having a discussion with a co worker about ballistics…
..and he asked if you know how a specific round will perform at a specific distance and the only way you know this is by a table set by the manufacturer for that round, and the manufacturer based this table on a 600 yard zero, how can you use these numbers to predict the bullet drop for a different zero???? I figured to tell him Chairgun…but I’d like to check with you guys first…
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Dangus; Objects are drawn by gravity to the center of the body creating the gravitational force. The the greater the mass of the body creating the force of gravity, the greater the force. Ergo, the greater the mass directly under the (toward the center) affected the greater the force of gravity.
Let’s say you traveled to the center of the earth. Whould you experience gravity? The answer is no. As you travel back to the surface gravity increases as you leave the center of the mass.
Maw has it partially correct. If the airplane is 11K AGL (above ground level) the effect of gravity would be less than below the aircraft. Now if the aircraft were at the same altitude as measured by DA (density altitude) but the terrain were mountainous, the effect of gravity would be greater. AKULA
An airplane at 11,000 ft. has less pull from gravity, then a bus on the road below.
AKULA
Can you give an example of a situation where the above would be relevant? I have thought it over and I don’t understand what you mean.
Thanks,
–Dan
Thanks Akula very interesting facts!
80; I agree with you completely. The computer models will get you on paper at long range, but only that. The gun must be shouldered and rounds put through to be able to trust what’s been predicted.
There other factors that need to be addressed:
ALTITUDE. I hunt elk at nine to eleven thousand feet. The ballistics are different to say the least when compared to sea level.
HUMIDITY How many think that the higher the humidity the denser the air? If you do, you’re dead wrong. It’s the other way round.
TEMPERATURE Do lower temps raise the density of the mass your bullet travels through? Yes.
GRAVITY Who believes the higher the elevation the less the gravity? Wrong. While on the planet, the greater the mass beneath you, the greater the gravity, hence the greater gravity affecting you bullet.
Now the next question you must deal with is to what effect each of the above affects the flight of your rounds.
I’ll stop there and see what you gents come up with as to the order and magnitude of effect on ballistics on each of the above. Show your work.
Baccalaureates in chemistry, phyics and astrophyics may be awarded for outstanding disertations. Good luck as shooting straight just isn’t enough. AKULA
Pab, yes, all that info is available for the specific rounds…so I suppose chairgun will work…but as holdhover said, the best way is the “actual way”, not virtual…
Unfortunately, my buddy will be limited in his testing as the range here only has 200 yards. Untill he gets to some larger area…he can set his zero at 200, but he won’t truly know his come ups. I told him that I have heard guys talk about chairgun being close, but not exact….Anyway, thanks for the input.
Either keep your zero at 600 and use the manufactures dope card .
or calibrate your scope and rifle to “”your zero””
say you want a 200 yard zero. fire and ajust till your dead nut @ 200.
loosen and ajust the top of the scope turrent and set it zero now tighten it back up .(resettable zero)
Now you have a 200 yard zero.now fire @ 250 yards and mark your MOA (come ups)in a notebook and fire @ 300 yrd mark. you mark your MOA (comeups)and so on and so on
that will give you a good homemade dope card that you use with that ammo on that gun . tape it on the gun or scope cover .
drop rates :
re set back to zero for 200 yards
Now repeat the same thing every 50-100 yards only dont touch the scope or the zero .leave it on zero aim right at the bull . now go and measure your drop at each range and record it.
Now you have your drop rates at those ranges . So if there isnt time to dial a shot in you can check your holdover on the scope lid
oh 450 yards = 6 inch drop Ok holdover 6 inches squeeeze , pop! target down! 😛
you have to calibrate your scope and your gun .
The trick about dialing the shots is the ability of the scope to track exactly every time you dial it.
If you use a cheaper scope that doesnt track well , you’ll pull your hair out of your fucking head , because it will always be different .
Hope that puts ya on the right track
Chairgun needs fps, grain and bc values to crunch the numbers.
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And if you were over mountains of magnetite and other highly magnetic rock formations the isostatic gravity would increase (by aprox 10-20 Mgal) A deep water lake would decrease the isostatic gravity by -10 to -20 Mgal…
http://pubs.usgs.gov/of/2009/1157/of2009-1157.pdf
The area of the highest isostatic increase is where old volcano shafts have been exposed by erosion… 😯
I did a college project based on some of this information. Local gravitational topographic maps are available from USGS…