I've been trying my hand at longer range shooting (300 to 400) yds for me. I've noticed that the "Point Blank" software I use it not that close to real world experience. It's possible that my zero is a little off on the 22-250, but not more than .5 inches. The 6mm BR is dead on @200 yds. I know my shooting might not be the best, but all groups were under .75 MOA with the 22-250 and under .5 MOA with BR.

Examples:
22-250, 50 vmax, ~3800 fps
200 yd zero shows 4.81 drop @300 and 14.83 drop @400 yds
Range shows 2.25 @300 and 12 @400
Doesn't matter if I increase the velocity or change scope height in the program, still can't get to those nbrs.

Second Example
6mm BR, 90 Berger match, ~3100 fps
200 yd zero shows 6.31 drop @300 and 18.58 drop @400 yds
Range shows 3.75 @300 and 14.45 @400

I didn't expect the software to be perfect, but closer than that. What am I doing wrong here. It's physics, bullet weight, BC, and velocity should give me a close answer here. I know that scope height and elevation can play a factor, but not this big.

How accurate are your velocities?
Are you using muzzle velocity or 10 to 15 feeet from the muzzle?
your scope may track diffrent from your -0- to 600 yrs.
The clicks may not be true moa.
what size groups are you getting at 400yrs? are they moa?
Dave, just guessing.

One of the big varibles is your rifle but I think everyone agrees that the only real way to tell what your rifle will do at 300 yards is to shoot it at 300 yards.
I wouldn't angst about it too much and use your program as a guide rather than trying to use it as an absolute.

quote:

Originally posted by jb177:
I've been trying my hand at longer range shooting (300 to 400) yds for me. I've noticed that the "Point Blank" software I use it not that close to real world experience. ...

Hey jb, Good on you for doing the actual verification. Whoever gave you the idea that the External Ballistice Software - from any company - is accurate was/is full-of-beans.

They just get you "close" because of all kinds of things that can't be accounted for in the Software.
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However, if you do want the Computer Generated(guessed at) Trajectory closer to reality, vary the Ballistic Coefficient in the Formula. But even if that gets you tracking properly at 400yds, don't automatically deduce that the "guessed at" trajectory will be accurate at 600yds, 800yds etc.

Just as you discovered, you always have to create an accurate Drop Chart by doing the actual shooting at the distances you want to take a shot.

Nice catch on your part. Best of luck to you.

HC beat me to it, external ballistics involves 3 basic items: muzzle velocity, barrel/sight plane angle (launch angle) and BC.
You know your velocity
The angle is consistent
The only "unknown" is the actual BC (using the correct G form).

I like to use a "bullseye" hold and fire on targets at 100yd intervals from 100yd to 500yd and than measure from the aiming point to the center of the various groups. Now, adjust the BC until the "computer curve" closely matches the actual flight curve.

Thanks for the input.

As for the velocities, it wouldn't matter if I was off 200 fps, the nbrs still don't jive. I was using 2 different scopes (nikon monarch and elite 4200) with 1/8 inch clicks. The groups were good enough to prove to me.

I was just hoping for something a little closer to reality so that I could be on paper at 600 yds without having to walk it all the way out there.

quote:

Originally posted by jb177:
...I was just hoping for something a little closer to reality so that I could be on paper at 600 yds without having to walk it all the way out there.

Get a Refrigerator Box or Mattress Box and tape the Target to the Top.

Just as Tailgunner said, measure down to the center of each shot(from a straight line) and average the value.

The Kick-in-the-Nose, is that Sierra is correct in their Manuals about the B.C. changing as the Velocity Degrades. So, unless the Math Models(Software) account for the change, they still won't be quite accurate.

As a Major Benefit, the more you actually shoot at distance, there is a HUGE Ballistics knowledge increase compared to up close shooting. It's not all about Vertical Clicks.

Basically it makes you wonder how many shots it takes to get good enough to hit things with the First Shot way out yonder. You are on the right track.

Best of luck to you.

quote:

Originally posted by Hot Core:
Hey jb, Good on you for doing the actual verification.

They just get you "close" because of all kinds of things that can't be accounted for in the Software.
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Just as you discovered, you always have to create an accurate Drop Chart by doing the actual shooting at the distances you want to take a shot.

Nice catch on your part. Best of luck to you.

Right on, Hot Core.

Also, from my years shooting DCRA full-bore competition, and Palma matches, let me add that one's drop chart may also vary conspicuously depending on WHERE you are shooting, the elevation, the weather, and so on.

For instance, my "Dope Book" for shooting at the Palomino Range in Calgary, Alberta, differed as much as 2-1/2 minutes from my zeros for shooting at Connaught, Ontario (both places with me shooting at 800, 900, or 1,000 yards, with the same ammo and rifle). Part of that was temperature, part humidity, part elevation, and part who-knows-what.

