Home Forums Hunting & Shooting Ask The Gunwriters 257 Roberts +P vs Standard

A friend gave me around 60 new, unfired RP 257 Roberts cases. They are probably at least 25 years old. Since +P 257 Rob cases are kind of expensive these days, I was planning on using these standard velocity cases in my Kimber Montana. Are the standard cases made from thinner brass, so I should I work up standard velocity loads for them? Or... is it just that the head stamp is different to prevent someone from inadvertently shooting +P loads in a vintage rifle?

AFAIK , the +P indicates the load, the only difference. Same brass.

The .257 Roberts was never factory loaded to pressures as high as, say, the .270 Winchester--which has a standard SAAMI Average Pressure (MAP ) of 65,000 PSI--as high as SAAMI allows for any cartridge. Even the +P ammo is only loaded to a 58,000 PSI MAP--which is less than the .30-06's 60,000, and the .30-06 had been chambered in at least as many actions (and old rifles) unsuitable for higher pressures as the .257.

In other words, it's always been something of a mystery why the .257 was "underloaded," and still is. I don't know of any "vintage" .257 rifle that wouldn't easily withstand higher than +P pressures.

While some +P .257 has been thicker than standard .257 brass, this also has no practical bearing on how much pressure the brass can stand.
Your Kimber Montana can safely use handloads developing 65,000 PSI, just like any modern .270, with either kind of brass.

The OP can also look to 6mm Remington data for guidance. With like bullet weights and styles, like propellants and barrel lengths, the 257 is capable of more velocity at the same pressure.

For example, Hodgdon shows the 6mm producing over 3100 fps with 100 grain Speer boat tails and both IMR and H 4350. The listed 257 Roberts data (same style bullet, barrel length and powders) can then be used as a starting point in conjunction with a chronograph and the heat can be turned up.

I appreciate this thread. My previous 257’s have been on Mauser 98 actions.
I now have a 700 Classic 257 that looks like and may be new condition. I’m thinking that Mathman’s answer is the guide I’ll likely use. I was also wondering about brass thickness, thanks MD.
In a perfect world, some one would have tested 65,000 PSI loads in multiple cartridges. If for nothing more than seeing what the top was. I don’t NEED to go that high in a 257, having 25-06’s on hand. But it would be nice to know.
I have a new to me, a very nice Mauser 98 8x57 sporter. I’m not too interested in 30-40 level loads. I think that it might be possible to approach 30-06 velocities in same weight bullets???

I have always loaded standard brass to over standard pressures.

If some of the +P brass is thicker/heavier than standard brass, wouldn't it be prudent not to use the same combination of primer, powder, and bullet in a mix +P and standard brass?

Yeah.

In a strong action with good brass, I don’t see much difference between a Roberts and a .270 regarding PSI.

IMO, any difference is arbitrary.

DF

Yes, but it's prudent to not mix cases of any cartridge without weighing them first--even if they're the same brand and supposed type.

The only +P .257 brass that I ever came across that was significantly heavier than standard .257 of the same brand was some early Winchester cases, which of course did require dropping powder charges somewhat from those worked up with standard brass. But that was in the 1980s--and I've never encountered any .257 brass that was nearly as heavy since then.

Have some +P .257 Hornady brass from some factory +P ammo purchased maybe three years ago for an article in Rifle on a first-year production pre'64 Winchester Model 70. The Hornady brass was right in the "normal" range for .257 Roberts cases.

Great information, Thanks! Mathman, I will reference 6mm Remington data as you suggest. If I can get a 101 gr Barnes bullet to 3100 fps or close out of a 22” barrel, I’ll be very happy. Next I’ll be bugging you guys about the 250 Savage.

You can beat that speed with H-100V. This is out of a 24" Brux on a LA 700, thus the longer COAL. I've posted this one before.

No signs of pressure, cases extract freely. The 100 TTSX at that speed is a deer and hog killer. Gunner calls it a "little buzz saw" and he ain't wrong.

Now, if you want to get real fancy, try the 90 gr Absolute Hammer at 3,450 fps. Google Absolute Hammer load data. That bullet is designed with very low friction and is in an altogether different league. Terminal performance is really great; those bullets are mono's but more expansive than Barnes. I've not killed anything with a 257R Hammer bullet, just started loading it. I can tell you about the 178 Shock Hammer out of my Pre-64 FWT .358 Win. That one messed up a WT chest pretty bad.

DF

Undermountain,

Yes, H100V gets about as much velocity as possible with 100-grain bullets in the .257 Roberts.

