336 Marlin & 4x Leupold scope issue I need help with.

[Shuz]

I have a fantastic load for my .30-30 336 Marlin that shoots 1/2" 3 shot groups at 50 meters. Problem is, the group is about 2" low and the scope elevation adjustment has reached it's limit. If I put a shim under the rear Weaver base, will this give me more elevation at the target? Thanks,Shuz

[Wolfer]

Yes it will

[cub45]

I would make sure you have the correct mounts, something is not right.

[Texas by God]

Is your load a very mild one?

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[Shuz]

Is your load a very mild one?

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Yes, it is 7g of Unique with a 165g NOE 311-165. Velocity is only 1143fps but the SD is only 5.

[MostlyLeverGuns]

If using the Weaver one piece base a simple shim under the rear base will work, though I would bed the entire bed with JB Weld to keep the base straight, don't glue the base to the rifle, use a release compound, like Johnson's Paste Wax on the receiver. If you are using a 2 piece base, simply shimming the rear base will cause the rings to go out of alignment. Burris Signature Rings with plastic inserts can prevent this. The right set of inserts could take care of the entire problem. The very mild loads are probably why a standard mounting setup is not working.

[Texas by God]

Take your elevation dial all the way to the other end while counting turns or clicks and come back halfway. Now try to sight it in again.
Sometimes voodoo works.

[Shuz]

According to the Weaver chart, the one piece base I have is the correct one they list for a 336 Marlin. I did turn the base around and re-mounted it to see if that makes any difference. I may try Texas by God's voodoo trick and see what happens. I did find that I had put a .006" piece of beverage can under the rear screws, and I was still low with my load. Maybe two thicknesses would do the trick?

[pietro]

.

FWIW:

Some scopes have a difference in adjustment range between the windage & elevation adjustments.


Often, successful zero can be reached by simply rotating the scope in the rings 90-degrees, making the former windage adjustment into the new elevation adjustment - and the former elevation adjustment into the new windage adjustment..



The old elevation/new windage turret will simply lie outside the LH side of the mount, ILO a turret hanging over the ejection port.






.

[fiberoptik]

.

FWIW:

Some scopes have a difference in adjustment range between the windage & elevation adjustments.


Often, successful zero can be reached by simply rotating the scope in the rings 90-degrees, making the former windage adjustment into the new elevation adjustment - and the former elevation adjustment into the new windage adjustment..

.

I was going to suggest the same.


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[Texas by God]

Pietro is on it! I've done this, too.
The mantra is "up-right& left-down".

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[Uncle Grinch]

I could be “all wet” but I believe if you wanted to shim your scope base to raise a low impact group, you would shim the front not the rear. Shimming moves the cross hair relative to the “image” in the scope.

If I’ve got my head in my duffel bag, someone please let me know.

[NSB]

Get a set of Burris Signature Zee rings with the plastic inserts that allow raising or lowering the scope as needed without shimming. They're also an outstanding set of rings even with "zero" inserts. Shimming is not always the best thing to do (although I've done it myself). It puts stress on the scope tube in the same way that rings can do if the receiver isn't flat and the rings are out of alignment. Just a thought....

[mac60]

Take your elevation dial all the way to the other end while counting turns or clicks and come back halfway. Now try to sight it in again.
Sometimes voodoo works.

TBG is right. There's no way you should be running out of adjustment. The basic problem is you're putting the scope on the rifle with the adjustment near it's limit - not leaving room for adjustment.

[Gtek]

How tall are the mounts? Lower mounts?

[pietro]

I could be “all wet” but I believe if you wanted to shim your scope base to raise a low impact group, you would shim the front not the rear.

Shimming moves the cross hair relative to the “image” in the scope.

If I’ve got my head in my duffel bag, someone please let me know.

Get a towel, Uncle Grinch, and dry off...…..

Shimming a rear scope mount base does nothing to the reticle, it will merely tilt that end of the scope "up" when it's raised, thereby lowering the POI and/or bending the scope main tube slightly (if the mount isn't a 1-piece/rail), just as when adjusting iron sights.


.

[Uncle Grinch]

Get a towel, Uncle Grinch, and dry off...…..

Shimming a rear scope mount base does nothing to the reticle, it will merely tilt that end of the scope "up" when it's raised, thereby lowering the POI and/or bending the scope main tube slightly (if the mount isn't a 1-piece/rail), just as when adjusting iron sights.


.

Thanks for setting me straight. I finally found some info on shimming to validate the proper technique.

[MostlyLeverGuns]

With the long 1-piece Marlin base (63B ?) Shimming the rear higher will lower impact. You can tighten the front screws to the point where the base will flex, with forward unsupported section moving upward slightly and you will lose some of the shim benefit. The reason to bed the entire base is to avoid this flexing, with the front base screws just snug so as not to distort the base until the bedding compound hardens. I would start with a .01 shim. Again the Burris Signature Rings resolve many issues when mounting scopes. Burris does make a Zee Ring in the Signature(shim) style that fits Weaver bases.

[Texas by God]

Or just try a different scope.

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[Shuz]

Well, I took a piece of copper of .044"thick and shimmed the rear base. I had to use 8-40 1/4" screws to reach the receiver holes instead of the original 8-40 3/16" due to the tremendous thickness. This may be way too much of a shim, but it was all I could come up with at the present time. We have shooting restrictions in place right now in Washington state due to the fire situation. It may be awhile before I can report the results. I also took the elevation adjustment all the way down and back up about halfway to start.