I have one box of .338 Federal brass that reloads fine. The Winchester .358 brass sized down to .338 Federal does not develop adequate neck tension after being resized in a RCBS .338 Federal full length die, even with the expander removed. The loaded rounds mike at .004" smaller neck diameter with the Winchester .358 brass. Since .338 Federal brass is non-existent here in BC, but .308 brass including Lapua is readily available, what do I need? What .308 brass has the thickest necks? Hate to buy 50 more pieces of brass and find I can seat the bullets with my fingers again like the resized .358 brass.
Thanks!

I use Lapua brass and like it.

I've used Lapua 308 brass and it worked well.

My smith told me that reformed Lapua 308 is very close dimensionally to the Federal factory brass (but much better quality) so that is what I use.

I've used nothing but new Remington 308 brass by just running them through the 338F FL die. I hzve never had ANY issues.

RH

I had the same issues with WW 308 brass Kurt. It worked fine when going from 308 to 338, but RO was pretty wild as the exp was doing all the work. Once fire formed, the exp doesnt touch and bullets just fall in the case. Fed 338 Fed brass works like a champ, but it has thicker necks. I tried some Fed 7-08 brass I had on hand and got the same results as the 308 WW cases, useless after FFing. Now, I've picked up some Fed 308 brass to try. It has a touch thicker neck than the 7-08 brass, so it may work.

Good information here. Thanks!