I'm a new poster and have been reloading for almost 40 years, but I'm still trying to learn some things. I bought a 257 Roberts last year and am working up some 100 grain Partition loads for it. This is going to be my doe culling rifle for our MLD program in South Texas. What my question is as follows:

Since the 257 Roberts is a derivative of the 7 X 57 - Why are the loads reduced so much from the 7 x 57 to the "Bob"?

As an example - this is from the older Nosler #4 Reloading guide.

For a common bullet - 120 grain Partitions - the loads are as follows:

257 Roberts
Max load IMR 4320 - 34.5 grains

7 X 57
Max load IMR 4320 - 47 grains

The cases are virtually identical in measurement. That's just a small example - I just wonder why the 257 is loaded so light - when the cases are the same. Maybe the answer is very obvious - you have a smaller diameter hole in the case end - thus increasing pressure.

I'm sure you guys have a better answer. I keep looking at the 257 tables in 3-4 of my older manuals (Hornady, Lyman, Nosler, etc) and it seems the "Bob" is not loaded to it's potential. I've read just about as much as a I can about the "Bob" and know all the reasons why they've done the P+ loads etc - but it just seems that you could still add more powder to it.

By the way - if anyone has a load with the new Hodgdon Hybrid 100V using 100 grain Partitions,
I'd appreciate that too - so far I'm using IMR 4350 and 4064 in my loads - plus some trial ones with the Hybrid.

Thanks for the input,

Bob with a "Bob"

75AG,
welcome to the forum!
i'm sure there are guys on here that can give you better answers, but i'll get it started with what i know....
first off, with the same size case, although greater volume in respect to the bore, the smaller bore will tend to push pressures up if you put as much powder as the 7x57 bore can use, even with a considerably lighter .257 bullet.
secondly, although i can't name the action, there were actions(guns) chambered for the roberts years ago that won't handle the pressures of a full tilt load, so the manufacturers will down-load certain cartridges because they can't control what gun thier cartridges will go in. hence, the +P loads, that are supposed to be used in only good modern guns....the loading manuals more or less are bound to follow suite for the same reasons.
i'm sure someone will come along and add to this, the guns that were made that aren't really safe with the full tilt loads.
by the way, both the roberts and the 7x57 are my two favorite deer country rounds.

I have both, and I cannot really answer your question as it has never arisen for me. The 100 grain bullets are probably optimum for the 257R (although I am still trying to get mine to shoot the 120 grain NPs). However, the 7x57 is totally different. I have never shot 120 grain bullets in mine and don't plan on it. My best loads for the 7x57 are with 175 grain bullets. I have tried 160s and 150s but nothing less than that. I regard them as two totally different guns for totally different purposes. The 7x57 has shot just about everything that walks in Africa. The 257R is a nice deer gun. That's it. It's the smaller diameter hole, but not sure it has much to do with case pressure. OTH many have claimed that the reloading books (and factory ammo) are deliberately on the "light" side due to "inferior" actions with limited strength. Hence the +P designation on some factory ammo. Similar to the 45/70 etc. etc.
Peter.

I figured it was the "smaller hole" or bullet diameter, just doesn't make intuitive sense that the difference between .284 and .257 is that great - although mathematically and pressure measured - it may be huge.

I have a Ruger - so I figure it's safe - but not gonna push it beyond what it should be.

If anyone has any experience with the Hodgdon Hybrid 100V - I'd still like to hear those loads.

Thanks for the input!

.284 to .257...(.027).... is a pretty good step backwards when you math that out to volume of a tube in relation to the same case volume.
if you measure to base of neck there's a bit of a bump in volume with the roberts case that helps a bit, but not enough to compensate for the diametrical difference.

To me a 120 in both makes no since as a comparison. I tend to look more at the same sectional density. A lot will depend on what pressure your manual or data stops at. The 257 was 54,000 +P a little higher. The 7x57 was 51,000. Is your data stopping there or going to head expansion? Loadtech stops at pressure and it gives 36.7 and 41.2 or about 12% heavier load. For reference the 284 bore area is 22% larger than a 257.