Anyway, it was important because in those days at least, the DCRA allowed two "convertible" sighters at the beginning of each match. That is, If your first "Sighter" was a "V-Bull-5", you might consider "converting it from a Sighter to a "Recorded Shot on score". If the second sighter was also a Bull-5, V or not, you would almost certainly want to have converted them both. In a 15-shot match, then you would only have 13 shots more to fire, which would cut down on the fatigue factor or chances of conditions changes and give you a better chance of "going clean".

Trick was, you had to decide immediately after each shot if you wanted to convert it or not. So, if your first shot wasn't a good, called, "center V-bull", you might not want to keep it as a record shot if it was just a "nipper" bullseye. There would be too much chance the next shot would be an "Inner-4" or even a "Magpie-3'.

At any rate, if you took the first Sighter as a converted Record Shot, you had to do the same thing for the second Sighter too, as your "record string" started with the first sighter you converted (if any).

Long way of saying your dope book had to have GOOD data specific for wherever you shot in whatever weather, if you wanted the first TWO sighters to be converted to your advantage.

I still have the same rifles, some of the same ammo, and my dope book just in case I ever HAVE to make a first round hit at some real threat, way out there. Not likely, but the right stuff is still available...

So, a really useful dope book (drop chart) should not only include actually fired data, but the conditions under which it was fired. (At minimum: rifle, ammo, altitude, temp, and humidity).



BTW: Yes, fellow Canucks, I am aware that ranges in Canada are now at metric distances. The era to which I am referring was previous to the change to metric.

Guess I need to find a longer field to shoot in. 500 is about all I can get where I'm at. I really want a 500 yd pdog this summer, be great to get it on my first trip ever. Wind will be my biggest obstacle of course, dialing elevation should be the easy part.

Anybody know of any software that is closer to real-world drop? I'd like something that would get me at least 1 MOA from bullseye.

jb.


http://www.eskimo.com/~jbm/calculations/traj/traj.html

This got me inside 3" @ 600 off the bonnet with a bipod

l was using my 7-08rem 24" bbl @ 2800fps 130smk load. At 250yrd i can hit 1" easy if I doo my bit, and that's off the data sheet..... Bloody well impressed me!!!

Drag Factors

For those who require drag factor data for Ballistic Programs.

For use where “G†= Drag factor.

G1. Standard model flat base, pointed bullets 3.28 cal’ in length with 1.32 cal’ length nose. + .2 cal’ blunt ogave.

G2. Long conical point 5.19 long .5 cal’, 6 O/ boat tail not applicable to small arms.

G5. Moderate (low base) boat tails, 7 O/ 30cal’ taper with 6.19 tangent ogave.

G6. Flat based, Spire point bullets, 6.9 cal’ long with secant ogave.

G7. VLD’s with long 7O/ 30 cal’ tail tapers + 10 cal’ tangent nose ogave.

G8. Flat base with similar nose to G7, 3.64 cal’ long with 2.18 long nose + 10 cal secant ogave. USMC 152grn .30 cal’ match’s this drag factot

Good luck and good shooting mate.

Dave.
....

I'm not sure whether the change in BC would cause that large a difference. I suspect that the biggest variation is due to height of the scope above the barrel. All charts state what the dependency is, generally 1 1/2 inches above the barrel. A large objective, plus extra high rings couls easily give you 2 inches above.
Peter.

Concur with Peter, For most any ballistic calculator to be correct the height of the scope (center of tube) must be measured correctly above the center of the bore. Having this coreect gives the program a correct angle of departure. Small differences in that angle caused by incorrect measurement can greatly effect the results at longer ranges. The use of "1.5" inches for this figure only works if the height rally is 1.5". Otherwise the use of that arbitrary 1.5" will only get you close.

Larry Gibson

Maybe the software I am using doesn't calculate correctly based on scope height b/c changing it from 1.5 to 3.5 only changed the drop 2 inches at 400 yds. Not sure exactly what my scope height is, but it's mounted as close to bore as possible for 40 mm scope (medium rings).

quote:

Originally posted by jb177:
I've been trying my hand at longer range shooting (300 to 400) yds for me. I've noticed that the "Point Blank" software I use it not that close to real world experience. It's possible that my zero is a little off on the 22-250, but not more than .5 inches. The 6mm BR is dead on @200 yds. I know my shooting might not be the best, but all groups were under .75 MOA with the 22-250 and under .5 MOA with BR.

Examples:
22-250, 50 vmax, ~3800 fps
200 yd zero shows 4.81 drop @300 and 14.83 drop @400 yds
Range shows 2.25 @300 and 12 @400
Doesn't matter if I increase the velocity or change scope height in the program, still can't get to those nbrs.

Second Example
6mm BR, 90 Berger match, ~3100 fps
200 yd zero shows 6.31 drop @300 and 18.58 drop @400 yds
Range shows 3.75 @300 and 14.45 @400

I didn't expect the software to be perfect, but closer than that. What am I doing wrong here. It's physics, bullet weight, BC, and velocity should give me a close answer here. I know that scope height and elevation can play a factor, but not this big.

Since your rifles seem to be shooting a slight amount flatter, considering the range involved, I would hazard a guess that your scopes' line of sight axes are just a very little bit higher than that allowed for in the ballistic software.