Pre-mil 308 shoots a nice group @ 125 yards (top group).

At 200 yards it turns to crap (bottom group).

Loads are 150 grn. ballistic tips running at 2810 fps. ballistics shows a 2" drop @200 but I'm getting quite a bit more. Any ideas?



BP...

When that big buck comes by at 200 yds, aim a foot back and 6" high.

Bring it up 6 clicks and left 2 clicks. That should put you minute of deer out to about 300.

No problem.

Scope mounts not parallel to bore. Tough nut to crack!

windy? Have you chrono'ed the speed? Any elevation difference in your targets?

So about 0.75" high at 125 yards, and 6" low at 200?

That right there says it can't be doing 2810fps.. when sighted in that way at 125 yards, it should be less than 2" low at 200.

Eliminate the far left shot as a flyer, and the far right shot as a flyer, and your move to the right isn't quite so extreme.

But the drop doesn't make sense.

Chrono in error would be my guess? Brass and primers look lo pressure? My .308 99 F first loads under 1" so I quit there.
Copied and pasted .308 Win Trajectory
http://i141.photobucket.com/albums/...ts/BulletPath3different308bullets250.jpg

Light winds going from left to right across target.

Chrono'ed loads at this session with an average of 2808fps with a spread of 7fps. Verified chronograph with a 223 and a 22LR. Everything OK.

Slightly more downhill shoot on the 200 yrd. target.

Loads are 47.g Varget, F/C case, Win. primer, 150 Nosler Ballistic Tip

BP...

Shooting down hill may well be the problem. When shooting at either an up or down angle to hit point of aim you've got to aim high. Shooting up or down causes you to hit low. The greater the angle the greater the deviation from your point of aim. The wind is not your friend either. Even a light wind can wreak havoc on the strike of your bullet and group size.

right on about the wind, the extra 100yds might make a big difference, stake out some wind flags

I believe you have this backward.

I was taught that shooting up or down hill would result in the point of impact being high. Are the cross hairs tilted? That much drop at 200 yards is a puzzler if your velocity is true.

Crosshairs ok.
Velosity I'm sure is true.
The downhill elevation diference is probably between 3 and 5 feet over 200 yards.
I had a smith tell me a few years back that a barrel he had bore scoped had some pitting and would never be more than a 150 yard rifle. Maybe I need to get mine scoped.

BP...

BP, Just a thought , but have you tried a shorter bullet with that rifle. Nosler BT 150 gr are long bullets, perhaps they're not stabilized past 100 yrds as the velocity drops off. I've seen this with a couple times with loads that shot good at 100 but went to crap at 300. Here's a link to bullet data base that shows the length of different bullets, you can see that Bal Tip is even longer than Hornady 180 gr BTSP

http://www.shootforum.com/forum/bulletdb.html
Once again it's just a thought. Good luck

Lee

Good thinking. I'll have to experiment.

BP...

3-5 ft. drop in elevation wouldn't make any difference.

You could be right. I was a bit addled by liquor at the time and have had another four fingers just earlier so I won't be able to check for errors until much later in the morning. Well, maybe early afternoon. Anyway, bottom line is that shooting up or down hill needs a correction. When zeroing and checking for longer range drop you need to do it on as dead flat level ground as possible. Altitude will also screw you up. The only way to really know where your rifle hits at extended ranges is to find a 1000 yard range and shoot lots of stuff at different distances downrange and see where it hits. Even the computer generated tables are wrong for the most part as they don't take into account real world conditions. The only way to really know is to do a lot of shooting in perfect conditions.

Problem is clear. Target backer was made in China.

Too Funny!