Calculating range adjustment for ranges you have not shot?

[Canhunter35]

What bullet is this for? If u really doubt the advertised bc you can use Litz bc likely

 

[338 dude]

Hmm ok I'm confused. For example I know my muzzle data is spot on cause I'm using magnetospeed but what if the bullet manufactures BC is slightly off which is causing a slight issue. How would you compensate for the other ranges without shooting them?

What bullet what caliber are you shooting

 

[dfanonymous]

I want to know why BC is going to matter at borderline PBR range. Unless you are shooting a .22lr, BC doesn't take a huge or at all effect at these ranges. Your BC is going to matter at transonic/subsonic range. While the bullet is going supersonic, you need to true the muzzle velocity to align the software.

As far as BC is concerned, the advertised BC are averages. There is a dead nuts on BC value per mach change. So in theory, say you G7 value is .250, people can give you .255, .245 .242 and all these BC's would be correct depending MV decay obviously, it would be at a lower mach, and thus the BC would be on the lower side of the spectrum, and it still won't matter more than MV at 600y and in because that decay isn't significant enough. This is why applied ballistics makes you true MV around transonic.

 

[BrentM]

Good question. So generally if a dial in is not matching the solution then clearly something is not correct in the ballistic inputs.

If youR dial to is 10 to be on target but the solution is 10.5, I'd take off .5 for the other ranges and send it. If this compensation is off or not correct then it's usually one of these: scope height, scope tracking, incorrect atmospheric data, g7 vs g1 numbers are reversed, parallax. For these shorter ranges FPS and bc will not give much error unless way off. I highly doubt you are way off.

 

[rustyshackleford]

All,

my back yard range goes to about 300 yards however o have one spot where I can shoot 600 yards now. This is ONLY 600 yards due to obstructions and rolling hills. I have used jbm ballistics to calculate estimates for blank range but never for actual dialing in. So my question is let's say you worked up a load andthe ballistics program says dial up 10moa for 600 yards but you find out you actually need to dial up 10.5 or 9.5 or some other number. How can you take that info and back calculate for 500 and 400 yards etc?

If you are shooting a bullet with a litz measured BC and your simulated drop doesn't match what you encountered you put in bad data somewhere. Just recently I shot a non-sanctioned rifle match out to 800 with a load I never shot past 100 and my 800 yard drop was dead nuts. The morning of the match I adjusted my model using weather data from the nearest station for barometric pressure. And this data was generated using JBM trajectory simplified

 

[DavidleeCole]

Run a box drill with your rifle at 100 yards measured to the exact. Track your scope and then measure the exact point of impact of each dialed group. Next use exact MOA to inches or Mil to inches which ever your scope is and convert exactly how much the rectical moved point of aim to how much point of impact moved and find the difference. Next divide that distance by number of dialed distance in clicks. you may find a small inaccuracy in the scope which you may not realize at close distance but will become larger the further you shoot. This will give you a tracking value you can use at longer ranges to be more on target due to scope reticle tracking inconsistency. This will remove that from the equation. After that I would look at my muzzle velocity BUT CONSIDER THE EQUIPMENT FIRST. My scope has around .01mill per 10 mils. So that puts my point of aim and impact slightly off at longer ranges. No problem cause you use the value to figure in with your dope and your back on target. FIND OUT WHAT RANGE THIS WILL EFFECT YOU THE MOST AND THEN WORRY ABOUT CORRECTIONS. IE at 600 yards I am 3 inches off,

Deer or Elk no problem just shoot. Prairie Dog or a match figure the correction and stay on target. Bryan Litz, Applied Ballistics books are wonderful information and good reads. BE SCIENTIFICALLY MINDFUL AND FIND THE REASON FOR WHAT IS HAPPENING. Hope this was helpful.

 

[gohring3006]

Put a large target at 600, shoot for dead center at 300 then shoot for dead center at 600 without dialing the scope. Measure the drop and enter velocity scenarios in your calculator to match the drop. BC is only a input for the calculator at this range, it's not going to matter much.

