Gentlemen, I have a puzzle.
Having just experienced a disaster at a no-sighters competition, where my "correction" from 100 to 300 meters for my Long Range Sharps put the shots over the top of the target, I finally abandoned mental arithmetic and bought a chronograph.
After establishing that the Sharps was indeed pushing out the bullets a lot faster than I had thought, I turned my attention to my Eddystone M1917. As this is the next rifle to be used first at 100 then at 300 (sighters allowed, but you just haven't got time for more than a couple!) I wanted to get the correction right before travelling.
I recently mistakenly ordered a packet of the 168 gn uncoated Lapua HPBTs, when I should have ordered the moly coated variety. As I had already opened the packet I could not send them back, so I tried using a moly spray can to coat them myself. The results looked rather rough, and so I polished the bullets lightly before shooting, thus removing most of the expensive coating I had sprayed on. As I cannot afford to throw them all away, I have been using these self-coated bullets for practice. They do not seem to group quite as well as the factory-coated bullets (no surprise).
The surprise came when I chronographed the two varieties. Please note that the cartriges were identical in every respect apart from one group being factory-coated and the other being spray coated.
The results for two 5-shot groups were:
Lapua Silver Jacket (factory coated) 828.5 - 838.1 m/sec
Lapua spray coated and lightly polished 837.2 - 843.5 m/sec
The groups are too small to make great statistical deductions, but
a) all spray coated and lightly polished bullets were faster than all the factory coated bullets.
b) Statistically weak, I know, but the variation was smaller for the spray coated group than the factory coated group.
These results are not what I had expected. My hypothesis at the moment is that the light polishing improved the surface of the spray coated bullets quite considerably.
Any comments or alternative explanations?
PatrickInformation
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