Changing brass

Mick Miller

Well-Known Member
I have a really lovely load for my 260, 44gr of RS62 behind a 140gr, Hornady Match bullet in Remington brass reliably prints a 12mm group at 110m (ten shots).

However, the brass is coming to the end of its life, plus it was donated brass that had been sized from 243 up to 260 and I only had a hundred cases. I have over the last few months been slowly buying up Peterson Match brass, I now have 400 cases ready to swap over. Clearly I need to work up the load again but, I imagine, there's no need to start all the way from the bottom again, just drop 1/2gr - 1gr. and work up again till I get to a similar velocity, keeping the seating depth and everything else the same.

Case capacity is different though. Rem brass gives me 54.6gr H2O, whilst the Peterson brass only gives me 52gr H2O - am I in the right ballpark here, start 1/2-1gr. lower and work up or do I need to start lower?
 

Primate

Well-Known Member
When I change to my next lot of brass in .260 i intend to start 1 grain under my current load and chronograph them. I've done this previously and was fine. I'll then tweak either up or down accordingly looking for the same velocity as old. I think maybe 10% under is a bit ott when using the same bullet, seating depth and powder. Your already part way there in what you aim to achieve and I think you'll just be unnecessarily wasting barrel if you go down 10%. I'd agree go lower if you were changing other variables too though.
 

stevenedwards

Well-Known Member
I have found similar with peterson brass in my Creedmoor interms of a smaller capacity of 2 gr. compared with starline. I ended up with all other dimensions the same but a charge reduced by 0.3 gr. grouping the same velocity down 10 fps. I started a grain down .
 

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