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Strange thing happening with at range?

 
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  #1  
Old 06-23-2008, 12:32 AM
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Strange thing happening with at range?

I just started trying some berger 80gr VLD's in my 223 the load is 25.1gr of varget bullet seated on the lands shot 1.12" at 100 shot 1.1" at 200 and 1.125" at 300, Anyone ever seen this before, Any reason for this?
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  #2  
Old 06-23-2008, 08:19 AM
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THis is relatively common with heavy for caliber VLD bullets. You are seeing the bullet go to sleep if you will as range increases. This means the bullet is fighting off the rotational effects of the rifling withing the first 100 yards or so of being fired.

The rifling makes the bullet spin around the axial center of the bore which often times is not the same as the bullets center of gravity as such, when the bullet is released by the rifling, the bullet is trying to transition from rotating around the axial center of the bore to rotating around the center of gravity of the bullet. This causes a wobble, if you will until the bullet "goes to sleep" and spins true around its center of gravity.

This is why the groups are larger as far as MOA measurement at closer range then you see it at longer range, just as you are seeing.

The longer the bullet the more you see this and often at longer ranges. The faster the bullet is rotated, again, on average the farther you will see this.

You often see this if rotation is marginal.

Again, there are many, MANY very good loads that are passed up on because many feel that if its not a 1/2 moa load at 100 yards, there is no need for any testing at long range. With conventional bullets, that may have some merit but with a heavy for caliber VLD type bullet that is often not the case at all.

So if your getting good, consistantly shaped groups and your velocity spreads are tight, your much wiser to test at long range and often times a much better result will show up then expected.

It could also be a result of paralax adjustment. If your PA is adjusted well for 300 yards but not at 100 yards, your groups will be larger if your eye position is not consistant at the closer ranges. You see this with non PA scopes or lower quality scopes or scopes that the shooter does not adjust PA prior to shooting groups.
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Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
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  #3  
Old 06-23-2008, 09:39 AM
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I was wondering if that was what was happening (bullet going to sleep) I will try it at 400+ and post back. Scope does have P.A. Thanks for your help, This is my first barrel that was built for the big heavies. Any other advice would be greatly appreciated?
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  #4  
Old 06-23-2008, 10:31 AM
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Your right near 1/3 moa at 300 yards, hard to complain about that. Only other thing I would check would be your velocities, at closer ranges, your velocity extreme spreads will not make alot of difference, at longer ranges, you will see some significant vertical stringing if you have a high extreme Spread in your ammo. I generally look to get as low as possible in extreme velocity spread but again, if you can get under 20 fps for a 10 shot string, great, into the teens, even better and single digits, rare but possible with some rifles. sub 20 fps will serve you well for the effective range of your combination.

DO not get to hung up on searching for those magical single digit extreme spreads, get her under 20 fps and get out and practice.

Do not fall into a case of "tinkeritis". This can be a serious condition for the long range shooter, better to find a good consistant, accurate load and then get out and practice in the field then tinker with things looking for that magical load that may or may not be possible with your rifle.
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Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
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  #5  
Old 06-23-2008, 12:11 PM
Lightvarmint
 
Posts: n/a
Check the mirage shade on your barrel and ensure the barrel heat is not getting into the line of sight of the scope. We shoot at first light in the mornings to minimize ground mirage. Sometimes we get in a hurry and forget to put the mirage shade on the barrel and you can really see it on the target when the barrel warms up. We then install said mirage shade and we are back to good times and small groups.

It is just so easy to take care of this accuracy-robbing condition. However, it may not apply to you.

James
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  #6  
Old 06-23-2008, 12:16 PM
Lightvarmint
 
Posts: n/a
Quote:
Originally Posted by Fiftydriver View Post
THis is relatively common with heavy for caliber VLD bullets. You are seeing the bullet go to sleep if you will as range increases. This means the bullet is fighting off the rotational effects of the rifling withing the first 100 yards or so of being fired.

The rifling makes the bullet spin around the axial center of the bore which often times is not the same as the bullets center of gravity as such, when the bullet is released by the rifling, the bullet is trying to transition from rotating around the axial center of the bore to rotating around the center of gravity of the bullet. This causes a wobble, if you will until the bullet "goes to sleep" and spins true around its center of gravity.

This is why the groups are larger as far as MOA measurement at closer range then you see it at longer range, just as you are seeing.

The longer the bullet the more you see this and often at longer ranges. The faster the bullet is rotated, again, on average the farther you will see this.

You often see this if rotation is marginal.

Again, there are many, MANY very good loads that are passed up on because many feel that if its not a 1/2 moa load at 100 yards, there is no need for any testing at long range. With conventional bullets, that may have some merit but with a heavy for caliber VLD type bullet that is often not the case at all.

So if your getting good, consistantly shaped groups and your velocity spreads are tight, your much wiser to test at long range and often times a much better result will show up then expected.

It could also be a result of paralax adjustment. If your PA is adjusted well for 300 yards but not at 100 yards, your groups will be larger if your eye position is not consistant at the closer ranges. You see this with non PA scopes or lower quality scopes or scopes that the shooter does not adjust PA prior to shooting groups.
Kirby,

When you get your 220 grain bullets from Georgia for testing, do me a favor and see if you get the same phenomenon with them as the ones you have been using. We are not seeing what you are describing down here at 92 feet above sea level. Maybe it is an altitude issue? Anyway, your findings will be interesting.

Good shooting,

James
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  #7  
Old 06-27-2008, 06:55 PM
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Join Date: Mar 2004
Posts: 150
Hey guys I talked to Eric Steckler at berger bullets (excellent company and excellent customer service) and he said I should try seating the bullets 20 or 30 thousands off the lands. I had been seating on the lands and 10 thousands jam as I had thought that was the right thing to do. Mr. Steckler informed me that the vld's do not have to be seated that way. To make a long story short I tried 5 different loads an all of them shot under 1/2 inch. I do want to thank Fiftydriver for trying to help on this issue. I know it's hard to troubleshoot something without being there.
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