load development with new/once fired brass

[ozyclint]

Just wondering if you start a new load with new brass or once fired brass that was fired in another rifle whether it is best to fireform to my rifle before drawing conclusions from results?
What I'm getting at is would I see a difference between my current brass that has several firings on it and the new to me brass that hasn't been fireformed to my chamber yet?

I just obtained some currently 'unobtainium' bullets (Woodleigh 150gr PP) for my 270win and need to minimize how many I use to get to a load I'm happy with.

 

[cnelk]

I would run the other brass through the sizing die and then check the COAL on each piece.

Trim if needed.
I don’t think once fired brass from other rifle will matter, especially after sizing.

 

[sage1]

2nd that, I would resize the fired brass

 

[ozyclint]

I have full length resized and trimmed with Lee trimmer and cordless drill just to make them consistent.

Awaiting the bullets in the post before I can make a start

 

[jjohnsonElknewbie]

Been down this road on a couple different rifles.

1- absolutely FL size and start with 1 piece from each batch of foreign brass
2- get hornady shoulder comparator and compare the sized "foreign" brass to a known-fired piece of brass from your rifle
3- if the shoulder dimension is too long, you're going to have trouble chambering rounds
4- in this case, you will need to bump the shoulders back further to get them to load without effort. I fought this in my 7-08 most recently, and that shoulder comparator and measurement may save you a TON of headaches and rework
5- you may also need a body die if bumping shoulders back doesn't solve this issue

Good luck!