338 Win Mag vs. Leupold/Zeiss/Kollmorgen. Leupold NO!

[papabear]

I have a short story to tell you guys might find interesting, and two questions at the end.  

Story first.  I put an old Kollmorgan 4x and weaver cross slot mounts on my new Win. Model 70 338 Win Mag.  temporarily.  It grouped fine.  That old Kollmorgan has been on many heavy recoil guns, from 12 Gauge slug guns shooting premium sabots, to 54 cal. muzzleloader, and has never failed.   I replaced finally with a new Leupold VX III, 2.5x8 x36mm, in dual dovetail mounts.  It was several months later that I tried to work up a moose hunting load with factory ammo.  Nothing worked.  Erratic, sometimes 3-5 inch groups.  I tried everything on the rifle, bedding, free floating, action screws, etc.  I knew my mounting job was secure and I would never doubt the Leupold scope, as I use many of their products.  

Finally, I decide it must be the mounts or scope.  Ring screws were of course checked early on.  I remove the top 1/2 of rings to check the base screws.  They are tight. Oh, I probably tightened maybe 1/16 to 1/8 turn on the front base.  I replace the scope with a used Zeiss Diavari C   3x9x36 I had just picked up at Cabelas.  The rifle groups 1 to 1.5 inches with all loads I had tried before!  

The Leupold was sent for repair today.  I could not believe that it failed under that 338 recoil, but evidently it did just that.

Question 1) Is it possible that tightening front base screws that very small amount was the problem rather that the scope?

Question 2) Can you tell me anything about the Diavari-C Zeiss, what is the quality comparison to their scopes made now? - I got a good deal I felt for $299 used, and seems as good or better than Leupold for light gathering at same power, but I guess it is not made any more.  I found it in 10 year old Gun Digest, but that is all I know.

Thanks, I enjoy the forum.  When all else fails, I usually find the answers here.

[Redhawk1]

I guess it could of been the base screws, it does not take much movement of the scope to throw off your bullets. A little movement at the scope is magnified out a lot at 100 yards. What did Leupold say about the scope?

I don't think the 338 is to much recoil for the Leupold. I have them on a 375 H&H and 416 Rigby.  

[papabear]

They have probably just received the scope yesterday or today.  I will hear from them soon and will let you know.  

I would describe the front base screws as tight, but the little bit I tightened them was kind of between "I can go a little more" and  "I will break the wrench or screws if I go more".

[papabear]

Redhawk 1, which Leupold scopes do you have on those fierce recoiling guns?

[Redhawk1]

Redhawk 1, which Leupold scopes do you have on those fierce recoiling guns?

I have a Leupold VXII 3X9X40 on the 375 H&H, a Leupold VXII 1X4X20 on my Encore 416 Rigby. I have Leupolds on 95% of my guns. My Ruger #1 has a Leupold VXIII 1.5X5X20 on it and my Tikka 300 Win Mag has a Leupold VXIII 3.5X10X50. Those are just the heavy kickers.  

[Dave in WV]

papabear , yes that little bit you tightened the base screw could have been the problem. The only way to have known for sure is if you had put the Leupold scope back on. It is surprising how little it takes to get a big change when dealing with optics. As for the scope letting loose so soon, one of the gun writers commented in an article he usually saw scopes break in the first 100 rounds fired or they seemed to hold up a long time. Brand or price didn't seem to matter in his findings.