Help me figure out velocity and trajectory

[AdamSmith007]

Hey guys, i need a little help. I just bought a vortex viper scope and i am trying to figure out my velocity and trajectory, but i don't have a chrono. Any suggestions? Is the best way to figure out trajectory without velocity to just shoot a huge piece of cardboard and measure bullet drop at different distances? Is there a way to figure out velocity if you know bullet drop?

 

[kc0pph]

Mathematically yes if you know your BC, and at least 2 different locations of drop. You will need to know all of your environmental conditions as well.

Just buy a chrono they are under $100.

 

[AdamSmith007]

Mathematically yes if you know your BC, and at least 2 different locations of drop. You will need to know all of your environmental conditions as well.

Just buy a chrono they are under $100.

Well you should just buy me one then! Is there a formula or online calculator you know of? Thanks for your help!

 

[D.ID]

Yes, you can estimate velocity using a real world drop. I have a chronograph and do not bother to use it anymore. Save your money for ammo. As long as you know your bc, environmental conditions and zero you can easily use a ballistics program to establish velocity and trajectory. Get a four foot target and Zero your rifle dead on at a hundred, then move back to four hundred aim for the top edge of the target and shoot a group. Measure the drop, put the known factors into a ballistic program and adjust the velocity until it lines up with the drop. Then as always, confirm at longer distances and adjust if need be. I have found this method to be more reliable than chronographs anyway and since you always have to shoot to confirm real trajectory this is two birds with one stone. Basic algebra: using known factors BC & D = to establish V and calculate T. Make sure to check your scope tracking and you should be good to go.

 

[AdamSmith007]

Yes, you can estimate velocity using a real world drop. I have a chronograph and do not bother to use it anymore. Save your money for ammo. As long as you know your bc, environmental conditions and zero you can easily use a ballistics program to establish velocity and trajectory. Get a four foot target and Zero your rifle dead on at a hundred, then move back to four hundred aim for the top edge of the target and shoot a group. Measure the drop, put the known factors into a ballistic program and adjust the velocity until it lines up with the drop. Then as always, confirm at longer distances and adjust if need be. I have found this method to be more reliable than chronographs anyway and since you always have to shoot to confirm real trajectory this is two birds with one stone. Basic algebra: using known factors BC & D = to establish V and calculate T. Make sure to check your scope tracking and you should be good to go.

Thank you! This is very helpful!

 

[D.ID]

It is my not so popular opinion that the biggest deterrent for people getting in to long range is the elusion that you have to buy all this extra junk. You have to have a good rifle, ammo, scope, range finder and a range to practice at............. everything else is a convenience not a necessity.

 

[paphil]

There are several factors that are important when using a ballistic program to generate a drop chart. First and foremost , you cannot generate a good chart with inaccurate data. Your "o" has to be exactly on, be it 100 or 200 or 300. The distance to the targets must be exact, not 5 or 10 yards short or long. The atmospheric conditions, ie. temperature, altitude and barometric pressure must be precise. It is a simple thing to print out a generic drop chart using the mfg. BC and a guessed or chronographed velocity. This is just the first step. If you are shooting big game out to 500-600 yards, this generic chart will probably serve you well. If you want a precision chart, lets go to step 2! SHOOT YOUR DATA. your gun will be different than that generic chart. Using the generic chart as a guide, shoot at a mid range target and a long target. I usually start at 500 and then 700 and 950 and 1200 for my long target. I like to shoot a 4 shot group at each distance and record them carefully. It is not necessary to "O" at each range but we can calculate the true click value needed to be on at that range. If the generic chart says 16 clicks for 500 yards and my group is 5 inches high then I would record 13 clicks ( using 1/3 Moa clicks, I am 1 MOA high at 16 so 13 will be right on) Do this at each target and you have created your own ballistic curve for that gun. If you are using the Best of the west or G7 program here on the site , you now enter the long range data in the program and calculate. This will generate a chart that is much closer to your ballistic data. If you have a chronographed mv, float the BC. If not float the velocity before calculating. Now compare the data on this chart with your real data. The middle target data may be higher or lower than what comes up on the chart. By bumping the BC up or down .01 at a time and re calculating, your chart will come right in line with your real data. You will now have true BC and velocity for that bullet and a near perfect drop chart!

 

[AdamSmith007]

Ok i have my bullet drop at 300, 400 and 500 and i tried using the G7 program but it still needs to know the muzzle velocity which i don't know. Any help?

 

[D.ID]

Did you get t his worked out????? I do not know the program you used but if you run it threw a standard program like JBM ballistics and enter the known factors then adjust a hypothetical velocity until your drops line up in the real world it will show you were your velocity is at the muzzle and down range.

 

[AdamSmith007]

JBM only works on a PC, i have a Mac. I tried a couple other ballistic programs but am having difficulty. Maybe one of you guys can help.

Here is my info.
Hornady 55gr V-max BC=.255 i believe

Bullet Drop@
300 yds 9"
400 yds 25"
500 yds 50"

It was about 40 degrees F out when i shot and my elevation is about 2500.

 

[Scot E]

What is your scope height, zero distance, pressure and humidity?

Scot E.

 

[AdamSmith007]

No idea on scope height. How do I figure that out? I can look it up online too. Zero distance is 100 yards and I have no way knowing pressure and humidity. Sorry if I'm no help.

 

[paphil]

The best that I can come up with using what you provide is MV of 3311 and BC of .230 . As you can see the chart is off at 300 yards by 1 inch but the other ranges fall right in lineRange
(Yards) Vel. Enrgy Wind Def.
(MOA) Path
(IN)
0 3325.3 1350.2 0.0 -1.8
25 3219.2 1265.4 0.2 -1.0
50 3115.7 1185.3 0.5 -0.4
75 3014.8 1109.8 0.8 -0.1
100 2916.2 1038.4 1.0 -0.0
125 2819.8 970.9 1.3 -0.2
150 2725.6 907.1 1.6 -0.6
175 2633.3 846.7 1.9 -1.3
200 2543.0 789.6 2.2 -2.4
225 2454.5 735.6 2.5 -3.7
250 2367.8 684.6 2.8 -5.5
275 2282.8 636.3 3.2 -7.6
300 2199.4 590.7 3.5 -10.1 Off 1 inch
325 2117.8 547.7 3.9 -13.1
350 2037.9 507.1 4.3 -16.6
375 1959.8 469.0 4.6 -20.6
400 1883.6 433.2 5.0 -25.2
425 1809.3 399.7 5.5 -30.4
450 1737.0 368.4 5.9 -36.2
475 1666.9 339.3 6.3 -42.8
500 1599.1 312.2 6.8 -50.1
525 1533.8 287.3 7.3 -58.3
550 1471.2 264.3 7.8 -67.4
575 1411.4 243.2 8.3 -77.5
600 1354.7 224.1 8.9 -88.7

I don't know that your velocity is that high ,but the chart fits, wear it!

 

[AdamSmith007]

Thanks Phil! I appreciate you and everyone else taking the time to help! I finally was able to find a ballistics calculator online that worked and with that calculator i too am finding that my 300 yard is 1 inch high, but 400 and 500 are right on. The hand loads i was using for my test were not the most accurate. My powder measurer is inconsistent and i didn't take the time to weight each charge, so i think my drop data could be slightly off.

Anyway, this gets me close! Thanks again!