Bumping up this old thread.
Finally did some initial testing with N555 on 6GT.
This was a pretty hasty load work up. I ended up loading 120 rounds .4grn above what I'd tested & headed for a match last weekend.
6GT
26" PVA Rock Creek cut rifle 7.5T
Prime Hornady once fired brass. Annealed, full length sized with .002 shoulder bump, trimmed 1.716, 21st Century .242 mandrel
I love to hear others thoughts on mandrel size?
My seating pressure was very consistent based on feel, but it felt low. I might try a .2415 mandrel if I can find one.
Charges were done on a chargemaster & I counted 4-5 kernels of the 555 to change scale by .1
109 Berger touches lands in my barrel @ 2.613
CCI #41
N 555
All seated at 2.583 COAL
37gr = 2809 avg SD 14
37.3gr = 2847 avg SD 11
37.6gr = 2865 avg SD 12.5
37.9gr = 2894 avg SD 9.8
38.2gr = 2907 avg SD 7.4 no pressure & not compressed
The above all shot under .5 moa with 37.9 and 38.2 a little better.
So based on that I loaded the rest @
38.6gr = 2920 avg SD 7.4
All velocities were with a Magnetospeed
Tweaked the 109 G7 to .298 to get AB lined up at 1000y
Never put a group on paper of the above load before the match but it shot well.
I've got about 15 rounds left from the match so I'll seat them deeper in .010 inc & put those groups on paper.
The Vit N555 seemed to just get better as the charge went up. It was a Hot as hell at the match today & zero pressure signs.
If I don't wind up having to seat deeper I'll try stuffing in 38.9gr next & that's going to be compressed.
The 38.6 info above was 5 x over the magneto & first shot was with a cold clean bore.
First shot was a little slow, then it got happy.
38.6gr Brass