Post by bluedot on Aug 18, 2018 21:11:57 GMT -5
I put this here because technically it IS a wildcat. my 7mm Allen Magnum (or at least I think it is). Parent case is .338 Lapua. Case body taper reduced, shoulder blown forward and a sharper angle out on it. Bullet dia is necked down from .338 to 7mm.
Anyway.....
The go to powder for the heavier bullets (to my knowledge,, but the data is 10 years old) is WC872. Ball powder, mill spec pull down powder. For the 20 Vulcan round. When the rifle was new, the 175g 7mm SMK's worked fine at 3475 fps. After 200 rounds, they started going "POOF" at about 50 yds. So, I switched to 180g Berger VLD bullets at 3350 fps.That was the sweet spot. I had worked up the load during 40-50 degree temps and everything was fine.
Today I shot it trying to get a load worked up for the newer Berger 195g EOL bullets, and the 200g WIldcat bullets I have. I had some of the 180g Berger bullets loaded from a few years ago, and when I checked throat erosion, it had moved .015".
I prepped the brass as usual, anneal and trim to length. This time I didn't FL resize them, I just neck sized them, and only sized 80% of the neck. I weight sorted the brass into 3 groups, each group was plus/minus 1 grain. I also weight sorted the bullets into groups of plus/minus 1/2 grain and also measured the bearing surface, sorting by .001" increments.
Aside from the previously loaded ammo (18 rounds and that was FL resized), all the brass today was from the same weight group.
Neck OD was the same as the FL sized brass. Powder was the same lot, as was the primers and brass, all purchased going on 10 years ago when I bought the gun.
80°F ambient temps today, I kept the cartridges and gun in the truck with the A/C on high the whole time. Shoot 3, put in truck to cool down. Pull out 1 cartridge from truck at a time, put in gun and shoot within 15-20 seconds.
Here's where it gets weird.
Chrono set 20' from muzzle so muzzle blast won't affect it.
Previously loaded ammo that shot 3350 fps in 40-50°F temps now chrono'd 3564 fps clean cold barrel, 2nd shot was 3353 fps, last shot was 3593. Heat build up? Bore dimensional change due to temp? I could barely hold my hand on the barrel in front of the scope, so in the truck it went. No pressure signs on the cases.....
After it cooled down I thought that maybe it was due to the bullet sticking to the neck after being loaded for 3 or so years so I grabbed one of the ones I just loaded, same powder charge, same bullet weight and seating depth, only difference was the case was only neck sized. I shot 1, WTH? No bullet hole in the paper at 100 yds. Looked at the chrony, Holy crap, that can't be right 3660 fps. Look at the brass, nothing unusual. Lets send another. FM, nothing on paper. Now what? Look at chrony, 3714 fps. HUH?? O.K, enuf, I'm not shooting the 3rd one. Well, now I know where velocity range the 180g Berger VLD bullets go POOF!
Lets start with the 195g EOL bullets seated .010" off the lands.
99 grains 3349 fps
100 grains 3331 fps
101 grains 3389 fps, and a hint of an ejector mark on the brass and a bit of a draggy bolt. I've seen enough. 1st and 2nd shot are almost touching at 100 yds, 101grains is about .060" away from the 99 grain hole.
Now lets see how the 200g WIldcat bullets do.
99 grain error. WTH? Oh, because I shot at a different dot, I was off a hair to the side of the chrony, but still within the guides. Move chrony 2" to the right.
100 grains 3251 fps
101 grains 3323 fps bolt lift fine, case looks good
102 grains 3314 fps, bolt lift draggy, case looks good, no ejector mark, but I'm stopping there.
100 grain and 101 grain powder charges had the bullet holes touching, same horizontal line, so basically no vertical stringing.
So, now I have to call Kirby Allen and pick his brain about WC872 powder.