Unless otherwise stated, all loads today used my usual load of 17.9 gr. WW 296, a Winchester small pistol magnum primer, oven treated wheelweight, sized 0.360", HVR lube, and 1.840" COL (tho the COL varied a bit
, more on that later). 27" Green Mountain barrel with a sloppy throat on a TC action.
Because the GtoB changes the length of the bullet slightly, that in turn changes how far the bullet seats into the case, which in turn changes the velocity. So we expect the velocity may be different for different GtoB's.
Temperature was a nippy 15 - 20 degrees outside, with a 5 - 20 mph breeze in my face. Temperature inside the shooting shack was 50-ish.
Procedure was to shoot three 10-shot groups for each load. The first group was for seasoning and warm up, and is not counted because it is common for a cold barrel to require several warm-up shots before it settles down. Only the 2nd and 3rd group results were counted in the final summary An exception was made for one load, more on that later.
First up, the "old reliable" GtoB 1.0 bullet that I have tested several times before. I tested it again because I believe in always including a "standard" load to compare against experimental loads.
Note that the 1st shot from the cold barrel was a good 12" to the right. If I had been shooting at a deer, it might have missed or wounded the deer. Makes you wonder.
-- 2012 fps velocity
-- 1.32% standard deviation (poor, and not up to this load's usual 0.94% - 1.07%)
-- 0.75" mean radius (not up to this load's usual 0.54" - 0.55")
-- 2.15" MOA
For some reason this "old reliable" load was not shooting as well as it has in the past.
Also, twice the action popped open when this load was fired. The first time it happened, in group #2, it resulted in a flier which I did not count (it's marked "called flyer" on the target). The 2nd time it landed within the group.
It's possible that I was careless in closing the action, or it is possible that the COL was too long and making it difficult to close the action all the way. If so, that could explain the sub-par accuracy and the sub-par velocity standard deviation. I know from experience that TC's do better with the bullet seated so that the action closes easily, even if it means that the bullet has to jump to the rifling.
I had spot checked the COL of a couple of rounds and they were running a few thou over the 1.840" target. I didn't worry about it at the time, but maybe I should have.
On to the next bullet .....