Re: How i Test Ballistic Coefficients-Matrix 175gr
That sure is impressive shooting, but more importantly, its great to see someone else who is as methodical in calculating his BC's from drop as we are. You often see all sorts of BC's bandied about by various "witchdoctor ballisticians" who have obviously discovered how to beat gravity, but no mention of how they come by these exaggerated BC's.
The use of sky screen chronos in ambient light can give you some widely varying results in different conditions that make a huge difference to your BC calcs. Inaccurate rangefinders is another variable that can give you some significant errors. We measured all our ranges from 100 yards to 1 mile with surveyors EDM measuring gear which is accurate to + or - .25inch at 1000 yards.
We also don't shoot our scopes adjustment calibration, we actually clamp the scope in a jig and measure the adjustments right through its range on a precise grid at an exactly measured 100 yards from the scopes turrets. We also leave the "up" in the scope after say shooting at a mile, and then straight away reshoot it at 100 yards and measure exactly how much up we actually had in, to work out our drops. No scope can be trusted to move what they say they will, even Nightforces!
As we measure both velocity and pressure with the Oehler 43 when we're shooting for BC, we can then correct the velocities we got on the mile range under ambient light conditions to those we've shot in our very accurate lightbox setup on the 100 yard range verses pressure and come up with a corrected accurate velocity for each shot.
We then calculate the drop for each bullet, verses its muzzle velocity, and come up with that individual shot's BC's. We like to see them vary by less than 3% to know we're getting some consistency, then we'll average them to come up with our average BC using Bryan's Point Mass solver. If you're getting BC's way above trusted sources like Bryan's database, then there's an error in your system somewhere. If something sounds too good to be true, it most probably is!
Looking forward to your continued testing!