If you are going to reload 100 grain partitions, the best load I have found is using 46 gr. of H4350. Great load in all my Roberts.

Have fun,

ddj

Stick w/ the 4350 and the NP. THIS combination has been proven time/time again. It will drive the 100 NP fast enough for anything you would sanely do w/a 100g bullet. It seems to be THE go to powder(for med-hvy bullets) for all the cartridges based on the 7x57.
The difference in bore diameter is the answer. Just look at the 25,27,28,30,33 & 35cals based on the 06 case. Or more specifically, compare 150g loadings in the 270win & 30-06.

quote:

Originally posted by trouthunterdj:
If you are going to reload 100 grain partitions, the best load I have found is using 46 gr. of H4350. Great load in all my Roberts.

Have fun,

ddj

On my way up to 46.0 grains of H-4350, I shot an awesome group with 45.0 grains, so I quit.. (With 100 gr. Nosler Partitions)

merlinron hit the nerve I was talking about - the "bump in volume" to the base of the neck was the reason I was asking this question. I knew there was some "propellant engineering reason" why the "Bob" wouldn't accept more powder. This was more or less a theoretical question. At first glance, when comparing case measurements - I'm thinking slightly bigger case and volume - smaller "hole" for all of that to go through - but why the "sharp" decrease in the amount of powder?

Good to get some further understanding of the issues. Thanks to all.

46 grains of H4350 and the 100 grain TSX shoots well in my Kimberbob.

As a comparison to the 257-7x57 loads, I checked the Hodgdon web site for 25-06 and 280 loads. (Yes, I know the 280 is a bit longer body.)

With 120 grain bullets, the 280 accepted around 10 grains more of the same powder.

And 243 compared to the 7mm-08 does about the same 10+- difference with 100 grain bullets with the same powder.

Bruce

The 257 Roberts has always been under loaded in the U.S., and for no good reason, either!

quote:

secondly, although i can't name the action there were actions(guns) chambered for the roberts years ago that won't handle the pressures of a full tilt load, so the,

It has never been chambered in any weak actions, so it can be upped considerably from factory levels of loading.

Do you have a Chrony? If not, one may very well show you that even tho you add powder to the bob beyond safe limits, your velocity gains would be meager relative to the amounts of powder added.

EL deguello is right....
as i thought about it,after reading his post, there were really no "weak" actions that the roberts was in. it was more a case of mag length/action length. from memory,(for what that's worth,lately)... it was introduced in a gun with a mag length that didn't allow the bullet to be seated out where it takes advantage of the case's volume. with that in mind, manufactures have to consider that those guns are still around and used, so they have to build thier ammo accordinly to allow use in those guns today, yet. the deep seating makes for allot less volume, hence low performamce numbers.
alot of these details i've learned so long ago that it takes a while thinking about it, to bring them up,epecially when i don't deal with shooting/ loading on a daily bassis like most of the guys on here.
sorry for the mis-leading info, and thank-you ED for the correction and jarring my memory!!

I seem to recall an article that talked about the 257 Roberts and its modest factory velocity. The article talked about the period when the 257 became a factory cartridge and it was the same time that IMR 3031 was introduced. While 3031 is a little fast (burning speed) for the 257 it was deemed to be a great new powder. The modest velocity was what could safely be achieved using 3031 and for some reason the velocity was standardized even though slower powders could achieve higher velocities at safe pressures.I believe that article also went on to say that had the 257 velocities been increased utilizing slower powders that there never would have been a "need" for the 243 and 6mm Rem. Regarding loads for the 257. 4350 and 100 bullets are a good combination. I also had excellent performance in a Win 70 Featherweight usig 115 to 117 gr bullets with W785 powder. Since that powder is no longer availible nor is H450 you might want to try Mag Pro with the heavier slugs.

quote:

Originally posted by El Deguello:
The 257 Roberts has always been under loaded in the U.S., and for no good reason, either!

quote:

secondly, although i can't name the action there were actions(guns) chambered for the roberts years ago that won't handle the pressures of a full tilt load, so the,

It has never been chambered in any weak actions, so it can be upped considerably from factory levels of loading.

