Ballistic charts and drop, need help...

[Evil_Dark]

here is your first problem.........your range has the following

100 yard target frame
200 yard target frame
300 meter target frame
500 meter target frame
600 yard target frame

without a proper laser range finder on that range your never going to know what it is your trying to accomplish. still doesn't account for alot of your errors but knowing the target distances will take some of the error out and get you closer.

I was knowing my target distance at 0.5 yards accuracy... Why do you doubt about it? Probably my poor english mistaken you?
I'm shooting in our familly land for 10 years now, at the beginning I did measure the 100 yards increments with a tape. The max range that I can shoot is 500Y. Shooting on the neighboor field (when the crops are gone) permit me to go 785 yards. But I have to walk to my target Instead of using my vehicle.

Dark

 

[yodave]

I was knowing my target distance at 0.5 yards accuracy... Why do you doubt about it? Probably my poor english mistaken you?
I'm shooting in our familly land for 10 years now, at the beginning I did measure the 100 yards increments with a tape. The max range that I can shoot is 500Y. Shooting on the neigboor filed (when the crops are gone) permit me to go 785 yards. But I have to walk to my target Instead of using my vehicle.

Dark

sorry, assumed you were still shooting at the CR range

 

[Evil_Dark]

Yes, BC is a moving target... Bore roughness, number of lands and grooves and how that engraves in the bullet, muzzle velocity, twist rate, mag feeding damage can all affect the ACTUAL real world flying through the air BC. Even ambient conditions can have slight affects on this ...

Jerry

Ok, I understand, Pretty logic. Thanks for the clarification

Dark

 

[Mystic Precision]

I enjoyed a read on the then new Oerlikon (sp?) anti aircraft gun many years back.

To make sure the bullets would make it to target, the muzzle velocity was measure in real time as the gun fired then a radar would track the bullet to gain the BC in flight and then all this would be crunched through the computer to get that line of bullets onto target.

The big boys have known about this for a very very long time.

Jerry

 

[IMR4320]

I see a few things here. I shoot the same Hornady bullet but I use Hornady's correct data, which is BC G1 @ 0.450 for this bullet. Your humidity seems a little low at that temperature but should not affect your ballistic all that much. Your biggest problem to me seems not really have established zero. You can zero it at 100 but for all practical purposes, 200 is a lot more practical. Then you also mix meters and yards, while that does not matter all that much at 100 or up to 200 or so, it will definitely be an issue at 300 and farther, since 300 yards is 273 meters and 300 meters is 329.6 yards. Now your ballistics will be affected. Get into unified system, either yards or meters, it does not matter which all that much, although for MOA units, yards work better. Then zero your rifle to 200 as the most practical range and put all of that data into JBM calculator with 10 meter or yard increments and get your drop table. I would also expect your velocities a little higher but that depends on your barrel length and your ammo load.

 

[schumy]

Yes, BC is a moving target... Bore roughness, number of lands and grooves and how that engraves in the bullet, muzzle velocity, twist rate, mag feeding damage can all affect the ACTUAL real world flying through the air BC. Even ambient conditions can have slight affects on this (yes, the programs try to adjust for this in the math IF you can input good info)

best part... as your bore wears and affects the bullets differently, the drop chart will need tweaking (either caused by a change in bullet drag and/or muzzle velocity)

BC is most definitely not a fixed number even from the manf of the bullets... lot to lot variation can and does affect the shape you get in the box... just compare meplat diameters from lot to lot of the same bullet. Berger is one of the best for keeping up with current lot data... and if you track their BCs, they most certainly change them from time to time.. Smart for them and a great service to us shooters.

So I always get a giggle when shooters swear that this bullet must do XYZ and their program will give them accuracy to a 1/4" at 1 million miles. Shoot some bullets and you will quickly see what I mean.

Hell, take the same box of bullets .... load them in a few rifles at similar muzzle velocities and group them on paper at LR.. see what you get.

Being involved in Team shooting with what should be near identical set ups, we always have to tweak what actually happens on target cause things are never perfectly identical. Small adjustments.. sure, but adjustments never the less.

But the solution is very simple.... I print my drop chart and then mark in the corrections I need for my set up. Confirmed over many trips at multiple distances. This was confirmed with my rangefinder, my scope, my ammo, my rifle, my shooting, my real estate. Did I get dead reliable and repeatable drop charts to within 1/4 min out to 1000yds... YEP.

Can you take this data, enter it back into the ballistics software to "tweak" the values so it matches... you can now... and once you do, the software will adjust these tweaks as you go to different locations. So you are creating perfectly "flawed" results that suit you and your set up precisely.

Would it work for another rifle using the same cartridge and bullet.... maybe, but I wouldn't bet a double double on it

Jerry

I always learn something when you post Jerry, thank you for sharing with us!!