AI load question

[KDX]

As a rule do the AI variations typically take about 10% more powder or does it vary from caliber to caliber? The reason I'm asking is because I will be doing some load development on a .257 Roberts AI and if I know I will be adding approx 5 grains of powder to Hodgdon's published max I would start at about 3 grains extra and slowly work up from there instead of incrementally working up from the max listed. I usually move up in .2 grain increments.

 

[Mur]

I would start at the manual's max loads for the Roberts and go up a 1/2 grain at a time,watching closely for pressure signs.There is no hard and fast rule for case capacity increases with Ackley chamberings and the case capacity of donor cases can vary from one brand of brass to another!Go slow and watch for pressure,the Nosler #6 manual has loads for the .257 Improved if you need them.

 

[Chinbullco]

257 ai

As a rule do the AI variations typically take about 10% more powder or does it vary from caliber to caliber? The reason I'm asking is because I will be doing some load development on a .257 Roberts AI and if I know I will be adding approx 5 grains of powder to Hodgdon's published max I would start at about 3 grains extra and slowly work up from there instead of incrementally working up from the max listed. I usually move up in .2 grain increments.

Using 257 Roberts load data, I would start at or near maximum powder charges with heavy bullets and slowest burn rate powders listed and increase in .5 gr. increments. Hornady load manuals have 257 AI load data.

 

[notsorichguy]

I have no xp with a 257 AI, but I do on a 243 AI.....

When I first started building a load I was told between 5 and 10% more powder. I found that I was able to add a fair bit of powder before I was able to see any pressure signs.

I started at 45 grains of 7828 and worked up from there in .5gr increments. I started seeing signs of pressure at 52 gr. I backed off to 51 as a max load. I then did an accuracy ladder just to see; 51.2gr, it also likes 48.6gr. 51.2 is the most accurate in my rifle, too hot (IMO) to shoot in the summer, but nice in the fall or winter.

YMMV

Cheers!