How much of an increase when working up?

[Durby]

I have heard a few different suggestions for how much to increase a charge when working up a load. For standard size rifle cartridges, half grain increments seem to be the norm. My buddy claims for big cases, like the 375 Ruger we both shoot, that half grains are a waste of time, and 1 grain increases are fine, due to the big case capacity.
So I want to load some 250 grain Sierra Matchkings in my 338 Win Mag, should I use half grain increments? or go a little bigger?
Thanks

 

[depoloni]

Very interested to hear what others have to say about this one actually.

My opinion, and understanding, has always been to think in terms of percentages. Just like the "norm" when you only have max-charge data to start from is to reduce by 10% (not xxx grains) for a starting load, I usually work up in 1-2% increments there as a rule of thumb. I base that percentage on the listed max... of course if I see signs of excess pressure before I reach the max then so be it.

For rifle loads that works great. 50-grain max charge, I'll go 1/2-grain increments from the starting load. 80 grain magnum, 1-2 grains is more the norm... tend to agree with your buddy that 1 grain isn't always going to make much difference when it's a smaller percentage increase.

I do the same for pistol loads even though it means very small changes - if a starting load is generally 10% below max and you use 1-2% increments to work up, you'll usually have 5 or more load-levels to work through and unlikely to get way out ahead of yourself pressure wise. Hope this helps.

 

[ranger335v]

"...50-grain max charge, I'll go 1/2-grain increments from the starting load. 80 grain magnum, 1-2 grains is more the norm..."

Ditto, good advise.

 

[Durby]

Thanks for the quick feedback, I'm going to go weigh powder right now. Those 250 grain Matchkings look great sticking out of the 338 case...