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Old April 25, 2009, 08:15 PM   #1
PCJim
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Join Date: July 11, 2008
Location: FL
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Frustration with a new scope

I mounted a new, Weaver 2.5-10x56 30mm scope on my .243 bolt rifle this week using Zee Signature high mount rings. Went to the range today with 15 rounds for sighting in, with the intent to test some new rounds in the rifle thereafter. Using a front rest and rear bag with the target at 50 yards, the first shot was 1/4" directly above the + in the center of the target. GREAT!! Next safe line, I moved the target to 100 yards. First shot was about 4" high at 12 o'clock (oc). Not too bad, but it should have been closer. Looking for a grouping to adjust the scope, the second shot was worse, out about 8" at 2 oc. What gives here? Third shot was out maybe 9" at 1:30 oc and the fourth and fifth shots went totally off the paper to the right. What the heck is going on? These are bench shots, which I could hold within an inch with the old scope. And I had yet to make the first adjustment to the scope!

In total frustration, I rechecked all the screws. They were all OK, pretty tight, although I did "tweek" them a bit more (I have a bad habit of over torqueing screws/bolts/nuts). I went back to trying to figure where the POI was. Holding POA at the left edge of the target, POI was 3" to right of the X. I ended up having to adjust the scope some 14+" to the left to try to zero in on the target. I used up all 15 of the sighting in rounds plus the first 5 of the ones I wanted to begin testing for accuracy.

Has anyone encountered such erratic behavior from a quality scope, especially after the first round at 50 yards was so dead on?
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Old April 26, 2009, 11:54 AM   #2
Unclenick
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Sounds like the scope and/or rings were settling. It should not be that far off, as you say. I would loosen the rings and roll the scope back and forth to see if the croshairs stay on target or not? Or better still, make a scope roller jig with wood and nylon round-head screws (image below). You adjust the settings until the crosshairs don't move when you roll the scope around on the support. That centers them. At that point if your rings are centered and parallel to the bore, when you mount the scope, the 100 yard target should be impacted low by the amount the scope axis is above the bore plus the bullet drop. Even with a 100 grain bullet at 2800 fps, that drop is only about 2.3 inches. If your scope axis is 1.5" above the bore axis, then this is a total of 3.8 inches low.

I would just try grouping it like that with no further adjustment. If the shots move around after that, then you have something loose. Unfortunately that something could be inside the scope, which would necessitate a warranty return. Pulling the scope back off and rotating it in the jig again should tell you if its adjustments have slipped? Alternately, if you have a laser bore sighter you should be able to see the laser spot shift relative to the crosshairs if the scope is shifting?

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Old April 26, 2009, 12:16 PM   #3
PCJim
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Unclenick, thanks for the confidence boost. Since I've had 20 hours now to churn the thought process, I agree that it could have been settling, but what a frustrating disappointment.

I really like the design concept of the Zee Signature rings, with the nylon bushing to self center the scope and prevent surface marring. I have heard that the bushings concept was used many years ago by other manufacturers but that it did not sell well. Personally, I think it is a great idea (guess that's why I use them on my scopes). Maybe, you REALLY have to tighten them down on the 30mm set. I will say that I do not like the idea of having 2 screws on each side of each ring. You tighten one, the other becomes somewhat loose. That in itself is a bit nerve racking, especially when one is concerned about over torqueing the screws and stripping one.

You would think that all new, high quality scopes would come from the factory centered. I have performed the scope centering as described, but have always used a cardboard box which doesn't provide the best stationary support. I really like the setup you provided a picture of, and will head off to Home Depot today to pick up some nylon head screws.

If you've any other thoughts, let me know. I do not have a laser bore sighter-it would sure be helpful in this instance. I would really like to use the adjustment bushings that Burris includes in the 30mm ring set to center POA with POI, but that is about impossible without a bore sighter. I just don't like using up a lot of available elevation/windage adjustment in zeroing POA with POI. I would prefer to have the scope in very close alignment before having to use those adjustments. I've heard that you lose the sharpest available image when doing so, although I don't see how.
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Old April 26, 2009, 12:24 PM   #4
SDiver40
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Join Date: November 5, 2005
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I agree with unlcenick on shooting it a few times without adjusting anything. See if the bullet changes it’s impact point.
ALSO if your reloading your own ammo, drop a few rounds down in powder
( 2500 fps ) and see if it holds POA. Some guns just don’t like to be pushed
by the full power loads. My 243 loves the 87gr. And the 74gr. Bullets. ( 3000 fps) But the 100 gr. starts to open up the POA a bit, but not much. How fast
Are you pushing your ammo and what gr. bullet are you using?
Tom
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Old April 26, 2009, 01:07 PM   #5
PCJim
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This rifle is an Ithaca LSA-55, an imported Seiko/Tikka from what I've learned. I can consistantly shoot 100gr Nosler Partitions into a 1" circle at 100 yards with a bench rest/bags. The rounds taken yesterday are Nosler solid base 100gr, hand loaded, trickle charged with 40.0gr of IMR4350 (non-chroneyed). I shoot with the same consistency using 100gr Sierra ProHunter's, which have been chroneyed at an avg of 2794fps with 18.0 sd.

I came across a great buy at Natchez for the Weaver scope and bought it to replace a Fullfield II 3-9x40 that I intend to put on either a newly purchased 10/22 or an AR. After mounting the Weaver scope on the .243 at home, I went to the range and the results were very disappointing. As I said, first shot at 50 yards, without adjustments, was 1/4" above the center "+" of the target. With no adjustments having yet to be made, the shot placement began wildly moving to the right at 100 yds. With major windage adjustments, I was able to get a somewhat satisfactory group before I stopped, but was already using my intended load development rounds which is not something one wants to use for sighting in.
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Old April 27, 2009, 09:50 AM   #6
PCJim
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Join Date: July 11, 2008
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An update....

While cleaning the rifle late yesterday, I noticed the rear receiver screw was loose. Not a lot, but it was not firmly tight, and did allow some slight movement of the receiver within the stock. I'm not confident this was the problem, but it certainly could have contributed.
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