257 Roberts AI starting load with 134 ELDM's

[Philly]

Just built a Roberts Ackley 7 twist and would like some starting loads to try with these heavies if anyone has any info. I do have a new lb of Hunter that I wouldn't mind trying as well. thanks!

 

[SD guy]

Sounds like a neat project, mind if I ask what action this is built on & what brass you intend to utilize? have you looked at extrapolating 25 creed data?

 

[Philly]

Sounds like a neat project, mind if I ask what action this is built on & what brass you intend to utilize? have you looked at extrapolating 25 creed data?

I had a bad chamber in a 25-06 AI I built a while ago so I cut a couple inches off and rechambered it to the Roberts. It's built on a 700 LA. I thought about using the CM data to start but if someone has the info, I'd rather save some powder and lead working up my own load. lol. I scored 100 new pieces of Winchester 257 Roberts brass.

 

[SeabeeKen]

I have a lot of loads ive tested in 257ai but unfortunately, none with bullets that heavy

 

[LCazador]

Use any of the plus P loads in the latest Sierra manual.

 

[Philly]

I just tried 43g hunter. No pressure signs. .763” first 5 shot group wasn’t bad shooting from an eBay bipod at a box at 100. My chrono had a dead battery so wasn’t able to check velocities. I will load more with a hotter load later this week.

 

[Philly]

Use any of the plus P loads in the latest Sierra manual.

Does the sierra manual list the heavy bullets?

 

[LCazador]

I just tried 43g hunter. No pressure signs. .763” first 5 shot group wasn’t bad shooting from an eBay bipod at a box at 100. My chrono had a dead battery so wasn’t able to check velocities. I will load more with a hotter load later this week.

A 43 grain? I'm sure that's a typo but personally a think you're wasting time trying to shoot anything heavier than 115 grains. Been there done that. You need a bigger case to do that.

 

[358WCF]

A 43 grain? I'm sure that's a typo but personally a think you're wasting time trying to shoot anything heavier than 115 grains. Been there done that. You need a bigger case to do that.

Thinking that was 43 gr of Ramshot Hunter powder. The 257 Ackley will come damned near to 25-06 velociities. That might be fast enough considering they are being loaded in the 25 needsmore.

Philly,
If you can find data for the 134s in a standard Roberts, an upper level load should be a good place to start. Remember, the Roberts still has a low SAAMI pressure for some damned reason. All my Ackleys like to be run warm. The heaviest I've shot from my Ackley Roberts are 115s with RL23, so guessing something slower than that for the 134s may be mo better.