I make my 7-30 waters from 30-30 brass. I bought a hornady neck sizer the other day and set it up to neck size the 7-30 shells.
It wouldn't squeeze them down enough so that the expander ball had friction going back through the case mouth. I can push my bullets into the case mouth by hand. I checked thickness with my caliper and it only was .009" vrs about .013" for most other brass.

Is all 30-30 brass this thin??

If you bought the Hornady 7mm neck sizer, you got the wrong one. You will have to get a 7mm short sizing die. I had the same result with a regular 7mm neck die. I called Hornady and they told me no I had to have the 7mm short for 7-30 Waters.

yeh, I bought the regular one hoping it would work all the way from the waters to 7mm mag. It works on the 7 mag just fine and it does work on the waters too, it's just that the 7 mag brass is alot thicker so it does a proper sizing there. Maybe the 7mm short has alot tighter tolerance to shrink down the necks on the small cartridges?? Confusing--you'd think 7mm would be 7mm??

Don, 30-30 brass has a real thin neck. On top of that Remingtons weigh on the average 128-130 grains, Winchester (old) 133 grains, new 140 grains and Federal up to 143 grains. The outside dimensions are the same so in my single shot 30-30's I can gain lots of velocity by just using mainly Remington cases and the older Winchesters, without increasing pressures. I have found with stout loads the brass neck might split after 2 or 3 firings.

Haven't quite figured out what to do with the Federal brass as of yet. I buy mixed lots of once shot brass for 3-4 cents each but I am starting to collect lots of Federals and they just don't work out for what I am doing.-----------Chainsaw