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Lost zero after 90 shots--normal?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 00:16
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Just bought a SS 1-4x24. I like it but it has already lost zero on me after 90 rounds. Is this normal? Did I do something wrong? Here's the story:

  1. Mounted scope with Burris PEPR QD on my LMT Defender M4 carbine.
  2. Zeroed the scope at 100yd using 5.56 XM193 ammo. I unscrew the turret caps and set them on zero. Tighten the turret caps back down.
  3. Scope works fine. I fire exactly 62 rounds.
  4. Get home and notice my scope has "slid" forward about an inch! I chalk this up to my inexperience mounting scopes. I remount it with more torque on the rings.
  5. Go back out 3 days later and fire 20 more rounds (82 total). No problems. Scope is not moving in the rings. Hit my target each time.
  6. Go another 10 rounds (92 total) and I start missing my target, a steel gong 7wx11h".
  7. It takes me another 30 rounds (122 total) to figure out I'm missing left. I compensate about 1 to 1.5 mil right using the reticle and start hitting the target again. Vertical zero seems to be fine.
  8. Cease fire and I have to leave. Don't get a chance to adjust the R-L turret.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 00:19
proimion View Drop Down
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Sorry--forgot to add it is a new scope.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 08:06
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How much torque did u put on the ring caps?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 08:06
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over-torqued rings? Too tight can also be bad...affecting scope internals.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 08:10
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Sounds to me like a mount issue, what are you using to confirm proper torque on the rings?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 08:57
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Had similar issue with a Viper PST 1-4x scope also in a PEPR mount.  Use the poor man's torque method of tightening the screws with the supplied allen wrench.  Groups were inconsistent despite using exactly the same ammo/lot.
 
Problem disappeared once I used a torque driver to get the proper specs on the rings (18 in/lbs) and base (65 in/lbs).
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 09:18
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Due to the internal mechanics of a scope it is very highly unlikely that the scope would cause you to miss left. It would be more erratic than just shooting left if the scope was damaged or broke. I would say go back and check the mount and set it to all of the proper torque settings and I would be willing to bet the issue will be solved.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 11:33
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Like Marine24, I used the included allen wrench, so I can't say how much torque is on the rings. I'll get me a proper tool and report back on what happens.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 11:42
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It should only be 15 in-lbs.  That is very little torque.  You can easily do that much with a screwdriver based tool and your thumb and index finger.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 12:03
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Did you use some loctite?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/11/2012 at 14:34
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I think the mount is the most likely suspect.  I prefer the La Rue  mount but  the BOBRO or Badger Ordnance and the Aadland are also a very strong mounts. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2012 at 01:13
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Originally posted by proimion proimion wrote:

Like Marine24, I used the included allen wrench, so I can't say how much torque is on the rings. I'll get me a proper tool and report back on what happens.



For the uninformed what constitutes a proper tool here?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2012 at 03:26
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The proper tool is a wrench that sets exact torque, there are many options. The "short arm vs long arm" method assums many things - and can result in significant deviation from spec torques.

I have the ame scope on an 11" upper, never a problem.

I am a fan of AD and Aadmount mounts. Many assume that simialr design for less money is a win-win, but sometims more expensive mounts are more expensive for a reason. ** i am NOT recommending a new mount as a first step, many run that mount with success.

Start with the cheapest, easiest fix, go from there.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2012 at 04:07
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Like Rancid said, a torque wrench that can set torque in inch/lbs is what you need for mounting scope bases, rings, tightening action screws and a number of other maintenance tasks.  These are valuable tools even for routine maintenance on your weapon
 
This is different from the one I use on my 65 Impala with sets torque in foot/lbs.
 
Lot of different options ranging from traditional long handle torque wrenches, preset torque drivers, torque screw drivers...etc.
 
I have a Weaver gunsmithing torque wrench plus a conventional bar style torque wrench.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2012 at 11:07
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Originally posted by Rancid Coolaid Rancid Coolaid wrote:

The proper tool is a wrench that sets exact torque, there are many options. The "short arm vs long arm" method assums many things - and can result in significant deviation from spec torques.


Any specific tool recommendations?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2012 at 11:43
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Originally posted by castlebravo castlebravo wrote:

Originally posted by Rancid Coolaid Rancid Coolaid wrote:

The proper tool is a wrench that sets exact torque, there are many options. The "short arm vs long arm" method assums many things - and can result in significant deviation from spec torques.


Any specific tool recommendations?
http://www.midwayusa.com/product/718023/wheeler-engineering-fat-firearm-accurizing-torque-torque-wrench-screwdriver
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2012 at 12:51
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Originally posted by Chris Farris II Chris Farris II wrote:

Originally posted by castlebravo castlebravo wrote:

Originally posted by Rancid Coolaid Rancid Coolaid wrote:

The proper tool is a wrench that sets exact torque, there are many options. The "short arm vs long arm" method assums many things - and can result in significant deviation from spec torques.


Any specific tool recommendations?
http://www.midwayusa.com/product/718023/wheeler-engineering-fat-firearm-accurizing-torque-torque-wrench-screwdriver


A good choice.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2012 at 19:13
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http://swfa.com/Borka-Tools-MG3-Multi-Torque-Driver-Kit-P51012.aspx
 This is a much better tool than the wheeler.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/13/2012 at 20:31
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These work really well and accept any 1/4"bit. Usually inexpensive on auction sites.


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/14/2012 at 17:35
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Here's an update from the OP. I got a Wheeler FAT wrench and remounted the scope using 15 in/lb of torque on the rings. I hope to get a chance to get back out to the range soon and see what happens.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/15/2012 at 07:57
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I have the Fat Wrench as well. The specs call for 10-15 inch-pounds on aluminum rings (which I wouldn't recommed) and 15-20 inch pounds on steel rings.
 
I tighten mine in incriments and in a sequence (like the lug nuts on a wheel). I tightened all screws to 10 inch-pounds, retighten in the same sequence to 15 inch-pounds, do it again at 20 inch-pounds. I am a bit anal though . . .
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/16/2012 at 00:51
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Another update from the OP. I re-zeroed the scope today and fired 120 rounds. Held zero just fine. I was able to consistently hit my targets at both 100 and 200 yards with no trouble. I really like the scope.

Thanks for the advice, y'all.

I chose the Wheeler FAT wrench because it was easily available from Amazon and other places and it comes with a nice variety of bits.

I chose 15 in/lbs of torque on the rings, because, well, that's what seemed best. I couldn't find any documentation from Burris that said what torque to use for the PEPR rings. And the Wheeler documentation didn't seem to apply--their recommendations were much higher but seemed to be for larger screws and/or steel rings. So after a lot of searching around, two numbers consistently came up: 18 and 15. Indeed, both were also recommended on this thread.

So I chose 15 and figured if it proved to be too loose, I would try 18. But after 120 rounds, the scope did not move in the mounts and it held zero. I suspect that previously I had it too tight.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/16/2012 at 01:07
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Thanks for the update. Glad to hear it is working for you.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: July/16/2012 at 08:24
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Excellent
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/27/2013 at 22:42
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Bumping a dead thread here, but I found it helpful because I was dealing with the exact issue.

For anyone who finds this thread in the future, I emailed Burris and got the following response -

Hi Rob,

Make sure the ring top screws are torque to 22 inch pound and the cross bolt at 85 inch pounds.
Yup, (I) use LocTite blue on my bases and rings.

Regards,

Brian Fowler
Customer Service Technician

Not sure how to measure the torque on my cross bolt, but will probably go 20 inch pound on the top ring screws.
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