 

[Bigeclipse]

Good question. So generally if a dial in is not matching the solution then clearly something is not correct in the ballistic inputs.

If youR dial to is 10 to be on target but the solution is 10.5, I'd take off .5 for the other ranges and send it. If this compensation is off or not correct then it's usually one of these: scope height, scope tracking, incorrect atmospheric data, g7 vs g1 numbers are reversed, parallax. For these shorter ranges FPS and bc will not give much error unless way off. I highly doubt you are way off.

This is what I was looking for. Thank you. I do have a question about scope height. Do you measure from bore centerline to scope bell center?

 

[JAYgs8163]

Maybe I'm Confusing people. I haven't shot the 600 yards yet. I was curious that since I can only shoot to 300 and then 600...if 600 is slightly off how can I feel confident about drops at 500 and 400 should I go hunting at the ranges without actually shooting those ranges. So let's say jbm states 10moa adjustment. I shoot at 600 and see I need a bit more like maybe 10.3moa. How do I know what 50 would now be?

You can't be confident to shoot at 500 and 400 until you shoot at those ranges. The app is not the end all tell all. If you're off a "little" at 600 it should be off less at 500 and even less at 400. You need to shoot at those ranges and get the hard data. Best suggestion would be leave your backyard range and go somewhere you can shoot 400, 500, 600, 700, ...... don't rely on the app, your input data, the bullet mfg stated bc, without verifying everything first at the range. Especially, in a hunting scenario. Good luck.

 

[lyle2231]

All,

my back yard range goes to about 300 yards however o have one spot where I can shoot 600 yards now. This is ONLY 600 yards due to obstructions and rolling hills. I have used jbm ballistics to calculate estimates for blank range but never for actual dialing in. So my question is let's say you worked up a load andthe ballistics program says dial up 10moa for 600 yards but you find out you actually need to dial up 10.5 or 9.5 or some other number. How can you take that info and back calculate for 500 and 400 yards etc?

Call Sierra bullets! Ok so you're not shooting Sierra but they're data base is quite extensive. Just tell the tech what bullet weight and whether flat base or boat tail. All the bullet manufacturers have help lines.

 

[Bravo 4]

Ballistic Program Inaccuracies

Read this link. You don't have to agree with all of it, but it can point out several possible discrepancies.

 

[dm406]

Maybe I'm Confusing people. I haven't shot the 600 yards yet. I was curious that since I can only shoot to 300 and then 600...if 600 is slightly off how can I feel confident about drops at 500 and 400 should I go hunting at the ranges without actually shooting those ranges. So let's say jbm states 10moa adjustment. I shoot at 600 and see I need a bit more like maybe 10.3moa. How do I know what 50 would now be?

doesn't matter, won't be far enough off to miss in a hunting situation

 

[Bigeclipse]

You can't be confident to shoot at 500 and 400 until you shoot at those ranges. The app is not the end all tell all. If you're off a "little" at 600 it should be off less at 500 and even less at 400. You need to shoot at those ranges and get the hard data. Best suggestion would be leave your backyard range and go somewhere you can shoot 400, 500, 600, 700, ...... don't rely on the app, your input data, the bullet mfg stated bc, without verifying everything first at the range. Especially, in a hunting scenario. Good luck.

I'm in NY. There are zero ranges near me which allow over 300 yard shots. If anything I have people bothering me to shoot 600 at my house. I may have to take a trip I guess somewhere I can shoot those distances.

 

[JAYgs8163]

I'm in NY. There are zero ranges near me which allow over 300 yard shots. If anything I have people bothering me to shoot 600 at my house. I may have to take a trip I guess somewhere I can shoot those distances.

A little weekend shooting trip is always good for the soul. Go do some 1000 yard social distancing. Google earth sometimes offers some help in spotting locations. Look for logged out areas that've been clear cut. Power line cuts, etc.... my father lives in Maine and had the same issue. We found him some nice logged out clear cuts, he can touch out to 850 there. He's 81 and still making it happen. Speaking of Maine the Moose lottery draw is today. Good luck and hope you find somewhere. I'm in Az and drive 2 hours each way to my preferred shooting area.