Posted: 6/2/2016 12:40:16 PM EDT
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I'm not new to shooting but just getting into long range / precision shooting. I don't have a chronograph yet. It's on the list, but I was anxious to try out a new rifle so I set up some targets at 400 and 600 yards. I made a ballistic chart using factory data for FGMM 308. If I play with the velocity I'm using as a base calc until the 600yd POI matches up with my real world data should that get me pretty close until I can actually get a chrono? If I did this at 400yds would it accomplish the same just not quite as accurate?
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If you did it at a couple ranges like 200, 400 and 600 and had every other variable correct you might be close out to 600-750yds.
At 400 alone you won't be very accurate. You can spend $100 in ammo fucking around or just buy a $100 chronograph. A chronograph isn't just for drops it is also used to check the quality of your ammo. You might find your ammo shoot .75 MOA and think it is great, when actually it has a SD of 20fps so it will suck at long range. Hits will by up and down and you won't know why. |
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if you know your exact distance to the target, measuring velocity at 300-400 yards is doable and accurate. if you don't have a chrono, that's what you should do. basically, on a low wind, overcast day, get a tall sheet of paper, aim at a spot on the top of it, and measure the distance the bullet falls, then calculate
if you have a nice tight, mostly horizontal group, then you can be reasonably confident in your velocity. if your group looks like a yard sale then you need to fire a large number of rounds to get a statistically relevant number. |