168 gr. 308

tommyc279

Well-Known Member
Joined
Dec 30, 2007
Messages
146
Location
Haslett Michigan
I have been shooting the american eagle 168grl. OTM and have had amazing groups. The only problems I have been having are my ballistic charts are not working with the real groups. what I am looking for is he bc of this slug and any real data that anyone has on shooting this round. At 200 yards they are perfect and 300 yards they are 2.7 inches low after the adjustments are made. I cant figure out the why this is happening
 

bowhunthard

Well-Known Member
Joined
Sep 5, 2008
Messages
1,030
Location
Northeast PA
First of all, does the box give the velocity and bullet b.c.? Or at least the velocity? What is your barrel length, because this can affect velocity by as much as -/+ 50 fps per inch of barrel length. You'll need an actual velocity for your barrel, before you can actually dial your scope, and the only way to get this data is to chronograph it. The other way is to shoot each yardage and write down the number of clicks it took to dial in.

American eagle is a cheap brand made by Federal, so they could possibly be using the 168 gr SMK (b.c. = 0.447 @ 2600-2100fps) or maybe the 168 Speer (b.c. = 0.480).

The b.c. could also figured out by chronographing @ 2 different yardages or shooting @ 2 different yardages and calculating the drop formula.

If you know the bc and the velocity, I'd be more than happy to make a ballistic chart for you, as I have the SierraI6 software.

Good Luck.
 
Last edited:

trebark

Well-Known Member
Joined
Jan 16, 2008
Messages
3,541
Location
Falls Church, VA
I have been shooting the american eagle 168grl. OTM and have had amazing groups. The only problems I have been having are my ballistic charts are not working with the real groups. what I am looking for is he bc of this slug and any real data that anyone has on shooting this round. At 200 yards they are perfect and 300 yards they are 2.7 inches low after the adjustments are made. I cant figure out the why this is happening

The trouble you're running into here is the difference between what the 'book' says and reality. What you need to do is some trajectory validation.

Zero your rifle at 100 yards. Then whatever you 'book' says to adjust for 200 yards, make that scope adjustment and shoot a 200 yard group. Then make the 300 yard adjustment according to your 'book' and shoot a group, then 400, 600 and so on. Then go out and measure the difference between the 'book' and the reality. You can now calculate your trajectory and have accurate adjustments for your various distances.

Of course, once you have this validated trajectory, you will have to go out again and check it...just to be sure.
 

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