The weather has not been conducive to shooting but nonetheless I was itching to try out my new barrel, good weather or not.
I had built a little cover for my chronograph. Eventually it will have lighting and the goal is to be able to shoot in any weather, day or night, and still get consistent chrono results. For now I tried using a portable flourescent trouble light, but it was no go, it failed to see any of the shots. Oh, well.
I still don't have a proper rifle rest or even a sand bag. Today I started out using a Stoney Point rest, which I had acquired mainly for soaking up recoil on the 30-06. It does a good job with the recoil but otherwise is awkward and not particularly steady. So midway through today's shooting I switched to this "V" bag and an old pillow. That was an improvement over the Stoney Point but still not the greatest. Just pointing out that my range facilities are still a work in progress.
Unless otherwise noted, all of today's shooting was 5-shot groups at 100 yards, with a Mueller 4.5x14 scope set to 14x, and Rooster HVR lube. The outside weather was 20 degrees and light snow. It was 40-ish degrees inside the shooting shack.
The 200 grain spitzer had been sized nose-first in a 0.8" taper die, then pushed through a 0.358" die that actually sized to about 0.3575". Then heat treated and lubed. It was seated out so that the front band lightly engraved the rifling, at 1.995" COL. The fit was such that the TC action locked up easily, but nonetheless bullets could not be extracted once chambered. In theory that should be the cat's meow for a cast bullet.
The powder charge was 15.5 grains Lil Gun ignited by a CCI #500.
There were ignition problems with the 200 grain load. 3 rounds did not ignite even though the primer had a normal indent. Several other rounds had funny looking primers that suggested excess headspace, and all groups showed vertical stringing. The rim's headspace on this barrel is actually fairly snug, so I can only guess that either there was something going on with the engraved bullet that affected ignition, or else Lil Gun doesn't burn well in cold weather? At any rate, ignition was definitely a problem with this load.
200 grain groups -- 4", 3.9", 2.5", average = 3.5". All strung vertically.
Next up was my 160 gr. PB revolver load, with a CCI 550 primer and enough H110/WW296 to hit 1300 fps in a snub nose revolver, 1900 fps in a Marlin, and I'm guessing 2000+ fps in the 27" Green Mountain barrel. I wasn't expecting the stubby PB bullet to shoot well at rifle velocities -- it shoots 6" - 8" in the Marlin -- but just wanted to see what it would do.
160 grain groups -- 1.8", 2.4", 3.2", average = 2.5". All groups had 3 shots in a respectable cluster, suggesting that it wanted to shoot. There were no ignition problems.
Next up was my 180 gr. Marlin load, with a CCI 550 primer and enough surplus 297 to hit 1800 fps in the Marlin. I'm guessing it would easily clock 1900 fps in the Green Mountain 27" barrel.
180 grain groups -- 4.9" 3.3", 1.7", average = 3.3". There were no ignition problems.
Conclusions and Lessons Learned:
-- the fact that it shot surprisingly well with the stubby PB bullets -- at 2000+ fps, no less -- suggests that this barrel wants to shoot.
-- the fancy glove fit tapered bullet that engraved the rifling was a dog and a pain in the ass.
-- my primitive bench setup is definitely a limiting factor. Oh, I've shot plenty of good groups from improvised rests in my day, but it takes practice, and I'm out of practice. There is no doubt that a more comfortable, stable rest would help me.Punch List for Future Shooting Sessions With This Barrel:
-- get the chrono working
-- mount a strain gage
-- get a real rifle rest and sandbags
-- get a stable stool for the benchrest. I've been using a wheeled office chair, which is nice at the reloading bench, but far too loosey-goosey for shooting.
-- make a broad forearm for the bull barrel.
-- try other plain base bullets, since this barrel seems to shoot PB just as well as GC.
-- try different seating depths with the 200 gr. spitzer. Maybe it would ignite better if it did not engrave the rifling?
-- try a simple 2-diameter spitzer, rather than the 0.8 taper.
-- make a throat impression and perhaps consider sizing to 0.359", or the biggest diameter that can chamber.