Well as a relative new comer to hand loading I must say that taking newly loaded ammo to the range for load developement is quite a bit of fun. Had loaded some 100 grain bullets over various loads on H4350 last week and came up with Ziltch. So this week I tried some Reloader 19 and some H4831 with 100 grain triple shock. Got a nice group with 53 grains of H4831 and the best Re 19 load was with 50 grains. My rifle is a mod 70 XTR Featherwieght with a 3-9 Conquest on top. Shot at 100 meters here in Alberta. Trying to deveope this load for mule season week after next.
Had my 257 Roberts with me as well and don't have a set of dies yet for this Mod70 also a feather weight so I tried some factory Hornady 117 BTSP and they grouped very nicely. FS

Just a thought, but would not the .257 Ai dies work like neck sizer for your Bob? The IMR 4831 and the 100 grain should be a winner, the IMR 7828 and the 110 Accubond is my personal favorite these days.

Don't remember how much but my .257 A.I. likes H-380 for both light and heave bullets.

I had excellent results with 51 grains of Re19 under 100 grain TSXs in my Bullberry Encore barrel.

I will have to look at my records when I get home tonight. Reloader 19 gave me the best overall consistancy (speed, group size, and consistancy). As I remember I was using 117 Nosler Acubond.
Thanks, Doug

I have 2 Roberts rifles and an AI.
But I have not used the AI much yet.
My Roberts rifles both like IMR-4350 very well, But a couple other poweders that you really should try include H-414. IMR-4064 and one I have not yet tried but will soon RL-15
...tj3006

So now we have taken the 50 gr group and loaded 3 at 49.5 and 3 at 50.0 Barnes 100gr. Then with the Accubonds I have loaded 3 at 48 gr, 3 at 49, and 3 at 50. And the last geoup of loads with R 19 are the 117 gr Hornady at 50.5,49.5 and 50.5. Hopefully if the wind isn't too brisk tomorrow I'll get a chance to give these a try.
I have seen other info from shooters that also felt that H414 worked well for them and may give that a try if things do not go well with this current batch of loads. Thanks for your input, Greg

Greg,
Both of mine like slow powder, give RL 22 a try if your present loads don't work out.

Stepchild

Another vote for slow powders....my 257AI likes H4831 with 120 gr bullets.

Like always, I have to seen to be different and more traditional...

IN some older manuals, I have seen some fantastic velocites with 100 grainers out of a 257 Roberts, with powders like IMR 4064, IMR3031, RL 15, IMR 4895, W 748, H 380.. and in my experience, they are more accurate in that size of a case with that bore diameter...

100grn NBT and RE15 is whats working in my XP. I'm getting a hair over 2800fps with a 15" barrel.

Mine likes IMR 4350 with Remington 100 Core Lokt bullets.

Steve E.........