I'll put my question for you all at the top here:
I'm curious about N570. I know guys are having great luck with that. How is the Temp stability? I'm seeing N560 loose 1fps per degree drop from 85-40 degrees. Which is disappointing.
Second question is about primers. I just can't seem to get my velocity spreads acceptable even being very particular and double weighing every powder charge. I'm beginning to suspect the CCI O.E.M 250 Magnum rifle primers I got in a plain white box labeled "not for resale" are not very good. Maybe they're belt feed machine gun primers or something? who knows. I think I'm going to try a batch of my precious remaining federal gmm210's from my reserve stash (from 2018 $39.99/1000
) to see if that makes a big difference. Of course I just had to use what I could find.
For your Information:
Well after getting pretty far into development I've learned....
N560 is a little temp sensitive.
@84F 66.5g put my 195 berger @2880 from a 22" carbon Bartlein through a TBAC Ultra7.
@43F same load is getting 2830.
This was a long range sessions I'm not sure how that velocity change effected accuracy but I'm left wondering what the steel groups would look like if I had kept in that 2880 range. Bummer. BTW that steel above was in shifty 5-20mph wind so I was pretty much looking for verticle dispersion.
Seating depth on my rifle for these (berger 195 EOL hybrid hunter) was forgiving. .030-.060 jump was good.
With the Sierra 183smk it wanted to be right at .040. it really did not like less. .010-.030 opened up to over an inch groups.
My gun shot a little over 3000 with 180's, 183's, 184's, even the 195 got close (actually I don't see any velocity loss vs smaller pills which is a great surprise) but pressure seemed to be making things really testy over 3000. It would get erratic velocity and thrown shots. Some aggressive smears and loose primer pockets. So I backed up from the ragged edge of pressure to a happy place. Which in shooting multiple ladder test's with multiple bullets everything seemed to like the 2870-2900 velocity range so I went there.
Unfortunately I think N560 is less temp stable than I'd like.