The 257 Roberts has been one of my favorite cartridges for close to 40 years. My first rifle was a Remington Mod 721 with a 1-14 twist rate and it was very good with bullets in the 85-100 grain weight range. The 100 grain bullets had to be flat based because the twist rate wouldn't stabilize anything longer. When acquired the 721, bullets were hard to come by and the best powders available were IMR3031 and IMR4064. They are still good powders for those bullet weights but the velocities listed in the manuals back then were extremely optimistic to say the least. Also, without long drop tubes it was difficult to get close to a maximum load into the case. Bullet jackets back then left a lot to be desired as well. They were either very heavy and acted like FMJs or way to thin. I used to like the Western offerings but I could only get them out of the US and even then, only one or two boxes at a time. Their components were not readily available and neither were their factory cartridges. To bad because they made good stuff.
The next rifle was a Winchester Model 70 FW with push feed bolt. I used it for years with 85 grain bullets and IMR3031 powder. Then I picked up some #44 powder from Tom Higginson. I bought a lot of it because it was very close to IMR3031 in burn rate and it turned out to be interchangeable with the published loads in the books. It lasted for close to a decade then it went bad. The powder cost less than $4/pound delivered so it was a good price until the rifle suddenly went south accuracy wise. I took it on a Coyote hunt around Sheridan Lake and didn't clean it for a week. The accuracy dropped off during that hunt and I had to use a 6.5x55 back up rifle. The bore was full of rust. Not just a fine frosting but heavy, deep scales. When I cleaned it, the bore looked like someone had beat it with a ball peen hammer. I pulled all the bullets and the powder was like a solid cake in the cases. The bullets were bright green with white powder on the exposed lead base. The powder had broken down and become highly corrosive.
When I checked out the storage box I found that every can had rust inside and the smell was pretty harsh. I took that powder and soaked it in a 5 gallon bucket of water to dissolve it and threw it on my wife's flower bed. Nothing grew there the next spring. I had to bring home about 30 pounds of nitrates from work to turn the acid into a base. Thank goodness that flower bed grew great flowers after that.
Ok the point of this dialogue is first the great 257 Roberts cartridge in modern, strong actions, second to impress upon people how quickly a powder can go from being good to being dangerous. That powder was stored properly at an even 60F 365 days per year in a very dry environment.
Now back to the cartridge. Most loading tables reluctantly give us loads that grudgingly approach 50,000psi. Cartridges like the 260 Remington commonly develop 60,000psi without blinking and with similar weight bullets, so why not the 257 Roberts???
I cut some 260Rem cases in half lengthwise and did the same with some 257 Roberts cases. Both cases were Remington stamped including the 257+P cases.
Well, the 260 and 257 cases were within a few thou of each other for sidewall thickness. The 257+P were notably thicker but not as much as I would have thought. The difference is similar to that of milsurp 7.62x51 and commercial 308Win.
OK. Today I loaded up 10 cases with 38.0 grains of IMR3031, 10 cases with 40.0 grains of slightly slower IMR4064 under 100 grain flat base bullets, over CCI250 primers in Remington regular cases. I also loaded 10 regular cases with 46 grains of H414 with same bullets and primers as well as 10 +P cases with the same load.
The extruded powders filled the cases to the point they were slightly crushed. The ball powder left quite a bit of empty case even in the +P load.
The old books tell me I should expect appx 3000fps with the extruded powders. Not even close out of a 22 in bbl with a 1-10 twist rate on the Remington 700 Classic. 2780 appx average from both of them as measured over a Magnetospeed. Ok maybe the shorter barrel and twist rate made a difference??? Not that much but there were no signs of pressures with IMHO are relatively quick powders for the 25 bore. Accuracy was very good though at less than 1moa.
Next I shot the 10 rounds loaded with H414 in regular cases. Big difference, average 3026fps. This load is close to maximum in the Hornady 7th edition and well over max load (3 grains) listed in the Lyman 49th manual. Both manuals list 24 in by 1-10 twist rates at close to 45,000cup and according to their published velocities should deliver 2973 avg velocities not listed as a +P load. This brings me to the +P cases with identical components. Velocities were slightly faster and averaged 3042 over 10 rounds. The big difference was in the shape of the primers. In the standard case where there is a smidgen more room the primers were slightly flattened but nothing extreme and there weren't any bright patches on the bases. The +P cases on the other hand had very flat primers and bright spots on the bases.
I measured the webs on both types of cases and there was about .002 in of expansion on the +P case. The standard case didn't have any measureable expansion.
IMHO the 46.0 grain load is about as hot as I would like to go with this powder.
Now, just for full disclosure, I didn't start with the load I settled on with the H414. I worked up from 41.0 grains in 1 grain increments and now will stop at 46.0 with standard cases. The +P cases will be checked again with a lower charge. More likely, they will be loaded with a slower powder such as RL19 or Superformance.
Lots of fun.
