1. i have some 7x57 brass that is 2.270" overall. every manual i look at says to trim these back to 2.225" i have tried the cases in my rifles and they chamber in all of them. is there any particular reason why i should trim them? 0.050" is a whole lot of trimming. i wonder if the extra neck length might cause a pressure issue. other than that, i can't think of any reason to mess with trimming them. thoughts??

2. i made some 7x57 brass from some 8x57 brass. i am having some real issues sizing them. the situation is that, as i extract them from the die, they are pretty hard to get over the expander button on my dies (dies are Hornady). i wonder if i need to ream the necks. the brass is 0.016" in the neck. isn't that a bit thick?

i appreciate any advice or comments. thanks.

My Hornady book says 2.235 and Pet Loads says 2.244.
.016 neck wall thickness will give you a cartridge neck diameter of .316; SAAMI chambers are .3217 plus .015, so that will work. Use case lube for the necks too.
Might anneal your 8mm necks first.

SAAMI chamber length is 2.255 + .015
So if you have a US made rifle, you are good with 2.270 brass.

The empty brass may very well fit your rifles but with a bullet seated in the same case, you could easily get neck pinch on the bullet which will spike pressure and create inconsistent accuracy.
At least trim to cartridge spec length (whatever that is) even if you don't want to trim all the way down to "trim" length.
Zeke

Spend $6 to get your proper trim length for your particular rifle. The results may surprise you (ie you may rarely have to trim again)

http://www.sinclairintl.com/re...-gage-prod32925.aspx