Matching verified dope to ballistic software dope

[Kramerica]

You need to get an average of at least 10 shots for the velocity, not just 1 or the fastest. And, are you calculating the actual muzzle velocity or just what reads on the chrono? The actual muzzle velocity could be from 5 to 10 fps faster. Look up the specs on your chrono and see what the margin of error is. Are you using G1 or G7 BC figures? Use G7 if you have the option. No program is going to be 100%. You'll need to adjust your inputs and see if it helps. Velocity will have more of an impact closer and BC farther out. It may be a balancing act between the 2 to get a little closer. Are you sure of the distances? At 600 yards with that slow of an MV, the bullet will be coming down at a pretty good angle. If you miss the distance even a few yards, it will either hit higher or lower.

That was the average of 4 shots. Although as I previously stated I don't have the utmost confidence in that old chronograph it's all over the place, with all kinds of ammo and different rifles. If I can find the g7 I use that if not I go with the g1 as it's usually easier to obtain. Haven't had a chance to get back to that range to verify the distances. Hay is getting to high to see the targets and it's been to wet here to bail it. I'll post the results when the hay is cut and I can make it back out.

 

[T-shooter]

That was the average of 4 shots. Although as I previously stated I don't have the utmost confidence in that old chronograph it's all over the place, with all kinds of ammo and different rifles. If I can find the g7 I use that if not I go with the g1 as it's usually easier to obtain. Haven't had a chance to get back to that range to verify the distances. Hay is getting to high to see the targets and it's been to wet here to bail it. I'll post the results when the hay is cut and I can make it back out.

If you have a friend with another chrono, set them up end to end and shoot through both at once. The readings should be similar or at least vary by about the same amount.

I'm waiting on the corn to grow. Later in the season I'll have a 12'-14' wide shooting range/path 215 yards long with 7'-8' high corn as a wind break on both sides. Nice except for the insects.

 

[T-shooter]

I am shooting a RPR 6.5CM, with a NF ATACR 5-25 on top. Sight height is 2.69". Using factory Nosler 140 BT ammo. BC is .509 I believe if I remember that correctly. My velocity I got using an older F-1 chrono was 2473 fps ( yes I know that's slow). Chrono could be off. Shots sub moa at 100 consistently. I got a chance to verify my dope at 600 yards and 300 yards it turned out to be 4.5 mils and 0.9 mils respectively. I cannot get the dopes to match up in JBM or iSnipe. I can obviously get one of the yardage settings to line up but cannot get both together. I messed around quiet a bit with both the BC and velocity in the ballistics programs with zero luck. Any advice is appreciated.

Here is a free program to back calculate the muzzle velocity. Fill all the fields like any other and set your first output field at 3 or 4 yards. I use 4 and place my chrono 12' out. Under SELECT / CARTRIDGE you can vary the velocity input and watch the velocity 3 yards out. This should get you in the ballpark. My 208g .308's only lose about 5 fps at 3 yards. Some others will lose 9 to 12 fps.

http://www.modernballistics.com/download.htm

I just ran my specs on 3 different free ballistics programs. Long Range Hunting (G7), Hornady 4DOF, and Applied Ballistics. Actually pretty close numbers between all 3 using G7 specs and calculating for spin drift and Coriolis at 1,000 yards:

LRH Drop= 395.10" Total windage (no wind)= 11.50" Velocity= 1,322 fps

Hor Drop= 391.14" Total windage (no wind)= 9.92" Velocity= 1,324 fps

A/B Drop= 393.63" Total windage (no wind)= 10.43 Velocity= 1,325 fps

 

[Kramerica]

Here is a free program to back calculate the muzzle velocity. Fill all the fields like any other and set your first output field at 3 or 4 yards. I use 4 and place my chrono 12' out. Under SELECT / CARTRIDGE you can vary the velocity input and watch the velocity 3 yards out. This should get you in the ballpark. My 208g .308's only lose about 5 fps at 3 yards. Some others will lose 9 to 12 fps.

http://www.modernballistics.com/download.htm

I just ran my specs on 3 different free ballistics programs. Long Range Hunting (G7), Hornady 4DOF, and Applied Ballistics. Actually pretty close numbers between all 3 using G7 specs and calculating for spin drift and Coriolis at 1,000 yards:

LRH Drop= 395.10" Total windage (no wind)= 11.50" Velocity= 1,322 fps

Hor Drop= 391.14" Total windage (no wind)= 9.92" Velocity= 1,324 fps

A/B Drop= 393.63" Total windage (no wind)= 10.43 Velocity= 1,325 fps

Sweet! Thanks for the link, I'll check it out