Originally Posted by Lefty7mmstw
yep, that too. Both jacket and powder fouling affect groups and will distort results.
I wonder if there's enough crap(soot) in primers these days to affect the groups; cci used to toss a huge amount of soot years ago, but fed barely had soot.
Can anyone wade into that one???
This is the reason that I clean between test.
Once I tested a 416 for accuracy and I shot 50 rounds through it (I was Tired of getting the
crap kicked out of me and the fun had gone out of it). all of the loads were simular and didn't
give me much information.
So I went home and cleaned back to bare metal (No Copper fouling) and regrouped.
I felt the loads were better and that I should have seen more difference. So I loaded
the same loads and prepaired myself to start over.
A few days later I went back to the range and changed my procedure to the one I now use.
The difference was amazing. some groups went from 1 to 2 MOA to 1/2 MOA with the best
being a solid .342 5 shot.
After loading 25 of this load I made another trip to the range. This time I cleaned, shot one
fouling shot and commenced to shoot and cool (NO cleaning) the accuracy was still as good, if
not a little bit better(I was beginning to enjoy my self in spite of the recoil) the groups started
opening up after 7 shots and after the 9th shot the group had reached my limit of acceptability.
I continued to shoot the rest of the 25 loads and somewhere around the accuracy had fallen
off to over 1 MOA.
So my conclushion was that the first group of test was mask by the fouling and useless.
Now I can normally find an accurate load within 10 to 15 rounds (I shoot 3 to start with and
monitor SDs and ESs and when a possible winner is found I load and tweak it.
This process has saved me lots of pain and suffering,bullets, brass, money and time.
Others will disagree But it works for me and most of my personal rifles tested this way
will shoot under 1/4 MOA with the best being .034 .
J E CUSTOM