257 Roberts/AI

[BLJ]

Considering doing something with one of these.

Currently have a 257 Roberts on a Mauser 98 action.
Shoots well but it is twisted very slow. 1/14 measured with a cleaning rod.
Always shot 87 Hornadys well, but I’m wanting to try something heavier.

Couple questions.
The 134 ELDM will be heaviest bullet I want to shoot. The other bullet I’m considering is a 120 Partition.
Would a 1/7.5 twist 20” barrel be sufficient for these bullets at 257 Roberts velocity?
What’s lightest bullet that would work with the 7.5 twist? Or do I need to go faster for the heavier bullet?

Right now the Mauser 98 has room for 5 in the mag.
Will I be able to still get 5 in the mag with a 257 Roberts AI?
It seems like there will still be enough room, it haven’t been able to find out for sure.
I’d prefer to go AI to gain the velocity but I would also prefer to keep 5 in the mag.

Any experience with any 257 Roberts stuff welcome.

Thanks.

ETA.

Does a SAAMI spec chamber work with the longer 134’s?

 

[Chris in TN]

I'd comment on this even without this question, because this is right up my alley of cool things to watch, but...

Why does magazine capacity matter? I've shot 3 deer with 3 and 4 shots when we had places to hunt with lots of deer, but that was rare, and most times I'm pretty content with 1-2 rounds in the magazine, especially hunting near home. I've never fired more than 4x in a day of big game hunting.

So a 4 round magazine wouldn't be an issue to me, in any way.
YMMV.

(My 98 Mauser sporter used to be a slow twist .257, but that was ages ago)

 

[Q_Sertorius]

I have not personally tried it yet, but I foresee no difficulties with 134-grain ELDM’s in my 1:8” twist .25-06 (based on reports from others who have already done it). I’d expect no issues with a 1:8 twist with the light bullets at .257 Roberts velocities.

I never measured the twist rate on my .257 Roberts, but it shoots the 117-grain loads very well.

I do like the idea of a 1:7.5” or 1:8” twist Roberts pushing out 134-138 grain bullets. That almost turns it into a 7x57 with a higher BC.

On the other hand, if I went for 1:7.5” or 1:8” twist, I would also plan to not waste powder and barrel life shooting lighter bullets. I did that for years when I was a poor teenager and couldn’t afford another rifle, firing many, many 70-grain .257 bullets. Never again. If I want to shoot 69-88 grain bullets, I have a .223 and a 1:8” twist 22-250.

Edit - I also don’t like AI cartridges or think they are worth the trouble.

 

[Chris in TN]

Edit - I also don’t like AI cartridges or think they are worth the trouble.

So - just a FWIW.....

I generally think of new brass as needing to be 'fireformed' for any rifle. So there's no real difference to me between an AI case and a standard case. Grab new brass, load up something near maximum seated long, shoot, now you have 'new' 1xfired brass. Same process as any standard chambering.

I built my .280ai before AI brass for it became common. I fireformed Nosler .280R brass then bought a bunch of Geco 165(?) grain .280R ammo and burned it up at the range for brass. That stuff had an almost round-nosed bullet but still shot great out to 600 yards.

But I'll freely admit that I was happy when Peterson started selling .280ai brass.

 

[Wrench]

Mag capacity is the same. 1:8 is enough.....and unless you are sitting on a pile of brass, I'd go right to a 25-06 or 08. Bob brass is hard to source and harder to source quality brass.

 

[BLJ]

The difference between 4 and 5 doesn’t sound as bad when someone else says it.
I’d just prefer to not give up what I have. If possible.

120 grain Partitions will be as light as I go.
I have 243/22ARC/223 for smaller.

I know brass is an issue. I have about 250 pieces of older Remington, with 100 of that being new from the 90’s.
I think that will suffice for my needs from this rifle.
And I’m not opposed to resizing other cartridges to get what I need. The correct head stamp isn’t an issue for me.

And I’m pretty set in cartridge. It was given to me as a 257 and unless something unexpected happens, it will stay that way.

Any info on the difference in velocity between standard chamber and AI?

Thanks.

 

[jfk69]

Agree on the 4 vs 5 not mattering to me. I’ve never shot that much hunting. 1:8 twist will stabilize the 133-134 bullets just fine. My 1:10 twist .257AI shoots everything up to 120 grains flawlessly. The AI will get you 100fps more with any weight bullet for ~5% more powder. The 257AI has a coolness factor that vanilla calibers don’t have lol. I love mine, built on a 1910 Mexican small ring M98.

 

[Chris in TN]

man, 2025 me sure would like to go back and explain to 1988 me how awesome a 20” .257R would be. I still have enough ammo to get started:

 

[West2East]

I love AI cartridges, they look sexy. There's something about a 300 Norma AI cartridge sitting on the table.... do it!

 

[BLJ]

Anyone have any numbers for a 257 AI from a 20” barrel? Preferably with something 120 grains or heavier for an idea.

 

[TaperPin]

257 Roberts brass is still available new in Nosler or Remington.

 

[BLJ]

Wonder how 90’s era Remington brass compares to today?

 

[jfk69]

Don’t know how they compare, but I’m still shooting Remington and Winchester brass from the late 90’s in mine. Some of it has 12+ firings on it. Primer pockets still good. I only FL size it when it gets tight, every 6-7 firings. Otherwise neck size with a Lee collet neck die. Love never needing to trim it.

 

[Chris in TN]

Anyone have any numbers for a 257 AI from a 20” barrel? Preferably with something 120 grains or heavier for an idea.

I could plug some numbers into GRT but I'd need to ask what pressure limit you want to go to.

