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Old April 28, 2013, 11:15 PM   #1
Metal god
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POI shift or what ?

Took the FCP-K out today . First three shots at 100 yards were one raged hole but to the left . OK no problem it was different ammo (Privi 168gr match) rather then the GMM I normally shoot . 1 MOA POI to the left was cus of different ammo , sure why not


Gun shooting well so I put a few 168gr GMM in and took 2 shots at 100 yards . Both touching each other all most dead center ( sorry forgot to take picture). Great , gun is perfect , I did nothing to the gun before shooting just loaded it and shot . I did clean the gun between outings . no copper solvents just some hoppes and a few brush strokes .

Cool gun is shooting exactly the way I left it so I start to reach out to the 300yd target with my GMM . I'm shooting at a 6" shoot-n-C. I dial my scope to what in my notes should be 300yds and take my first 3 shots , my spotter says miss and can't even see the POI . I see there is some wind but not much do to the angle . coming from behind us at 7 or 7:30 . I adjust and take 2 more shots and he says miss and still can't see the impact . He tells me to shoot some more and aim at a different target I say no I need to go see where these are hitting before I waist any more ammo . I go take a look and I'm about 3/4 to 1 MOA high


HMM does not sound right but I adjust the scope down 1 MOA 4 clicks and shot . Perfect right in the center . of the 6" target . I then move to one of the 3" targets and take 3 shots


Shot another group that was a 2" group

Why did my POI change so much at 300 yards but not at 100 yards from day one to day two . The temperature was quite a bit different but my ballistic calc says there should be almost no difference in POI from day one to day two . The ammo was from the same lot as the first day .

First day the out side temp was 67 degrees humidity was about 60 % and my ammo temp was 72 degrees

Today the out side temp was 83 degrees , humidity was 45% and my ammo was 81 degrees .

My calculator does not have a spot for ammo temp could that ten degree defference be the problem ?

Last edited by Metal god; April 29, 2013 at 01:02 AM.
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Old April 28, 2013, 11:31 PM   #2
big al hunter
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What power was the scope set at each day. POI can change significantly with power changes on some scopes. Most only vary a small amount. The temperature of the ammo can make a difference as well. Try the power settings next time, see how much yours changes.
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Old April 28, 2013, 11:50 PM   #3
Metal god
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Quote:
What power was the scope set at each day. POI can change significantly with power changes on some scopes.
Today it was on 12x and I think the same the first day . Although the first day was the first day ever for the rifle and scope . It was brand new so I was shooting it at times at different mags but I think most shots were at 12x and some at 14x . Nothing really over 14x or under 10x . All shots were using the center cross hairs and none of the substentions . I would hope if using the main center cross hairs I would not get any POI shifts .
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Old April 29, 2013, 12:21 AM   #4
big al hunter
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Have you checked the adjustments for repeatability. Set up a yard stick or tape measure across the room. And put the rifle in a stationary rest stable enough that adjusting the scope dial will not move the rifle. Make note of where the crosshair is and adjust up in 100 yard increments. Note the measurement at each setting. Bring it back down to zero again and check it back up the settings.
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Old April 29, 2013, 12:58 AM   #5
Metal god
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I have not done that but I did do the 6 shot scope tracking test .Zero rifle at 100 yards . Then shoot one shot in center of new target . Adjust 3 moa up and 3 moa right shoot while still aiming at center of target . adjust back to center then 3 moa left and 3 moa down . Do this to all 4 corners then take one last shot back at zero . It tracked perfect when I did that test the first day . I did not do that today . I will say this . The scope is not a high end scope . ( Vortex crossfire 2 , 6-18x44 ) I paid $200 for it and it could be the issue . I sure hope not cus my $60 tasco world class has less POI shift on my Ruger American . This crossfire will be put on my American when I get the scope I want for the FCP-K .

Thanks big al for giving me some ideas to think about .
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Old April 29, 2013, 08:46 AM   #6
Bart B.
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Shooting bullets and adjusting their impact to check a scope's adjustments allows errors equal to the accuracy of the rifle and ammo plus the non repeatability of the shooter. A 1 MOA or more error's normal.

If you scope's got 1/4 MOA/inch clicks, you and your stuff has to shoot no worse than 1/10th MOA using the "boxing" method to see if they really are that accurate. You don't measure how thick a human hair is with a yardstick, do you?

Do as Big Al suggests. That's gonna get much more accurate results.
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Last edited by Bart B.; April 29, 2013 at 09:54 AM.
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Old April 29, 2013, 11:41 AM   #7
Metal god
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yea the more I think about it the more I think it's the scope

Quote:
Make note of where the crosshair is and adjust up in 100 yard increments
I'll do the other test . What does adjust up in 100 yard increments mean and or what would the click value be on a 1/4 moa per click scoipe .is there a min distance the yard stick should be away from the rifle . I'm sure it's simple but im drawing a blank on all this .
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Old April 29, 2013, 02:48 PM   #8
Bart B.
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Your 1/4 MOA clicks are within a couple percent of 1/4 inch per hundred yards.

Set the yardstick up at 50 yards. 40 clicks (that's 10 MOA or inches at 100 yards) should move the reticule 5 inches on the yardstick.
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Old April 29, 2013, 03:32 PM   #9
Metal god
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OK sounds more like what I was thinking . but when big al said
Quote:
Set up a yard stick or tape measure across the room.
That sounds like I can do it in my livingroom at 20 feet or so . Is it better to do it at a longer distance or shorter .
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Old April 29, 2013, 04:08 PM   #10
Bart B.
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Shortest distance your scope will focus at will work good enough. Just remember that if the distance is 33.33 yards, one 1/4 MOA/inch click will move 1/12th inch on the scale. The range is one third of 100 yards and 1/3 of 1/4 is 1/12th.

In other words, don't forget to use grade school math.
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Old April 29, 2013, 11:49 PM   #11
big al hunter
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Quote:
What does adjust up in 100 yard increments mean
Sorry, I wasn't very clear on that one. It made sense in my head, not on paper.

What I meant was: adjust your scope up in MOA for your load as if you were shooting a target every hundred yards. So up whatever your load needs at 200, 300, 400 yards. Then back down to zero, checking the measurements both directions. Then repeat.

ETA Bart is correct the farther away the measuring tape is the more accurate the test. Across the room might be difficult to see small errors. Maybe across the yard.
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