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Old July 19, 2010, 10:27 AM   #1
Brian Pfleuger
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Join Date: June 25, 2008
Location: Austin, CO
Posts: 19,578
Different Powder RESIDUE Change POI?

So, I tried 3 test rounds using Win748 in my 204 yesterday. They were: 2" high and dead center (normal), 2" out at about 10 o'clock (not unusual in itself), and 2" left at zero height (very strange). All shots fired allowed for adequate barrel cooling time and the barrel was already fouled with Benchmark.

Here's the interesting part...

This is, admittedly, a theory to fit the data, but no other idea makes any sense to me.... the order of only two impact points was unconfirmed.

The gun had Benchmark residue in it prior to that first shot of 748. The first shot, passing through Benchmark residue was 2" high and dead center (visually confirmed), the next two, each passing through more 748 and less Benchmark, shifted down and left. These were fired at a separate target from subsequent shots, so the only unknown is which was #2 and #3.

After shooting these 3, I changed targets and went back to my proven 1/2 MOA load of Benchmark.....

The first shot was at 9 o'clock 3" left (confirmed), the second shot was about 1/2 inch higher and less than one diameter right of the first shot.... the third shot was within the margin of error of where it would be expected to be under normal conditions, dead center and 1" high.


So, it seems that passing through more and more 748 residue in the barrel shifted the POI 2" down and 3" left.... and switching back to Benchmark, shifted the POI back where it belongs after 3 rounds.

Am I crazy?
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