fortunately, its been an absolute hammer.

big thanks, great report.

 

[GetReal]

Cuz Im outta money.

 

[ebb]

Toasty the OP posted in March of 2024 he had a barrel on the way. I was hoping to see a range report by now? Do you think it shoots so well he is reluctant to share the results?

 

[SeabeeKen]

My 257AI is a tack driver and slams deer with a barnes 80 gr ttsx at 3300. This past season it took 2 does with 1 shot, fully penetrating both.
A 75 gr hammer runs 3400 max
Im using jamison 257 robts brass but have some ppu 7x57 necked down whenever the jamison is done.

 

[Webphut]

While you are all talking all the other 25's, I been thinking Sako AV in 25-06 for some time. Something about the elegance of high gloss blue with wood stocks. just me I suppose.

 

[ISS]

I have a 25-284 Rockchuck rifle. Think 25-06 velocity in a short action...

 

[karrarararararar]

I have a buddy that built a 257 Roberts prone gun shooting the heavy Bergers. He absolutely loves it, but does admit 25 Creedmoor is the easier button due to brass

 

[Ackman]

Picked up a really nice new bench stock and have a savage action laying around. Looking to do a new build. Primary use of the new build is long range paper punching 500-1000 yards and prairie doggin. Going on a rifle that will weigh 12 to 14 lbs to keep recoil low enough to see hits. Looking for something with enough accuracy and weight to easily confirm hits at 600 yards on varmints. Already shoot a 6br and several smaller chambers and have 260 Rem that is not a great shooter with varmint bullets I have tried out of it. Thinking about a 257 Roberts. Ballistics with 90gr SBK (wind drift) is better than varmint bullets I am shooting with my 6br. The other chamber I was considering is a 25br, but having a hard time finding a barrel maker that offers that in a savage prefit. Any comments or suggestions on accuracy of this cartridge, ease of finding brass, bullets, etc? Feel free to offer suggestions on another short action caliber that may work better.

Years ago I used a 257AI on rockchucks. Brass was Win. and Frontier. Speer 87gr TNT's, never chrono'd the load, but it was effective. Turned 'em into an unrecognizable pile of fur and guts. Those TNT's shoot well. It's not really a prairie dog cartridge though, there's much better for them. Since youve been doing 6's, do another one, a 6BRX. A step up in velocity and an easy fireform. In fact, even fireforming loads are just unbelievably accurate, same velocity as the dasher and use your BR dies on the finished product.

 

[Oso]

Hornady Podcast recently did episode on 257 Roberts. The 257AI seems to be better 40degree shoulder vs original 15 degree shoulder.

 

[sofarfrome]

Take it a step further and chamber in 257AI. I built one some time back on a trued Rem700 with a Shilen SM barrel. Bugholes at 100 yards and remarkably accurate out to 600.