Home Forums Reloading Big Game Rifles 257 Roberts, IMR4350 and 115NBT

I'm working on loads for a 257Roberts.

115 NBT, on the Hodgdon site it lists 45.5gr as max for a MV of 2866.

It gives the pressure for this load as 46,600cup which would roughly relate to about 52,700psi, which I don't consider a high pressure.

My Nosler #6 lists 40.0gr of IMR4350 as max for a MV of 2806.

That seems like a lot of difference, what gives? What Am I missing?

Thanks for the help.

Dude, first of all according to some IMR4350 is very temperature sensitive, my rifle shoots great with it, but I don't use it in my field loads. Next if you shooting deer then a 100 grain bullet (I use the TSX) is all you need. So load a 100 grain bullet over 45 grains of H4350 and see how it shoots. Mine shoots good with 47 grains with no signs of pressure. I have a better load with a max charge of H4831SC that shoots into better than 1/2 inch I think its 49 grains but I forget....the Roberts is way underloaded in the press...
so the H4831 is the least temperature sensitive and the IMR4350 is the most temp sensitive.. Good luck...

anyway if something walks away from a 100 grain TSX at 3000FPS you don't want it anyway..

cheers...

jimmyp- thanks for the heads-up on the IMR4350, I've been using it for about 40 years in my 270, and I had no idea it was a problem.

I was concerned about the load data and the difference in the two. I usually cross reference, but don't remember previously encountering such a swing, especially since the Hodgdon data/pressure appears to be on the low side of modern cartridges.

I am sure the TSX is a good one, but I personally don't/haven't used them. And you're right, I don't want to meet anything that walks away from a 100 gr tsx.

Where bouts in GA are you? I'm up near the Fl/GA line.

Might want to re-check your data. 45.5 gr IMR 4350 under a 115 gr. bullet would be a very hot load indeed. Think you may have accidently stumbled into 257AI data. Nosler also shows 45.5 gr. for the AI version. One of the drawbacks of having data for standard and improved versions of the same cartridge in the same book.

I just checked the Hodgdon data and they don't even list the .257 Ackley.

And yes, they do list 45.5 grains of IMR4350 as max with the 115-grain Nosler Partition in the standard .257 Roberts. This seems a little high to me, especially at the listed pressure, but....

IMR4350 does tend to lose some velocity in cold temperatures, though the latest versions may not lose as much. In my tests it has lost 120-150 fps from 70 to 0 Fahrenheit.

JB - In response to your post, can you recall offhand roughly what the velocity loss might be between 20 or30 and 50 degrees? Also, the 45 gr. load behind a 115 looks pretty hot to me.

My .257 Rob. likes H4350 best. Did you see the new powder, hybrid 100 v, on the Hoogden sight? I'm going to give it a try.

to date I have found H4831SC to be the most consistent and accurate powder in my rifle. As a bonus it is my recollection that folks on the campfire have proved it does not lose velocity in the cold.

I have a new jug of IMR 4350...hmmmm. I haven't seen the new hybrid powder. I'll look it up on the Hodgdon site. What kind of loads are you all using with 4831 and 100s or 117s? Velocities? I have 4831SC but went straight to the 4350 loads and haven't looked back. I keep meaning to try H414/Win 760 but just haven't gotten around to it. My '06 shoots itty bitty groups with 414 behind 165s and I thought I'd try it in the 7x57 and 257.

JB, I can't remember 0 degree weather in these parts.

If I was headed somewhere really cold, I might have to reconsider.

BRoper-I have some of the Hybrid 100V loaded up and will see how it does when I return to the range. I shot some on my first trip out, it's a new rifle, but I was having problems with the brass/primer pockets.

JimmyP, I have some 4831sc, what loads with it would you recommend?

Nosler lists IMR 4350 as a most accurate powder, of course they list it as 40.0 max in the #6.... That was why I was trying it out, and it seems sorta like an old friend, I've been using for such a long time.

AJD - I'd also like to know about the Hybrid. My 257 has a taste for 4350. I am getting consistent accuracy with everything from 87 - 117gr. Loading 42.5 behind 117s and 43.5 behind everything else.

I'll let you know what I get. It seems like it ought to be pretty good powder.

Do you know what speeds you are getting with the IMR4350?

FWIW, back when I noticed the difference in the Nosler data and the Hodgdon data, I checked with some of my other manuals. I have some of the older Speer, Sierra and Lyman, I didn't however check the Hornaday manual. They don't exactly co-relate, but as I recall, none of them list anything near a 45.5 max load in somewhat similar weights.

The 45.5 gr. recipe is over the top for anything I've seen listed and I was cautioned about mixing 257AI data with 257 +P loads. I don't have a chronograph and am working in faith on the basis of my manuals. I have found very good accuracy will all of my rifles using slightly below max loads and have stayed with them. The results in the field have been excellent.

QuickLOAD agrees with the others that 45.5g is WAY over pressure for the standard 257 Roberts. With a 24" barrel and a COAL of 2.775" the estimated pressure is 67,220 psi with 3,081 fps estimated muzzle velocity.

QuickLOAD predicts that 41.5g to be max with that combo (@ 2.775" COAL & 24" barrel) for 2,822 fps. That Hodgdon data seems way out of line...

Thanks!

I was thinking to see if I could get in touch with Hodgdon and ask them to verify the load.

I'm betting they stand behind it. It looks in line with their data of other similar sized cases.

I called Mike at Hodgdon, he says their data is good to go. They shoot their data in real barrels and measure the pressure to get the results. He also stated the NBT is a softer bullet than the NP and one would get higher velocites and/or less pressure.

Bottom line, its not a problem.

AJD- I'd be interested in knowing how the new hybrid performs. I haven't found it in the stores here.

I'll post the results when I do.

50 grains in WW cases under a 100 grain TSX at 2.810 OAL
also see the next target 47 grains of H4350 under the 100 TTSX

jimmyp, what rifle are you using?

Those are nice, good shooting!