I believe I'm going to have to disagree with you. I've seen too many 1893 and 1895 mausers that were rebarreled to the .257 Roberts. I'll agree that there were no FACTORY rifle chambered that made weak actions but it was the "poor man's customs" that were.
I had a good friend many years ago when I was in high school that made himself with the help of his machinist father made a matched pair of hunting rifles based on the 1895 Mauser that were simply beautiful. The kid and his old man did good work. A lot of days have passed since he built those rifles and I'd be willing to bet he still uses them.
Unfortunately, that's the problem, not only with the Roberts but the 7x57 Mauser as well. Due to all the old guns that were weaker than more modern guns, factory ammo and loading data have been kept as a reduced level due to liability concerns. Seems like the 30-06 is also afflicted with weak rifle syndrome.
I can safely load my 7x57 Mauser to 2800 FPS without any problems. That's above what most manuals state and they cheat anyway. Check the barrel lengths of the test guns. In some of the earlier Sierra manuals they use an old military Mauser with a 29" barrel. WTF is that? In the newest one I have in Sierra manuals, marked 5th Ed. they are still usuing a 26" barrel. Many manuals use a 24" barrel when most production rifles have 22" barrels. They ain't cheatin' fair, sez I.
I have data for Winchester's discontinued WMR powder for the .257 Roberts that says 48.7 gr. will give 2935 FPS at 48,300 PSI. They must have used a 24 or 26" barrel because that load doesn't even come close in my Winchester M70 Featherweight with 22" barrel. Again, WTF? The load is reasonably accurate but not where I'd like it to be. methinks I'll tinker it upwards a bit and see what developes. I might as well as I have about 30 pounds of the stuff.
Paul B.

maybe I missed the point in all of this? A modern Roberts should be able to withstand the same pressures as a 6mm remington. I have lit 47 grains of H4350 behind a 100 grain TSX so far with absolutely zero signs of high pressure. Unless I am missing something I plan to sell a .270 winchester and the next time Ruger makes a run of 7 x57's buy one of those for case compatability. Then the 120/284 cannot be a wit's difference than the 130/277 and I can reduce my case inventory and size up or down....as far as I know anyway.

I think I can give decent discription of why the .257 charges are lighter.
It has been hinted at here already.
As you neck a case down or a bore , the oreasure escapes slower.
that is why you tend to use slower powders in smaller bore with the same case.
the Roberts was introuduced by reminton in about 1934, I think , and the 1st factory rifle was a model 30s. Strong enough for any cartridge.
But since remington chose to call the round the .257 Roberts (even thought the shoulder angle was changed from the ned roberts wild cat)
But the wild cat version had been built on the 1893 and 95 mausers for a long time.
If remington had called the round the .257 Remington, they probably could have loaded up.
Also, My load for the Roberts is 46 grains of H-414 under 46 grains of H-414. 3140FPS and great groups !!! My 7X57 load is 50 grains of the same powder under any of several 140 grain bullets.
Comes up just shy of 2900 and quite accurate.
...tj3006
...tj3006

The Roberts is an awesome cartridge. However, I have found that to truly get the most out of it,with heavier bullets you need to get the chamber reamed to the Ackley Improved chambering. That is when the little quarter bore really shines.

The history of the 257 Roberts is a little different than what is commonly found on the internet. Remington didn't commercialize it as the 257 Roberts, but as the 25 Roberts.

The 25 Roberts was a popular wildcat cartridge. When Remington adopted it, they changed the case shape but kept the same name, 25 Roberts. It wasn't until a year or more later that the name was changed to 257 Roberts. I suppose this was due to the owners of the wildcat 25 Roberts who could not chamber a cartridge marked 25 Roberts, and then complained to Remington.





Bruce