Load Developement - Again

Thedad;

Never been a factory round down the barrel of the gun. 

900F

From the sound of it you are using a progressing press.
That very well may be the source of the problem. When you
use a progressive with rifle loads you should use a
automatic case trimmer. If you don't you will get random
high pressure loads. The majority of the stretch of a
case happens during resizing. Most people I know who
load rifle loads with a progressing check the length
before they put the case in the loader. That is wrong you
need to check case length AFTER the resize. Some people
get by with this because they have a gun with a long
throat and a little extra case length does not bother
them, however, if you have a gun with a short throat and
you get a long case then you are asking for problems.

MtElkHunter;

I appreciate that you're trying to help figure this out.  But, you're not paying close attention to what I've been writing:  "I always weigh all rifle powder charges with the sole exception of high-volume .223, which is done on a different, progressive, press.".  That's the only reference I've made to a progressive press.  I do all my rifle reloading on an RCBS Rockchucker.  With the sole EXCEPTION of high-volume .223.

Now then, I did fling several rounds downrange recently and I'm checking the fired cases.  I ran a ladder of H100V from 67 grains to 70 grains.  Due to other factors, I didn't shoot the last two rounds, which went to 71 grains.  As I sized the cases, I noticed that they were getting harder to neck-size as I went up the ladder.  So, I mike' the necks at the lip & base.  Base went .370", exactly as the manuals say it should be.  The mouth went .371", or .002" over the book specs for new brass.  Not surprising at all.  So now the question is;  what's causing the increased effort to resize?  About the only thing I can think of is brass flow increasing the neck wall thickness. 

Hmmm, but that isn't adding up with previous experience with this gun.  Hell, before all the excitement began, I'd routinely gotten up to seven reloads, or eight firings,from brass.  At that point I'd decided, again long before the excitement started, that eight was enough & never went beyond that.  I realize that this is a different powder, but something isn't adding up.  I never got to the last two rounds, which were a half grain under, and at max load according to Hodgdon's manual.

900F 

MtElk;

Not to worry, it's OK & I appreciate you're trying to help figure this out.  I've just neck-sized the brass I shot over the weekend, and I'm going to take your advice & check the case length before I go any further.  Just haven't gotten to it quite yet. 

900F

and the brass/primer looked??????????????