Changing bcs to match velocity

[david g ranes]

I just trued up my Silhouette Match rifle. I had chronographed MV and the bullet BC and was trying to adjust them to match my drops. I worked out the dial ups that worked for the 4 silhouette yardages plus one dial up required for 500 yards. I could never quite jigger MV and BC in my app to match what was working. I just started over and used the 547 yards, the chronographed MV, the listed BC and put in the dial up required and had my Strelok Pro adjusted the value per click. The Strelok app came up with .228 moa per click and when I tested it against the dial ups that worked the new moa value per click was dead on for 5 different yardages. Maybe you need to true up your scope click values?

Don't know if I can or how on the geoballistics app I checked my scope earlier and it was moving the expected amount I was dialing at 200 yds. David

 

[COBrad]

Have you tried a tall target test to see what the moa or mil movement actually is? I have an old scope that always returns to zero and gives precise and repeatable adjustments, but it's 13% short of the actual moa solutions my ballistic app gives. Once I get out towards 500 yards shooting at prairie dogs I multiply by 1.13 then dial that number in and I'm right on.

 

[AggieHunter]

I would suggest to go to Darrell Holland's website Holland Gunsmithing and look at his calculator. Last fall I had a 7wsm that I wanted to zero w/180 grain bullet. I perfectly zeroed my rifle at 0" at 100 yards and put that data in the calculator. Then not touching the scope, I shot a 3 shot group at 500 yards & measured the drop. I went back to his calculator put the inch drop into the calculator and it spit out my trued BC on the bullet I was shooting. Then I adjusted my drop on my rifle scope and shot another 3 shot w/the adjusted data. My group was a 2.5" triangle at 500 yards - figure that MOA. I am a true believer in his system. Or call him if you chose.

 

[73driver]

Don't know if I can or how on the geoballistics app I checked my scope earlier and it was moving the expected amount I was dialing at 200 yds. David

200 yards might not be far enough for a click value issue to show up. Do you have a measured MV? BC's should be a good known value and yards can be measured with fair accuracy using a laser range finder and a tall test should give verify what your scope is doing and of course scope height above bore is important. The more variables you can accurately measure/verify the better chance of getting your ballistic solver trued up.

 

[Flintlock shooter]

If you have a good chrono (MS/LR) then your MV should be accurate. Verify that my shooting a small target at 400-450 yards. I use a 5" circle. MV will give you fairly good accuracy out to around 650 yards. After you verify MV shoot at a longer range target. Ideally that will be within 10% of the distance where your bullet goes transonic. If the impact is low, lower the BC. If impact is high, raise BC. Once your impacts are on the water line, you should be just fine.
Personally I true my BC at about 1100 yards for my match rifle because there are normally only a target or two past that. For my ELR gun, I true BC at closer to 1700 yards.

 

[david g ranes]

This is 2 shots at 695 yards I know my gun I know my velocity numbers just don't match trying to figure out why don't have trouble pulling a trigger my math just doesn't match. David. The target on the right is my third shot different target high shot was first out of gun to start getting my data. David