BUT I have also tested H100V extensively (along with other powders) at different temperatures in the .257--and it's particularly sensitive to temperature changes. This may or may not matter in your hunting, depending on both temperature and range, but have seen many loads that vary widely change point-of-impact at 100 yards up to 3"--which means 6" at 200--at temperatures from near zero to "normal."

In general I use less temp-sensitive powders, partly because I live in Montana--where recorded temperatures vary wider than any other state. But have also found that another 50-100 fps in muzzle velocity (or even far more) makes no difference in "killing power" when you hit deer in the right place with a decent bullet. Which is why I tend to use more temp-resistant powders in the .257, whether shooting 100-grain bullets at 3100+ fps or 115-120s at 2900 or so.

If you want more detailed information, there's plenty on the .257 in my books, available from www.riflesandrecipes.com. I would especially recommend The Big Book of Gun Gack II, which has an entire chapter on temperature's effects on handloads, including range-tests for a bunch cartridges from the .17 Hornady Hornet to .375 H&H--including the .257 Roberts.

Among other things, I have found that heating or cooling only the ammo does not consistently reflect what might happen in the field, when the rifle's temperature also affects results. Which is why I tend to use temp-resistant powders like H4350 in the .257, which can easily get 3100+ fps with 100-grain bullets in typical 22-24 inch barrels, and 2900+ with 115-120s.

Where you are, I wouldn’t use it, either.

Where we hunt, it’s ok.

DF

The cartridges/rifles I reload for all seem to do very well with H4350 or H4895, but it seems everybody else in my area likes them too because they’re almost always unavailable. During deer season temperatures here range from around 60f to maybe 15 or 20, but I do most of my load testing on the warm end, so I’ve tried to use the one of the Extremes whenever I can, even though I’m not sure that this is enough of a temperature swing to really matter.

MD, I've been meaning to get your books. I only recently discovered Rifles and Recipes and Rifle Loony News. Your work for Rifle Mag really elevated that publication, IMO.

DF, I have a lot of confidence in Barnes bullets from using them successfully over the years so have hesitated to spend even more $ on Hammers, but they do look interesting. Recently I picked up the LRX series in the calibers I plan to use going forward: .257, .264 and .277. 257 is a new one for me, which is why I started this thread.

Hard to beat 47.0 gr Ramshot Hunter in a Rem case with 100 gr TTSX for accuracy. I average a fuzz over 3,000 fps in a 22” Ruger M77. That’s a JB load from Gun Gack. I think other loads might push the 100 gr Barnes or BT a little faster. Mine shoots cloverleaf groups with that load. That’ll take anything that a .257 Roberts is appropriate for.

I don't think that there were ever any weak factory built rifles chambered in 257 Roberts, vintage or otherwise.

I have a few rifles chambered in 257 Roberts and 257 AI, the weakest of which is either the rebsrreled Swedish 1896 SR military Mauser or the rechambered Savage 99 CD. FWIW, I use Winchester brass and have pretty much settled on the 75 grain VMax for shooting predators and the 110 grain AB for game over an appropriate weighed load of H4895.

My experience in temperature-testing is that just about any modern rifle powder will be pretty consistent in velocity between the 20s and 80s Fahrenheit. Below 20 and above about 85 is where temp-resistant powders can make a real difference--but in hotter weather they still tend to gain some velocity (and hence pressure), though less than standard powders.

Thanks for the nice words about my Rifle articles! I suspect you will like the books, partly because some of the chapters are essentially updates and/or expansions of articles that previously appeared in Rifle and some other magazines.

Might also mention that my wife has used the .257 Roberts with 100-grain Barnes TSX's on game as large as cow elk, quite successfully. She has mostly used the load listed for Hunter powder, which is listed in the .257 chapter of Gun Gack IV, Rifle Loads That Work--which was just published last fall. From the 24" barrel of her New Ultra Light Arms rifle the load gets around 3100 fps.

Have you tried the 80 grain TTSX?

The work nicely in my 700 CDL-SF's 24" barrel and still feed smoothly from the short action magazine, but are kind of expensive, compared to the 110 grain ABs, just for shooting whitetails.

Some of you fellas are loonier than me, and that's a little scary!

Question: I've whacked a few critters with old school Bobby, boom flop every time. You fellas jackin' up the velocity AND pressure are delving into a world that increases barrel erosion a fair bit. I'm OK leaving well enough alone and wonder if there's a vaccination for the condition y'all suffer?

Gotta agree with you, Dan. I load a 100 grain SGK and have killed several deer with it. I’d venture to say that 2900 fps is a little too fast for that bullet. Knocks them down for sure. I could maybe see the need if I were to take the rifle after elk like Mule Deer’s wife, but for deer I don’t see the need.