Range Report developing 308 ballistic tables for new rifle

[spotswood]

I would like some advice on what I may need to consider (variables and procedures) to develop my new ballistic tables for a new AIAW 308 with a 20 inch barrel with a S&B 5x25.
I do not handload. I have started shooting it with Black Hills 175 gr BTHP moly's.
I have a 200 yd zero and use my i phone with the JBM tactical ballistic program.
I am using a 1.8 sight elevation with standard atmospheric parameters with a 10 mph crosswind.
It is dead on at 200 and 300 yds same as the tables. When shooting at 800 yds I am 3 inches low when using the ballistic table data. I have found that adding 3 clicks (1/4 moa) brings me to dead on at 800 yds.
I think the scope is tracking well as with no crosswind and dialing in 102 clicks it is dead on at 800 yds and is giving me sub moa groups with no horizontal displacement. I am assuming that if it did not track properly that with 102 clicks dialed in it would be off horizontally if a no wind condition.
Why would my elevation adjustments be off? I have tried tables from the database using the black hills ammo and have used the projectile tables and used a variable BC along with 2600 fps. Both tables come up the same but are a little different from what I see shooting at the farther ranges.
Also, should I be considering switching to another bullet such as a AMAX from Hornady or a Scenar?
I have some other ammo from Fiocchi and Lapua that I plan to experiment with ranging from 155 gr Lapua scenars to fiocchi 165 and 168 grain BTHP.
Thanks

 

[deadly0311]

Re: developing 308 ballistic tables for new rifle

If you are 3 "clicks" low @ 800 and then you add 3 to your elevation that is your REAL WORLD Dope....most Ballistic programs have some inaccuracies, and are designed to get you "close" to first round hits in a new area. But shooting at each distance and recording that dope is the way to make up your range card. The JBM stuff only gets you close so you dont spend all day wasting ammo. The 175s and 155s are great choices, me personally i would stay away from all things 168

 

[RobertB]

Re: developing 308 ballistic tables for new rifle

I think shooting is the only true way to get a dead nuts chart. I like to have a good zero and get my conditions a right as I can. Once I have those and sice I don't have a crony I go shoot it (estimated Velocity) at say 600 and 1000yds at targets as small as I can shoot claybirds are good.Then I bounce my velocity around till the two distances match. You might have to play with bc as well. This is not the best way by any means but it works for what I need. Shot in a match a while back that I got 1st round hits out past a grand using this technique. A very experienced shooter taught me to do this and it works alot better for me than the times we ran it through a crony, put in the variables and and ran with it. We had about 3 MOA difference at a grand between the two.

 

[doc76251]

Re: developing 308 ballistic tables for new rifle

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: spotswood</div><div class="ubbcode-body">

I do not handload. <span style="color: #3366FF">First problem. You will have to change your dope every time you get a new lot of ammo.</span>

I am using a 1.8 sight elevation with standard atmospheric parameters with a 10 mph crosswind. <span style="color: #3366FF">Next problem: NOTHING is ever standard. Figure out your actual data an use it.</span>

It is dead on at 200 and 300 yds same as the tables. When shooting at 800 yds I am 3 inches low when using the ballistic table data. <span style="color: #3366FF">And this would be the result of using "standard data"</span>

I think the scope is tracking well as with no crosswind and dialing in 102 clicks it is dead on at 800 yds and is giving me sub moa groups with no horizontal displacement. I am assuming that if it did not track properly that with 102 clicks dialed in it would be off horizontally if a no wind condition. <span style="color: #3366FF">No if your scope wasn't tracking you would find yourself needing progressively more or less elevation adjustment than your table suggests.</span>

Why would my elevation adjustments be off? I have tried tables from the database using the black hills ammo and have used the projectile tables and used a variable BC along with 2600 fps. Both tables come up the same but are a little different from what I see shooting at the farther ranges. <span style="color: #3366FF">Crap in, crap out</span>

Thanks
</div></div>

Cheers,

Doc

 

[96C]

Re: developing 308 ballistic tables for new rifle

Like the lads said, get out there. Set up a solid steel target and start from the 100yd line, zero your rifle there. Move back 50 yd increments and ring the plate, RECORD that data. Windage isn't important at this stage you need to focus on Elevation in whatever increments your scope has been configured in.

STOP THINKING IN CLICKS! That's a surefire way to kick yourself in the nuts.

Open up excell in your computer, make a table:

YDS MOA
150 - 0.x 350 - x.x 550 - x.x 750 - x.x
200 - x.x 400 - x.x 600 - x.x 800 - x.x
250 - x.x 450 - x.x 650 - x.x 850 - x.x
300 - x.x 500 - x.x 700 - x.x 900 - x.x

Prit it out, laminate it, cut it to size and tape it to the side of your rifle. This will be your raw data. Not something a computer spat out using 10 variables that might be inaccurate. Bare in mind this data is accurate at that elevation, with that exact load in those weather conditions. But this will give you a base to work from.

Don't be too dependant on technology in this process, get out there and see it for yourself. Good luck mate

 

[vman]

Re: developing 308 ballistic tables for new rifle

Ive done something similar to what 96C has... works well

 

[northern shooter]

Re: developing 308 ballistic tables for new rifle

Do what the guys say just move it back every 25 to 50 yards and if the wind becomes a problem just use this formula FIRST DIGIT OF RANGE X WIND SPEED DIVIDED BY THE CONSTANT (here are the "CONSTANTS for the various ranged) 100-500 "15"
600 "14"
700-800 "13"
900 "12"
1000 "11"

heres an example taget at 700 yards wind speed of 10 mph full value wind. 7X10=70 divided by 13 = 5.38 rounded off to 5.5 MOA it may not be dead on the centre but youll be on target if you have half value wind divide your answer by 2 its all about trial and error shoot shoot shoot and then shoot after that shoot some more