Determining true BC

[Forester]

I have been shooting with good results the Hornady 110gr V-Max through my Savage 12FV this spring and have taken a few groundhogs with it so far. I wanted to work out a real drop chart and get an idea of what kind of groups I might expect beyond the 200 yards I have been working at so far so I took advantage of a nice calm morning today...can some of you that are more experienced at this tell me if my logic is valid here?

I first made sure I had the rifle well zeroed at 200yards. I checked my 200 yard groups through the Chrono and got the expected 3145fps with very low ES(5-10).

I then moved out to 400 and used a free ballistics program to get close on how much to come up on the scope. After shooting a 3 shot group I adjusted the scope to zero at 400. I shot a group to confirm and had a good zero at 400 yards.

I used the actual come up to adjust the BC of the bullet in the program until the programs numbers matched my own.

I then moved back to 500 and used my new BC in the program to bring the scope up. Hits were exactly at the correct elevation on target.

Heres what I found hard to believe, if I did things right, my actual BC is .286 instead of the .177 claimed by Hornady. it seems hard to believe that my real BC could be 60% higher than what is claimed by Hornady.

By the way, groups:

200= .41MOA
400= .44MOA
500= .38MOA

Groups at 200 are round, at 4 and 500 most of the dispersion is windage, very little elevation.

Darn good for a (relatively) cheap rifle and Bushnell scope! All I have done is bed the action in the factory stock and open the barrel channel up to make sure it can not touch.

Thanks for checking my method!

[jwp475]

What is your elevation? did you correct the BC for elevation?

[Forester]

Originally Posted by jwp475

What is your elevation? did you correct the BC for elevation?

I used 1000 for all calculations...the areas I hunt will run from about 800 to 2500 feet. Mostly closer to 1000-1500

Not using the exact elevation that I was shooting would mean I have included some of the elevation effect in my real world BC instead of letting the program do things the right way correct?

If I am figuring things right and the worst case scenario puts me 1000 feet higher in elevation I will be .3 MOA off at 500 yards...for the use this particular load will get I can live with that.

[jwp475]

Bullet companies BC's are corrected to sea level and the ballistics programs take this into account if memory serves, so if your BC is at altitude then it will have a higher number than one that is corrected to sea level.

[royinidaho]

Forester,

Quit worrying about it and go shoot stuff.

When you have things tuned that close you become one of the few to be envied.

When I input the .7xx for a Sierra 300 gr SMK and input the info for 4500 feet and other conditions the software jumps it to something like .85.

I don't understand it but the drop chart works.

[Forester]

Originally Posted by royinidaho

Forester,

Quit worrying about it and go shoot stuff.

When you have things tuned that close you become one of the few to be envied.

When I input the .7xx for a Sierra 300 gr SMK and input the info for 4500 feet and other conditions the software jumps it to something like .85.

I don't understand it but the drop chart works.

See I have this sickness...I blame my father for it. If there is a higher level of perfection to be attained I can't resist trying for it.

I don't think many here would envy my shooting...500 yards still seems like a D@%& long ways away to me

[Waltech Jim]

Originally Posted by Forester

Heres what I found hard to believe, if I did things right, my actual BC is .286 instead of the .177 claimed by Hornady. it seems hard to believe that my real BC could be 60% higher than what is claimed by Hornady.

Forester,

How happy would you be if Hornady had a BC of .290 for their 308 cal, 110 V-max. (I assume that is the bullet you are talking about.)?

They obviously just changed it to match your results. Good job.

Jim