Math Experts

H

HOGGHEAD

New member
I need help with a little math problem. I have not figured out a math problem like this since college. And that was well over 30 years ago. So I need a little help.

I want to calculate how high my bullet is hitting at 100 and 200 yards with the following data.

1. Bullet is a 75 grain A-Max with a BC of .435 in a 22-250.

2. When I did my load data the only distance I shot was 300 yards. I prefer to check my loads at longer distances than 100 yards. 300 yards is a great distance. You can really sort out the loads as long as you can call the fliers.

3. The rifle is sighted dead on at 300 yards. And shooting unbelievable groups at that distance.

4. Scope is a 6.5X20 Zeiss Conquest with TT's. The scope adjustment is 1/4 MOA per cick.

5. I also shot the rifle at 400, 500, and 600 yards. But not enough at 600 yet to get a perfect zero.

6. At 400 yards I need to raise the scope 9 clicks to change the zero from 300 to 400 yards.

7. At 500 yards I need to add 7 more clicks to the 400 yard zero to hit dead on at 500 yards.

8. So I have a total of 16 clicks to raise the zero from 300 to 500.

9. I want to leave the scope zeroed at 300 yards then dial in my 400 and 500 yard shots.

According to my reloading data my load should be about 3200 fps. But I did not chrono the load. So I do not know that for sure. The barrel on my rifle is 28", so the loads could be a little different.

What I would like to calculate is when my rifle is zeroed at 300 yards. What will be my point of impact be at 100 and 200 yards.

Now I realize it would be easier to go to the range and just shoot the rifle at 100 and 200 yards. But that is not an option right now. I want to take the rifle hunting and since I am handicapped I can only get out once or twice a week. So my options are to go hunting a day or two or take a day off ground hog hunting and take another day to the range. I would prefer to hunt, but I would really like to know where my bullet is impacting at 100 and 200 yards.

Do I have enough information to calculate that?? And if so then what would that trajectory be?? I did try to enter some numbers into a ballistic calculator, but I did not do so well. Thanks, Tom.
 
Last edited:
You need to add into your calculations the scope height and velocity. That will make a difference as well. Free ballistic programs online will help you see the trajectory with a graph. It should get you close
 

I was hoping someone would have a formula or know how to figure the trajectory backwards from the information I provided. If not then I understand. And it is really not that big of a deal. I was just curious if someone knew how to figure it out??

I wanted to make this a fun topic and see how smart some of you guys really are. And then you could show me how big of a dumbie I am. Tom.
 
Last edited:
Tom, What is the caliber (scratch that,,, I see it..) and scope height...?? I'll try to crunch some numbers and see what pops up..
 
Last edited:
I am not exactly sure of the scope height. The scope has a 50 mm OL and sits very close to the barrel. However the barrel is a full bull Krieger barrel. And very long. So I am not exactly sure. Your guess would be as good as my ability to actually calculate the height. Or is there a good way to do it?? Thanks, Tom.

005-3.jpg


001-7.jpg
 
Okay,, Here's what I come up with...9 clicks on a 1/4" turret should raise your point of impact 9" at 400 yards...

If I feed all the other variables into the ballistic program, assuming that your velocity for that round is 3200 FPS, that will give you a drop of 9.2" at 400 yards if zero'd at 300 yards...Not sure I can come up with the exact velocity to remove the .2" at 400 yards...

Your point of impact at 100 yards should be +3.2" and at 200 yards, +3.9" for the 300 yard zero...

Hope this helps...
 
My comment was that by knowing the powder and weight of the bullet. barrel length you were using, that you prolly had a ballpark figure on the velocity. Carry on.
grin.gif
 
Originally Posted By: OldTurtleOkay,, Here's what I come up with...9 clicks on a 1/4" turret should raise your point of impact 9" at 400 yards...

If I feed all the other variables into the ballistic program, assuming that your velocity for that round is 3200 FPS, that will give you a drop of 9.2" at 400 yards if zero'd at 300 yards...Not sure I can come up with the exact velocity to remove the .2" at 400 yards...

Your point of impact at 100 yards should be +3.2" and at 200 yards, +3.9" for the 300 yard zero...

Hope this helps...



So you are saying my 3200 fps velocity guess is pretty close?? Tom.
 
The real reason I started this thread is because when I match the numbers in the ballistics calculator that I use I keep coming up with a velocity of 3400 fps. And I did not think you could get 3400 fps from a standard 22-250 with the 75 grain A-Max.

However when I punch in the 300, 400, and 500 yard zero my drops almost exactly matchs the "calculated" ballistics of 3400 fps.

Now this is not theoretical drop. It is the actual drop that my rifle is shooting. And those are the actual amount of clicks that it takes to zero at 400 and 500 yards.

Can this be?? Can I be getting 3400 fps from a 75 A-Max in a 22-250. I know the actual facts sure support that. I wish my chrono wasn't broken. Tom.
 