Standard .257R is like 54kPSI then there's a +P version that goes 58kPSI but to be honest if I was building a modern rifle and using modern brass, I'd likely put together loads that went up into the 60k-64kPSI range.

You see something similar with a lot of older cartridges - if you take two barrels made from the same materials and use brass from the same maker in both and, say, the .243W has a SAAMI pressure limit of 60kPSI ad the 6mmCM has a limit of 62kPSI....if you just build load data to max SAAMI pressure and stop there the comparison looks different than if you load both to the same pressure.

I'm usually not prone to hotrodding anything, but when you are dealing with older cartridges using modern brass in modern rifles, I'm willing to tweak what is meant by 'hotrodding'.

 

[BLJ]

No idea on pressure.

I know my dad has used 87 Hornady SP over 47.5 grains of IMR 4350.
Whatever that makes.

 

[BLJ]

Also to note.

Douglas will be doing the rebarrel.
Since it’s an old military Mauser action they will test the Rockwell hardness to see if the action is in good shape.

 

[RockAndSage]

OP, no personal experience with .257 Robers, but very interested in a couple of AIs, and have been watching info on it over time. So, take this for what it's worth:

1) .257 Roberts got the biggest improvement in velocity over any other cartridge Ackley worked on.

2) Given you're in WV, if you aren't planning on taking shots over 400yds, there's absolutely nothing a super fast 87gr bullet won't do for you. Faster and flatter is generally better for most people out to about that distance, everything else being equal. Heavier, longer, better BC stuff matters more out past 400ish, or slightly at those distances in bucking wind. It might matter a bit if you're thinking about taking elk or moose, but even then I suspect it wouldn't make that much of a difference in terms of penetration requirements to do the job. If you have to stick with that 1:14" barrel, the lighter bullets are fine in realistic distances.

3) My understanding is that the issue of excessive RPMs with too high of a twist rate for light bullets is mostly just overblown. Spinning too fast would only matter if it pulls the jacket off the bullet, not for accuracy. When bullets do go *poof*, it seems to be clustered around thinly jacketed match .22 cal bullets with really overbore casings, with rifling designs cutting a bit too deep into the jacket.

4) Be sure to have a gunsmith with actual experience and knowledge of AI chambering procedures - barrels need to be set back a hair, IIRC, and a lot of inexperienced smiths don't realize this about AI chamberings.

Again, no first-hand experience with any of this yet, but those are some of the understandings I've picked up over time on the subject.

 

[BLJ]

OP, no personal experience with .257 Robers, but very interested in a couple of AIs, and have been watching info on it over time. So, take this for what it's worth:

1) .257 Roberts got the biggest improvement in velocity over any other cartridge Ackley worked on.

2) Given you're in WV, if you aren't planning on taking shots over 400yds, there's absolutely nothing a super fast 87gr bullet won't do for you. Faster and flatter is generally better for most people out to about that distance, everything else being equal. Heavier, longer, better BC stuff matters more out past 400ish, or slightly at those distances in bucking wind. It might matter a bit if you're thinking about taking elk or moose, but even then I suspect it wouldn't make that much of a difference in terms of penetration requirements to do the job. If you have to stick with that 1:14" barrel, the lighter bullets are fine in realistic distances.

3) My understanding is that the issue of excessive RPMs with too high of a twist rate for light bullets is mostly just overblown. Spinning too fast would only matter if it pulls the jacket off the bullet, not for accuracy. When bullets do go *poof*, it seems to be clustered around thinly jacketed match .22 cal bullets with really overbore casings, with rifling designs cutting a bit too deep into the jacket.

4) Be sure to have a gunsmith with actual experience and knowledge of AI chambering procedures - barrels need to be set back a hair, IIRC, and a lot of inexperienced smiths don't realize this about AI chamberings.

Again, no first-hand experience with any of this yet, but those are some of the understandings I've picked up over time on the subject.

1) Hope so.
2) The 87’s kill well. They’ve proven that long before I got the rifle.
The thing for me now is that I’m not going to sell the rifle and I want to set it up the way I want to hunt it. While keeping the nostalgia involved with the current cartridge.
I understand that for around here it is great, but if I ever get the opportunity (antelope, elk, wolf, mule deer) something better in the wind would help me out a lot.
3) I’m seeing the same after reading a little bit. Not really an issue.
4) Haven’t checked into this. Honestly assumed that Douglas would be capable but is a question I’ll ask when the time comes.

Thank you.

 

[RockAndSage]

1) Hope so.
2) The 87’s kill well. They’ve proven that long before I got the rifle.
The thing for me now is that I’m not going to sell the rifle and I want to set it up the way I want to hunt it. While keeping the nostalgia involved with the current cartridge.
I understand that for around here it is great, but if I ever get the opportunity (antelope, elk, wolf, mule deer) something better in the wind would help me out a lot.
3) I’m seeing the same after reading a little bit. Not really an issue.
4) Haven’t checked into this. Honestly assumed that Douglas would be capable but is a question I’ll ask when the time comes.

Thank you.

Saw your comment about Douglas after I posted this, that sounds like a really good idea. Very cool of them to be able to test the steel of the action for you too.

 

[BLJ]

I agree.

I’m assuming it’s still in good enough shape but I’ll find out for sure.
They said if it isn’t up to their standards for a barrel swap, they don’t charge for the test. Seems fair enough to me.

And it supposedly has a Douglas on it now.
That’s what dad was told when he bought it.
I haven’t been able to find anything that would indicate that, though.

But if that’s the case, it was in good enough condition the last time they did it.