From the reading of so many posts about discrepancies in downrange figures from different programs ( commercial or free ) and being myself involved in the development of another package (now in beta) I asked myself : do we need to compute values beyond the 2000 yards mark?

While with my own knowledge and experience in LRH and ballistics fired a fast answer that doing so is futile due to innacuracies in the math models, especially at the transonic level, and not counting shooter's error at that distance and the almost ever present wind, my guess is that we cannot trust or need to push the envelope that far. Maybe for marketing reasons.

We have different drag models, differents algorithms, different books...(Pejsa, McCoy, just to name a few) etc, but so far I've never obtained from a certified source a true table showing real vs. predicted values. Not even in military circles, except ( and cannot confirm ) the ones involved in the CheyTac system.

Moreover, if we take that project into the scene, I've never found any proof of some claims ( and please do not take this statement as it not being possible or unreal )

In short, when some programs shows downrange values beyond 2000 yards, my best educated estimate is that they rarely are confirmed by real firings.

A couple of weeks ago I had the opportunity to check during a sniper exercise (Marines' Special Forces) under "somewhat" controlled conditions and up to 1200 yards the values I'm obtaining from my software.

Well, fortunately drop values were almost near the 99% of the threshold of accuracy ( field data vs predictions ) but when I tried to push the range out to 2000 yards, an experienced officer and a LRH himself, pointed out the many variables involved that otherwise can put in jeopardy a military operation, by not hitting the target with the first or two rounds. Beyond that they call in close air support

So, they don't need or foresee a future need for tables beyond that range. That prompted my original question posted here.

In short, I'll like to hear from more experienced shooters waht they think on this subject.

Thanks in advance!

It would need to go past 3500 yards if you want to sell it to me (my current project will need it), and have inputs so actual wind deflection can be obtained, (CP to CG correction factor).

In real ops, CAS is called in for the vast majority of things past 800 meters. Anyone who tries to make first round hits with software past 1500 needs to drop the crack pipe. Where the software is truly useful is that is vastly speeds the collection of real world data and makes it simple to back from real world data to actual B.C.'s as the B.C. changes during flight. When collecting data at extreme ranges in the real world, one is instantly confronted with the bullets B.C. changing while the bullet is in flight. Some bullets go up in B.C., some go down. Some go up, then go down. Some go up then level off, then go up again.

One must get multiple B.C. slots at various velocity that are user controlled.

S1,

Maybe you can share some tables of predicted vs field data? I'm most interested in your experience on this matter. Specially from your point of view regarding the use of ballistics programs. In other words it's interesting to me to compare more values against my software (now in beta)

Of course, I'm not here to make stupid claims on accuracy, since my model follows what is common in the industry on ballistics models, but with some modifications in the algorithms.

My post indicated that the output generated from many programs have huge differences in some cases before the 1000 yards mark! then my question...which one you trust the most?

If you have the will, I'll put my time to collaborate with you in order to develop a good package, suited for LR.

As per the CP/CG components to estimate wind deflection, I guess you have a solid model of your bullets design, otherwise it'll be useless.

Not just a model, real world data. The biggest problem that I have run into is wind deflection estimates. The software must separate B.C. data use for flight time and then subsequent trajectory calculations from wind deflection calculation based principally on flight time.

Lets take two different bullet designs that have been synchronize fired with shutters and return to battery weapons side by side and under identical conditions in a full value 10 mph crosswind.

The first bullet a 175 Sierra Matchking in 308 fired from a 7.62 Nato chamber at a muzzle velocity of 2,640 fps. to a target at a range of 600 yards.

The software I used to use says 30.5 inches of wind deflection, 122 inches of boreline drop, and .8553 seconds of flight time.

The actual wind deflection was around 26 inches, actual borline drop 123 inches, and actual flight time was .8712 seconds.

In this example the errors in the projections for drop and flight time were less than 3 percent. The error for projected wind deflection was over 17 percent of actual.



The bullet synchronize fired next to this bullet is a 200 grain high density core bullet with an average B.C. of .685 fired from a 30 Wolf at 3,280 fps. The software projects the wind deflection to be 15.3 inches, the borline drop to be 70.8 inches, and the flight time to be .6350 seconds.

Actuals are 7.7 inches of wind deflection, borline drop of 68.5 inches and a flight time of .6354 seconds.

Once again the wind deflection estimate is deplorable, but this time the error is extremely large. Thus the problem with improved bullet technology when using computers.

S1, please could you add more data, specially at longer ranges? If possible up to 2000 yards.

I assume Army standard conditions for pressure, temp and humidity. Is this correct?

It also will be helpful to know from which model or software are you generating those values, since I'm trying to reproduce them as accurately as possible.

And yes, wind deflection is another game...

Thanks for the input

When I get some spare time, I will send you more data. Is your email still good?

quote:

Originally posted by S1:
When I get some spare time, I will send you more data. Is your email still good?

Thanks again for your great cooperation on this subject!

Yes, my listed email is Ok

regards, G