long range shooting

[sambo]

got a quick question about shooting at different long range targets, do you all use a ballastic software to calculate the bullet drop at various distances and how would you go about using it in the field? like do you write it down on a paper and stick to the side of the stock or what? i see most long range scopes are calloberated for 100 yard increments, what if your target is at 532 yards, how do you compensate for the 32 yards? i hope my question is clear

thanks in advance
sambo

 

[Boyd Heaton]

Sambo,the ballistic program I use is the JBM program.And I run it in 50 yard inc's.

I start this one at 550 yard's.The differance between 550 and 600 yard's is about 1 MOA...So 500 to 532 yard's would be around .5 Moa.I shoot my gun's enough that a difference of 25 or 30 yard's is a add or take off a few click's to be where I need..Hope this helped some.....

[ 01-13-2003: Message edited by: Boyd Heaton ]

 

[ewallace]

I use a drop chart try this site http://internet.cybermesa.com/~jbm/ballistics/traj/traj.html make a chart from JBM and print it out so you can take it in the field. I would round the 532 yards to 520 or 540. I make my chart in 20 yard increments.
Crow Mag

 

[sambo]

Thanks guys for the info, that's excactly what i'm looking for. i like that site a lot. is the sight height around 1.5 in most cases? or is it more for the 50 objective lense scope?
sambo

[ 01-13-2003: Message edited by: sambo ]

 

[Michael Eichele]

Sambo,

I print sheets of ballistics that have been calculated in 1000 feet ASL increments and 10 degree F conditions. For example: If I know I am going to be hunting between 3000 and 6000 feet at 30-70 degrees I print ballistics in 25 yard increments at 3000' at 30,40,50,60,70 degrees. Then 4000 feet at 30,40,50,60,70 degrees and so on. I pack them up in a ziplock bag and I am good to go. There is also 10MPH wind in there as well. Then I print on the back of those ballistics the raw or real bullet drops (drops figured with the gun fired level with the earth.) with a seperate sheet of multipliers for angle shooting.

 

[Guest]

[ 07-11-2003: Message edited by: S1 ]

 

[Brent]

S1, I agree completely.
The real world data you start to develope will help you fill in the blanks. If you have test data at 500 and 600 yards and trajectory is following a program you have close at these distances 532yds will be pretty easy to figure, say for instance the 500yd is 7.7moa and 600yd is 10.4moa and your following this real close. Now you go to the program and it says 520yds is 8.3moa and 540yds is 8.8moa, now there isn't much guesswork to find 532yd data. I would go with 8.5moa for a basis.

 

[Ian M]

S1,
Borrowing one of your terms, my "real world" hunting distance is out to 650-700 yards with my .308 rifles. Even at this more modest long range I have found that I am best served by shooting drops and using actual field measurements. I have large 2'x4' sheets of 1/2" steel plate that we paint white and can see bullet impacts very well on.
Your point about relative air density factors is a very valid one, we hunted 1500 feet above where we did all our zeros and one rifle's point of impact moved up 1.5 minutes. Resulted in a clean miss at 505 when he tried to spine a buck - hit about 7" higher than anticipated.
We had our data but blew it on that one, lesson learned. Re-zeroed and he broke a spine at 530 on a mulie buck.

 

[Guest]

[ 07-11-2003: Message edited by: S1 ]

 

[Brent]

S1,

I've done the same before, with only one sheet standing vertical using the 308's.
The "actual" drop is now measurable! If you take velocity readings the "actual" BC is now on the money too! The tracking problems will be elliminated like you said.

An easy way to get the "actual" BC of a bullet your working with, which helps.

 

[Ian M]

S1,
My partner and I did the exact same thing a while back, only our target stand was 12 1/2 feet tall by 3 feet wide and we shot in 100 yard increments from 100 to 700. Had to pile boulders on the base because of the wind, thing was pretty top-heavy but it sure worked well. Gave us very nice actual drop figures for the two rifles and loads before a hunt.

If we stay with a 100 yard zero we can catch our groups on the 12.5 foot stand out to 700 with most loads. Past 700 we use our big steel plates - 2'x4' is nice because we usually get more windage variations.

 

[bgordon]

I do the reverse of that to verify bullet BC.
Find a calm day and get the rifle zeroed in at 600 yards (for instance). Being off a bit doesn't cause problems, just make sure your group is low enough that the 100 yard group will still be on paper. Then, just go in to 100 yards and take a couple of shots, making sure to use the same aiming point as further out. Do NOT change your scope windage or elevation adjustments. Measure the actual VERTICAL distance from center to center of the two groups and that gives you the actual amount of moa to get from 100 to the longer distance. Don't measure the center to center distance, measure the vertical difference between the group centers. If you have also chronographed those particular shots you have the necessary information to determine the actual average BC for that distance. Plug the info into the software and out pops an extremely accurate chart to give come-ups for intermediate distances.
Then all you have to do is verify the information at a few distances. At least for 1000 yards and closer, this has worked superbly for me.
This past weekend the projected 1000 yard scope setting was within 1/2 moa of the actual settings. First sighter was a 9 at 8 oclock with a new load. If I had gotten the windage correct it would have given me an X.

This method is also good to verify if you have enough vertical adjustment to get to whatever maximum yardage you intend to shoot. Have a tall piece of paper at 100 yards and put an aiming dot in the very bottom. Do one shot to verify 100 yard zero, then adjust the scope vertical 5 moa at a time. Take a shot each 5 moa. When the scope runs out of vertical take a shot and measure the vertical distance between the top and bottom holes and you will have the maximum vertical adjustment the rifle will do with the setup. Quite often the scope adjustment will turn further than the crosshairs will actually adjust for, which is the reason for a shot every 5 moa. That way you can know when the scope actually runs out of adjustment. I had a cheap tasco scope one time that would turn several full turns past the last actual adjustment and caused me problems because I expected it would get to 1000, but in actuality it would only get to 550.

[ 01-15-2003: Message edited by: Bruce Gordon ]

 

[Brent]

Bruce, I have a Leopold that the last 5moa is useless too...
I like the top of the plywood as a target, it makes a very clear line to hold from and the drop down from there is much more pronounced than the 600 yd zero gives because the bullets are impacting on the target on their way upto the max ordinate and on their way down too, easy to mix up groups and their closer together as well.

The 600 yrd group works out close to the bottom on a sheet of plywood depending on the cartridge used and groups are decending and easily kept track of too. I start by covering a sheet with two rows of frezer paper taped together, front and back, and stapled to the sheet. My 100yd zero is already established so I go to 200, 300, 400, 500 and 600, as fast as I can move and get setup again firing 3-5rds at each distance. Seeing the bullet holes in the freezer paper makes it much easier to plot velocities for each shot on a tablets target with relation to each round fired if you do this. Measure the groups center to center and you have it.

Do this at various temps, BP (and angles if an option) and you can develope super accrate drop charts and verify the accuracy of your programs modification of various temp, BP and angles too. If you use a crony doing it you'll have accurate velocities to input at the different temps as well, which will help you enormously.