Truing for BC - experience with accuracy of Barnes stated BC

[med358-boise]

Was just curious what other experiences might be, I am reasonably confident in the velocity of 2698 fps and the measured drops and the calculations are running a difference of 20% lower between stated and calculated BC.

It is possible, I was screwing things up but just curious of others experiences.

 

[Wachsmann]

So it's been my experience that when using a box velocity of store bought ammo you will need to get a velocity out of you own rifle. My 7mm-08 runs 20 fps slower than what's on the box generally. So I record my velocity's and I also check my rifle at distance usually I try for 800 to 1000 yards and then I see how the loads are flying to that distance and I may need to adjust velocity a little or true the velocity a little. But I try and get multiple shot over multiple outings so I know where my bullet will land. I do reload a lot and shoot a lot. I'm always tinkering with my loads and bullet combos. Sometimes a little too much. But short answer is you need to shoot you box ammo and get the velocity from your gun. I try not to adjust BC that much unless something just is not working out in my drop data. I shoot for about 1/4 minute of error inside 800yrds. With all the other factors 1/4 minute of error is hard to hold. In a perfect world we would use lasers and not have to worry about drop and wind.

 

[med358-boise]

I am not shooting factory ammo and am using a chronorgraph, not sure what in my post would have implied that. I am shooting handloads and chronographing with a Labradar; hence, the comment "I am reasonably confident in the velocity of 2698 fps."

I have validated drops on 4 or 5 different rifles. I normally don't worry about a difference in drop of 1-2 inches inside of 500 yards from expected. In this case, I was 4 1/2 low from expected at 400 yards and when I derived a BC from the actual drops, the calculated BC was over 20% below the stated BC.

 

[ARlife4me]

didn't state you weren't either, only about bc.

bc is measured at their altitude and atmospheric conditions (most likely) as that will change bc.

 

[Idaho Lefty]

Some Bullet Factories "Fudge" the BC Numbers, More than, others.
Sierra and Berger Bullets, ARE usually,.. "Close" to,.. "Spot On".
Hornady's New,. ELD-M's and ELD- X's, are also,.. very "Close" !
I won't Name,.. Who'se,. AREN'T !
Seeing 10-20 Percent difference in BC's can easily be SEEN, with some Bullets !

 

[ARlife4me]

Some Bullet Factories "Fudge" the BC Numbers, More than, others.
Sierra and Berger Bullets, ARE usually,.. "Close" to,.. "Spot On".
Hornady's New,. ELD-M's and ELD- X's, are also,.. very "Close" !
I won't Name,.. Who'se,. AREN'T !
Seeing 10-20 Percent difference in BC's can easily be SEEN, with some Bullets !

i will! NOSLER!

 

[slv hunter]

The difference can easily be 20% at your location. Adjust it and leave your velocity alone.

 

[Tiny Tim]

Are you certain its not in your turret. I have a scope that is spot on for drops at 1,2, & 300 yards, 1/2 MOA high at 400 yards and then back on till I hit that same spot on the next revolution.

I may have this reversed, but generally speaking, if drop error is consistent (say 1 moa) adjust BC (especially inside 500 yards). If drop error increases with distance, adjust MV. Someone correct this if I am wrong.

 

[med358-boise]

I wasn't dialing, I have fixed hash marks with known subtensions.