I also came across an old K98 that was converted to 257AI Roberts with a 40 degree shoulder and blown out case body. IIRC it was giving 25-06 velocities with 117-120 grain bullets. It has a 1-10 twist rate barrel from an unknown maker. An old deceased (to many of those) friend Brian Oldfield built it and it is very accurate with good bullets. It's next for the experimentation with new powders, maybe IMR7828SC ??
The thing is, have fun but do it safely after doing some due diligence. Hand loading isn't rocket science as Ganderite has pointed out. If you understand how powders are made and what controls their burn rate you can get some very impressive results that are SAFE.
The next rifle was a Winchester Model 70 FW with push feed bolt. I used it for years with 85 grain bullets and IMR3031 powder. Then I picked up some #44 powder from Tom Higginson. I bought a lot of it because it was very close to IMR3031 in burn rate and it turned out to be interchangeable with the published loads in the books. It lasted for close to a decade then it went bad. The powder cost less than $4/pound delivered so it was a good price until the rifle suddenly went south accuracy wise. I took it on a Coyote hunt around Sheridan Lake and didn't clean it for a week. The accuracy dropped off during that hunt and I had to use a 6.5x55 back up rifle. The bore was full of rust. Not just a fine frosting but heavy, deep scales. When I cleaned it, the bore looked like someone had beat it with a ball peen hammer. I pulled all the bullets and the powder was like a solid cake in the cases. The bullets were bright green with white powder on the exposed lead base. The powder had broken down and become highly corrosive.
When I checked out the storage box I found that every can had rust inside and the smell was pretty harsh. I took that powder and soaked it in a 5 gallon bucket of water to dissolve it and threw it on my wife's flower bed. Nothing grew there the next spring. I had to bring home about 30 pounds of nitrates from work to turn the acid into a base. Thank goodness that flower bed grew great flowers after that.
Ok the point of this dialogue is first the great 257 Roberts cartridge in modern, strong actions, second to impress upon people how quickly a powder can go from being good to being dangerous. That powder was stored properly at an even 60F 365 days per year in a very dry environment.
Now back to the cartridge. Most loading tables reluctantly give us loads that grudgingly approach 50,000psi. Cartridges like the 260 Remington commonly develop 60,000psi without blinking and with similar weight bullets, so why not the 257 Roberts???
I cut some 260Rem cases in half lengthwise and did the same with some 257 Roberts cases. Both cases were Remington stamped including the 257+P cases.
Well, the 260 and 257 cases were within a few thou of each other for sidewall thickness. The 257+P were notably thicker but not as much as I would have thought. The difference is similar to that of milsurp 7.62x51 and commercial 308Win.
OK. Today I loaded up 10 cases with 38.0 grains of IMR3031, 10 cases with 40.0 grains of slightly slower IMR4064 under 100 grain flat base bullets, over CCI250 primers in Remington regular cases. I also loaded 10 regular cases with 46 grains of H414 with same bullets and primers as well as 10 +P cases with the same load.
The extruded powders filled the cases to the point they were slightly crushed. The ball powder left quite a bit of empty case even in the +P load.
The old books tell me I should expect appx 3000fps with the extruded powders. Not even close out of a 22 in bbl with a 1-10 twist rate on the Remington 700 Classic. 2780 appx average from both of them as measured over a Magnetospeed. Ok maybe the shorter barrel and twist rate made a difference??? Not that much but there were no signs of pressures with IMHO are relatively quick powders for the 25 bore. Accuracy was very good though at less than 1moa.
Next I shot the 10 rounds loaded with H414 in regular cases. Big difference, average 3026fps. This load is close to maximum in the Hornady 7th edition and well over max load (3 grains) listed in the Lyman 49th manual. Both manuals list 24 in by 1-10 twist rates at close to 45,000cup and according to their published velocities should deliver 2973 avg velocities not listed as a +P load. This brings me to the +P cases with identical components. Velocities were slightly faster and averaged 3042 over 10 rounds. The big difference was in the shape of the primers. In the standard case where there is a smidgen more room the primers were slightly flattened but nothing extreme and there weren't any bright patches on the bases. The +P cases on the other hand had very flat primers and bright spots on the bases.
I measured the webs on both types of cases and there was about .002 in of expansion on the +P case. The standard case didn't have any measureable expansion.
IMHO the 46.0 grain load is about as hot as I would like to go with this powder.
Now, just for full disclosure, I didn't start with the load I settled on with the H414. I worked up from 41.0 grains in 1 grain increments and now will stop at 46.0 with standard cases. The +P cases will be checked again with a lower charge. More likely, they will be loaded with a slower powder such as RL19 or Superformance.
Lots of fun.
I also came across an old K98 that was converted to 257AI Roberts with a 40 degree shoulder and blown out case body. IIRC it was giving 25-06 velocities with 117-120 grain bullets. It has a 1-10 twist rate barrel from an unknown maker. An old deceased (to many of those) friend Brian Oldfield built it and it is very accurate with good bullets. It's next for the experimentation with new powders, maybe IMR7828SC ??
The thing is, have fun but do it safely after doing some due diligence. Hand loading isn't rocket science as Ganderite has pointed out. If you understand how powders are made and what controls their burn rate you can get some very impressive results that are SAFE.
