Impact shift after removal of QD scout scope on Marlin1895GS

geologist

geologist

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I took my scope off of my Guide Gun the other day. It had been sighted in for hunting with Hornady Leverevolution 325 gr at 2040 fps, 2.75" high at 100 yards.

The scope is a Leupold IER 2.5X mounted in low Burris Zee QD rings on an XS scout mount.

I previously painted the ring attachment points on the mount in red paint so that I would re-mount the scope on the same location on the rail.

I shot the group at 100 yards on a very calm, sunny day off of front and rear bags.

The group shifted 3.5" right from my previous zero. I was surprised by how large the shift was as previously the shifts had been 2" or less.

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I dialed in the corrections and just to make sure that the shift was not my shooting, here is the first correction with 12 clicks left.

group2_zps443b8d99.jpg


I adjusted it up a bit as well for hunting afterwards.

Overall the shift would not have meant a miss on deer sized game at 100 yards but I sure won't be taking off the scope in the middle of a hunt unless I really need to.

Has anyone else checked the shift in their QD setups? Are they of the same size?

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I've got a set-up much like yours...a Marlin SBL with a Burris scout scope mounted in Leupold QD rings. Removal and re-assembly usually returns me to within 1 MOA if I try to keep roughly the same torque on the ring levers. Several other guns with similarly-designed QD rings give me similar results. The only QD system that I have found to be significantly better is the Blaser, but a base and rings for that runs about $450 so it had better be good! Even with the Blaser, I still can't bring myself to just put the gun together and go hunting...I want the confidence that comes with test firing after reassembly.
 
That is a huge shift for steel rings on a one piece rail, assuming it was perfectly zeroed and you removed and replaced it and you got a 3.5 moa shift
 
rgv said:
That is a huge shift for steel rings on a one piece rail, assuming it was perfectly zeroed and you removed and replaced it and you got a 3.5 moa shift
Click to expand...

I agree. I am going to try it again and while I have the scope off I'll check the mounting screws on the XS mount. I loctited them so I think they're OK.

I had maybe 4 days of hunting on the setup prior to removing the scope but I didn't bash it on anything to move the zero.
 
Make sure your Butler cap isn't sitting on the rail...Also have a look at the back corners of the XS mount where it overlaps the reciever....I had to file a radius on the back side of both of my mounts. If it's touching you may be twisting the rail as well.
 
Colquhoun said:
Make sure your Butler cap isn't sitting on the rail...Also have a look at the back corners of the XS mount where it overlaps the reciever....I had to file a radius on the back side of both of my mounts. If it's touching you may be twisting the rail as well.
Click to expand...

The occular cap is resting on the rail, I never thought of that. I'll cut away a chunk of it and try again.
 
Some things may be hard to find a cause for. I imagine its possible that slight variations in tolerance mean that matching one pair of rings to bases works better than another pair. I also haven't done it that often, so I could be in for a surprise next time I try.

Is it possible that the rings aren't perfectly aligned, and tightening somehow torques and distorts the base or scope?

How rigid is that scout mounted base?

The OP's experience kinda defeats the point of having QD rings.

Nice receiver sight, though.
 
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