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Ballistic gurus please help, thanks #5363742 10/16/14 05:48 PM
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I shoot a Sako Finnlight 30-06 with a Leuopold Vari X III 3.5x10 40mm scope mounted to it. I have owned this rifle for 10+ years. I absolutely love it. It is dead nails at distances I have taken it to shooting reliable groups at 100 and 200 yards. I haven't shot farther because for 1) I have no need to and 2) my bullet drop is significant and is the reason I am writing this.

I use Barnes Vortex 180 grain for big game (i.e. elk). I have my scope dialed in to be zero at 100yds. It is dead on. When I take it to two hundred yards, it is still dead on shooting groups sub 1 inch however the bullet drop is consistently 10.5 inches low. To me, this seems greatly excessive. I know Barnes states the bullet drop should be around 2.0 inches on their box which I assume is a gross average and would expect a 1-1.5 +/- deviation from that, but 10.5 inches? What, if anything could be causing this? Or is that just how it shoots and I should continue to just "holdover" 10.5inches like I have been?

Re: Ballistic gurus please help, thanks [Re: Theringworm] #5363770 10/16/14 06:08 PM
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Bullet drop is really a simple deal. Believe the bullet. If your 180 grain Barnes TTSX (blue tip) with a .484 G1 BC is running close to the 2800 fps, then your drop should be 3.61" at 200 yards from a dead on 100 yard zero. To get the 10.5" of drop at 200 yards, I come up with a muzzle speed of 1850 fps. So, somethings not adding up. It always helps to chronograph your loads to know how fast they are going to calculate your drop and wind drift. But, I can not come up with why there is 10.5" of drop from a 100 yard zero, if it is truly zero'd at 100 yards. Did you confirm the 100 yard zero "with this ammo and bullet" before you shot to 200 yards? If you are zero'd with some other ammo, and just went to 200 yards with this ammo, that's probably why.



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Re: Ballistic gurus please help, thanks [Re: ChadTRG42] #5363783 10/16/14 06:15 PM
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I literally just got back from the range this morning. Leaving for an elk trip tomorrow and just wanted to make sure all is well. I put three shots down range at 100yds. All three dead bulls eye. Without making any scope adjustments I went to 200yds to verify exactly where my bullet drop would be. I fired a total of 7 shots at 200 yds, once again, not having made any scope elevation adjustments. All 7 shots were 10-11 inches low, but in the middle of the target. All bullets were from the same lot and even the same box. I am by no means an expert with ballistics. I have hunted all my life and enjoy shooting. I am just now trying to pick up/learn something about ballistics, etc. I don't have a chronograph nor do I reload (though some day that is a desire of mine). I will say that I have never truly compared the bullet drop from 100 to 200 yds in this rifle ever before so I am not saying this is a new issue. I was a teenager when I got this rifle and didn't understand anything about shooting back then. Now that I have time and am trying to become a better marksman I am taking more notice and am trying to apply what tidbits I have learned throughout the past several years to make me better. I clearly know I have a long ways to go but I have to start somewhere. I appreciate your time.

Last edited by Theringworm; 10/16/14 06:24 PM.
Re: Ballistic gurus please help, thanks [Re: Theringworm] #5363890 10/16/14 07:16 PM
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Doesnt add up to me either. Should drop .5 Mil at 200 yards which is 3.6" on the paper. And that cartridge should be making well above 1850 fps, unless its wearing a 16" barrel which I highly doubt.


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Re: Ballistic gurus please help, thanks [Re: Theringworm] #5363930 10/16/14 07:34 PM
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If that's the case, I have no idea why it's 10-11" low at 200, unless it's a scope parallax issue or slow bullet speed.



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Re: Ballistic gurus please help, thanks [Re: Theringworm] #5363981 10/16/14 08:12 PM
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random question here... Could the rounds have gotten wet? like only part of the charge going off?


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Re: Ballistic gurus please help, thanks [Re: catslayer] #5364057 10/16/14 08:59 PM
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He says sub 1" groups at 200 yards. Wet ammo won't do that.


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Re: Ballistic gurus please help, thanks [Re: FiremanJG] #5364070 10/16/14 09:05 PM
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Originally Posted By: FiremanJG
He says sub 1" groups at 200 yards. Wet ammo won't do that.


true, wouldn't be consistent...


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Re: Ballistic gurus please help, thanks [Re: Theringworm] #5364127 10/16/14 09:37 PM
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The ammo by my knowledge has never been wet. It is a year old but other than being in my backpack while hunting last year it has never been wet. I live in West TX so low humidity and my gun safe has more dehumidifying rods/bags/crap than it needs. I do recall about a year ago shooting at 200yds and it was hitting around 4-5 inches low which would go along with what you guys are saying. I don't know if I adjusted the scope though back then. I did fail to mention I was not shooting off a gun rest but just laid on top of a shooting bean bag. I am young and don't have any tremors so it couldn't be off that much because of me, but then again maybe it is me. 100yds groups sub 1 in. 200 yds, were not not sub 1in, but all 7 shots were around 3 inch groups max. I guess after I get back I'll put it on my sled and see if it makes a difference. I'll keep you posted. Appreciate your help though.

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