V1 - Speed of sound
is ~ 1100 ft/sec
V2 -Avg speed of
bullet over distance is ~ 2400 ft/sec
T1 – Time from
hearing bullet to hearing gun report ~ 2.5 sec
T2 – Time it takes
the bullet to travel from the gun to your position ~ ?
Total Time = T1+T2
Calculate T2 =
T1*(V1/V2)
T2= 2.5sec*(1100
ft/sec / 2400ft/sec) = 1.14 sec
Total Time =
2.5sec + 1.14 sec =3.64 sec
Distance to shooter
= 3.64 sec * 1100 ft/sec = 4004 ft
Convert to yds –
4004 ft / 3 ft/yd = 1334 yds
So to simplify the
equation
Distance to shooter
= (T1+(T1*0.458))*366
(2.5+(2.5*0.458))*366
= 1334 ydsSo you look for your shooter about 1300 yds down range.
Memorization chart
using this equation.
Remember these are approximations based on sniper rifle velocities but good enough for the field. In fact one could say about 260 yds per 1/2 second or 520 yds per second.
"when you heard the bullet go by you started counting"
ReplyDeleteIt seems like relocating and taking cover or moving to a position of greater concealment would be better advice than standing around doing math. :) Besides at 1300 yrds he didn't shoot over your head, he misread wind. The next shot will adjust for the mistake, if his spotter is good, he has already pulled the trigger.
You can take cover and count at the same time. Then multiply times 520 or 260. Besides you may be in a group.
ReplyDeleteI would think you would live a few lifetimes in the fractions of a second that pass after a bullet snaps past you. I would think most would count to 45, 72 or possibly something further north rendering any range estimates useless. How about a little box with a mic and display that shows a range estimate between the last two loud noises. Heck, put this data in the ADSB packet and two, or more, boxes will have the ADSB server broadcasting the shooters location in real time.
ReplyDeleteI've seen prototype ADSB boxes the size of a pack of cigarettes so we could have troops equipped with this technology.
I think I run in a zig-zag pattern until I'm under cover. And then do the math. If he's 1300 yards out and has the dope on me, I don't want to have to have to try to see him, guess an accurate yardage, estimate the wind, figure trajectory and windage, aim and fire when he has most of that work done already.
ReplyDeleteBut it would be handy to know about where he was when you come back with a couple dozen buddies, or to call in artillery.