Originally Posted By: Orneryolfart357My comment was that by knowing the powder and weight of the bullet. barrel length you were using, that you prolly had a ballpark figure on the velocity. Carry on.
grin.gif



Actually you are correct about that. But the only problem is I keep coming up with a velocity of 3400 fps with the ballistics calculator I have been using. And I really did not think that 3400 fps was possible in a standard 22-250. So I was trying to see if someone could verify what I came up with??

And when using the powder load data the velocity should be coming in just under 3200 fps. However I do have a 28" barrel on the rifle. I was going to sell this rifle, but if I am getting 3400 fps with that bullet then I am probably going to keep it for a ground hog hammer!! That bullet should be extremely deadly on ground hogs at that velocity. I will probably have a short barrel life, but I can live with that!!
thumbup.gif
Thanks, Tom.
 
Last edited:
Originally Posted By: Orneryolfart357If your range supports a 100 yd target.. why not try it out measure it and remove all doubt?


Absolutely. I would realy like to do that. And I will do that. Only problem is my leg only alows me to get out once or twice a week, so I want to save those trips to the ground hog fields. However I definitely think I will put a couple shots down range at 100 yards when I get to go hunting. But if that is correct then 3400 fps with the 75 grain bullet is SMOKING!! This should be fun. So much for barrel life?? Tom
 
Originally Posted By: HOGGHEADThe real reason I started this thread is because when I match the numbers in the ballistics calculator that I use I keep coming up with a velocity of 3400 fps. And I did not think you could get 3400 fps from a standard 22-250 with the 75 grain A-Max.

However when I punch in the 300, 400, and 500 yard zero my drops almost exactly matchs the "calculated" ballistics of 3400 fps.

Now this is not theoretical drop. It is the actual drop that my rifle is shooting. And those are the actual amount of clicks that it takes to zero at 400 and 500 yards.

Can this be?? Can I be getting 3400 fps from a 75 A-Max in a 22-250. I know the actual facts sure support that. I wish my chrono wasn't broken. Tom.


Any load that even gets to or slightly above 3300 FPS on the Hodgens BC chart...and it only goes to 70 grains for that caliber....says the chamber pressure is at or above 63,000 PSI!....Hope ya carry good insurance..???
 
Sully I agree with you. But I am not getting any signs of pressure what so ever. And my load of H-414 is below max listed load. I just wonder how much more velociy I am picking up with the longer 28" barrel?? And I have heard the hand lapped Krieger barrels wil give up a little more velocity than most barrels??

It was not particularly hot or sunny on the days I was shooting.

All I know is that actual ballistics do not lie. And those ballistics are exactly what the rifle is doing?? Well I guess the Lord works in mysterious ways. Tom.
 
Tom, I changed the scope height variable to 2.0" in the calculations (as looking at your photo, it appears that your mounting rail and rings might put the scope a little higher than the standard 1.5"), all other factors being the same, and at 3200 fps, your POI with a 300 yard zero would be as follows:

100; +2.8"
200; +3.7"
300; 0
400; -9.1"

So knowing your scope height can be a somewhat critical factor, providing that your 'zero' is constant and specific at 300 yards.. 1/10 inch at 400 yards isn't that significant, but your PoI at 100 will be almost 1/2" lower...I would be hard pressed to develop a load that was so consistent as to keep a group within 1/10th inch at 400, but I might keep it within 1/2" at 100..

When I bump your velocity to 3400 fps, you lose your 9"drop at 400 yards...it shrinks to 7.2"..
 
Last edited:
Consider also that scopes have variation. Foe example having 1/4 moa clicks doesn't mean .2500000 MOA. It could be .24 or.26 and most of us would have no clue.

Great excersize though.
 
It'd be real helpful IF we had some chrony data.. Otherwise all we're doin is makin a a scientific wild a** guess.
 
Originally Posted By: zillaIt'd be real helpful IF we had some chrony data.. Otherwise all we're doin is makin a a scientific wild a** guess.



It would also be "real helpful" if you bothered to read the thread before you make a comment like that. Especially the part where I specifically said my chrono is broken?? But then why confuse the issue with the facts?? Sorry I did not meet your expectations. Tom.
 
Someone already mentioned the true click value, but u may also want to consider the drag function used to calculate the BC of that VLD bullet. Most ballistics programs use a G1 drag function, but some such as JBM can use different drag functions that more closely match the bullet types (VLD to VLD such as you have there). Check it on JBM and adjust the drag function for G7 and see what the velocity and drops come out.

Tom--u need to go to JBM and study those systems. It is a great resource for LR shooting and making (the most) accurate calcs. I couldn't null out the trjectory for my AR using a 65 JLK Low Drag for love or money and finally started adjusting the drag function until my data matched as closely as possible and i finally had it then.
 
Back
Top