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Why the change?

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Old 04-30-2003, 09:21 PM
Junior Member
Join Date: Apr 2003
Location: Santa Maria, CA
Posts: 21
Why the change?

My Savage 10FP-LE2 is currently sighted in at 1 1/2 " high at 100 yds. using 168 gr. Fed GM Match ammo. Today at the range, I tried the same ammo in 175 gr., and the point of impact shifted way right (at least 2"). I can understand a change in elevation, but I'm puzzled by the windage change. Any ideas appreciated. [img]images/icons/cool.gif[/img]
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Old 05-01-2003, 02:26 AM
Platinum Member
Join Date: Jun 2001
Location: Palmer, Alaska
Posts: 2,539
Re: Why the change?

If it isn't wind, it's most likely the barrel vibration difference as the bullet exits the muzzle that's causing it or maybe a scope mount issue has just popped up. It's been noted, using the "same" bullet, most of the barrels vibratation caused dispersion is vertical in nature and very, very little is horizontal. Using a different bullet, well, it's not too uncommon then.
Brent Moffitt
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Old 05-01-2003, 07:09 AM
Posts: n/a
Re: Why the change?

The heavier bullet and different velocity will cause different barrel harmonics.. I'm pretty sure.. also the recoil is different too. Is your barrel free floated? the different nharmonics may have caused the vibrations to contact somewhere...just a thought....
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Old 05-01-2003, 06:45 PM
Junior Member
Join Date: Apr 2003
Location: Reno, Nevada
Posts: 13
Re: Why the change?

Do you have any of that 168 Gr Match Ammo left? It would be interesting to see if it prints 2" right or if its still on zero. If the scope hasn't physically moved then I'd tend to agree with Brent & Wyo in the harmonics theory.

Harmonics obviously play a huge role in accuracy. I've seen groupings migrate upwards of an inch or so by simply verying the powder charge, so it would not total flabergast me if yours migrated by 2" from changing bullet weights.
Going to War without the French is like going hunting without your accordion
-- Gen. Norman Schwarzkof
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Old 05-02-2003, 06:40 PM
Junior Member
Join Date: Apr 2003
Location: Santa Maria, CA
Posts: 21
Re: Why the change?

Cobra: After experiencing the drift with the 175 gr., I shot 3 more groups using some more 168 gr. out of the same box, and they grouprd exactly as previous groups of 168 gr..

Side note: I used PMC 168 gr. Match rounds, and they group the same as the Fed. 168 gr. GM.

The barrel is free floated. So far the 175 gr. ammo is the only other weight I've tried. [img]images/icons/cool.gif[/img]
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Old 05-02-2003, 07:53 PM
Junior Member
Join Date: May 2003
Posts: 1
Re: Why the change?

I have shot a lot of rifles testing loads. I always load my ammo in 1/2 grain increments when working up loads. I have found that even with that little bit of powder diffence the point of impact changes significantly, not only up and down but to the left and right. It definantly has to do with the barrel vibration and the time when the bullet exits the barrel.
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Old 05-05-2003, 04:48 AM
Silver Member
Join Date: Apr 2003
Location: Newburgh NY
Posts: 235
Re: Why the change?

Hey Cobra by that quote do you think that Stormin' Norman is saying the French are LAME????
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