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View Full Version : target analysis and barrel twist


trinydex
04-14-2008, 1:53 PM
so i have found a few target analysis pictures

http://www.ammoman.com/graphics/diagn_left.jpg

http://www.ammoman.com/graphics/diagn_right.jpg

http://www.lasc.us/correction_chart_logo_small.gif.jpg

but i was wondering if bullet size/weight/grain in relation to barrel twist has anything to do with point of impact shifts.

my usp .40 seems to spit out

40 S/W 180 GRAIN
TACTICAL JACKETED HOLLOW POINT
LAW ENFORCEMENT AMMO

that i got from ammoman about 1-2" to the right (i'm left handed)

so my groups for 165 grain reloads and independance ammo will be centered, pattern size for independance is tighter than with reloads.

the federal hollowpoints are even tighter than the other two aforementioned full jacket 165 grain rounds but the impact is just 1-2" to the right. is it just the increased recoil changing how i "need" to stance the gun, or does the bullet weight/size have something to do with poi?

What Just Happened?
04-14-2008, 5:34 PM
I was reading that bullets fired from rifles do have drift that is associated with the spin incurred by the rifling, but that only became noticable about 500 or so yards out. At typical handgun shooting distances, it's probably you. The difference between the group sizes in the varying ammo types is probably something caused by the quality control of the ammo. I know that WWB gives me groups half the size of the Miwall reloads.

redcliff
04-14-2008, 7:47 PM
Your sights will really only be accurate for one load unless you're lucky or they share same bullet weight and velocity. Pick your poison and adjust your sights for that load.

trinydex
04-14-2008, 8:59 PM
does that have more to do with barrel twist or just velocity affecting poi