Advanced Marksmanship Reasonable expectations for holding zero

joshn

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Dec 2, 2006
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As I was going shooting the other day, my scope took a decent bump on the side on the way out. I didn't think much of it at the time, as I thought I had a pretty durable setup. It's a remington 700, EGW base, TPS rings, and an IOR 3-18 FFP scope. I set up shooting at 100 yards, shot a group, and found that my zero was around 3" left. As a test, I wacked the scope on the right side of the objective and then it groups about 5" to the right. It's hard to quantify, but I'd estimate the force of my wack to be similar to what it might sustain if the gun dropped 5" and landed on the objective. So, I swapped rings, scopes, and guns, and I was able to reproduce the problem in every configuration.

So, I thought I'd run this test on other guns. In testing 7-8 different rifle/scope's, they all moved to some degree, ranging from 1-6". And we're not talking barska scopes and $10 rings. Scopes were a couple Leupold mark4's, varix-3, zeiss conquest, IOR, falcon menace, Nikon buckmasters. Most of the rings were TPS, with a warne and leupold in there. The setup that moved the least (only about 1.5"), was a DPMS SASS with yankee hill riser, tps rings, and mark4 scope.

So I guess my question is, is what's a reasonable expectation of a rifle/scope setup hold zero under impact? You certainly want to have confidence that your rifle wont change zero just from the common jolts it may receive in transport. Real-life anecdotes would be appreciated. Thanks
 

ewoaf

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Jan 25, 2009
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Re: Reasonable expectations for holding zero

depends on what setup you are running... some mounts and optics are more reliable than others, you get what you pay for.
 

HillbillyfromAL

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Aug 16, 2009
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Re: Reasonable expectations for holding zero

Which rings do you have exactly? Are you running a picatinny base with weaver style rings? Here's an example of what I mean right off the TPS website:
Right Rings - Right Application We have an extremely diversified line of scope rings to perfectly match the application that you need. For those needing Mil-spec mounts, our TSRTM Series rings are designed specifically for Mil-STD 1913 (Picatinny Rails). For those needing the durability and looks of a tactical ring, but wishing to mount them on a Weaver-style cross-slot base, we offer the TSR-"W" SeriesTM. And those looking for the quality and durability as well as a more sporting look, we offer the HRTTM Series scope rings.
It may not matter to the guys that shoot minute of barn but they aren't made to work together. That would cause exactly what your talking about. Other than that I couldn't see much else causing it other than a problem with the base not being torqued properly/needing bedding. Good luck and let us know what the problem was.
 

Greg Langelius *

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Re: Reasonable expectations for holding zero

I had that happen once.

Turns out the mounts weren't moving, the tube was subtly bent, and bent, and bent. At that point, I figured there was little more to lose and did some judicious rebending until the POI came more or less back to its normal location, and then left it well enough alone.

Kinda wonky, but it worked and it stayed 'fixed'.

Greg
 

joshn

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Dec 2, 2006
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Re: Reasonable expectations for holding zero

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HillbillyfromAL</div><div class="ubbcode-body">Which rings do you have exactly? Are you running a picatinny base with weaver style rings?</div></div>

There are some standard TSR, and some TSR W's. That's a thought, I'll keep it in mind.

Greg, how did you determine that your scope was bent?

Would it be possible that the shift is inside the scope? Possibly the windage mechanics slipping?
 

Greg Langelius *

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Re: Reasonable expectations for holding zero

I was bent enough to see. Talk about an "Oh, Merde..." moment...
 

HillbillyfromAL

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Re: Reasonable expectations for holding zero

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: joshn</div><div class="ubbcode-body"> Possibly the windage mechanics slipping?</div></div>

Not on a quality scope of any kind.
 

azimutha

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Re: Reasonable expectations for holding zero

I once slipped on a snowy rock and hit my scope hard enough to leave a bruise on the inside of my arm as the rifle hit the ground. It didn't effect the zero at all. This was a NF scope in a NF DirectMount.