Rifle Scopes shim base?? need answers please

[mm509]

I have been pondering this for awhile.....so here goes. I have a 20moa base on my 300 RUM. I have a Leupy MK4 6.5-20x50mm scope with 70 moa elevation adjustment. I was wondering if it would be feasible to shim my scope base to make my 100y zero the lowest my bullet impact can be?? Since no windage adjustments really need to be made until 200-300y, I wouldn't need to worry about windage travel with my turret buried.
Now the real question is does one think that this type of shim system would cause any pressure in the scope tube? I haven't crunched any mathematical numbers at this yet, as I am trying to decide if it will put any undue stress on the scope. I dont think it will require more then approx .010"-.025" shims. Any opinions will be accepted openly. Thanks

 

[cruizer]

Re: shim base?? need answers please

I would sell your 20 MOA base and get a 30 or 40 MOA base and not take the chance of screwing someting up

 

[Wild_Bill]

Re: shim base?? need answers please

ok that is all feasable to get a 30moa base but what distance do you want to shoot it to? if you are looking for a mile yes get the 30moa base if not going past 1200 yards stay as it is and you will be fine. Just dont shim it as it can bend the mount and if you bend the mount then the scope can get bent.

 

[UNCIVILIZED]

Re: shim base?? need answers please

This may help with the math bit shim wise, & or to either have one made. Or get a machinist to adjust the base which you already have, if you decide not to go with a different base. My only concern with shims has to do with there being more parts to shift around should one's rifle take a good knock. So were it me, bonding it in place at a minimum comes to mind.
Sniper Country In Review Armament Technology 15 MOA Tapered Shim

That said, there are bases made stock from about 10-15 MOA up to say 40 MOA. And other sizes/elevations are available off the shelf, though one has to dig to find them. If you talk to US Optics, as of last check they'd custom make you pretty much anything you want base wise. And if you do the math it's not rocket science to figure the specs on a custom one. The harder part's reaching for your wallet to pay for the thing.

The point about how much elevation do you really need is truly a valid one, especially given that cartridge. Unless, that is, you have a way out of spec reciever & you're using an inordinate amount of the scope's elevation just to get your zero.

If you switch to something like a 40 MOA base, & swap out for a different scope. Or set things up like you're describing for your 100yd zero, & you change glass. The other scope may not be able to get any kind of close range zero. IE: 40 MOA base, & optic with 60 MOA total elevation equals a headache for zeroing. 20 MOA on a .300 RUM is quite a ways out there, particularly as a zero.

 

[mm509]

Re: shim base?? need answers please

It is not entirely the distance I am looking for, although that is an added bonus. I am more interested in establishing a zero stop on a Leupold Mark 4 and gaining the distance is just a bonus. I have access to viable manual/cnc machining equipment and the master machinists to do the work. Me being the welder we trade work back and forth. I have questioned him on just machining the dope into my existing base but remingtons have those 2 different radia on their bases front versus back. So this is why I was thinking a thin brass shim that would mold itself into shape. I do agree with the uneven torque on the base and this is where my concern came into play also.
In closing I was just thinking of a zero stop on the Leupold.

 

[spr1]

Re: shim base?? need answers please

Flat shims would be a bad idea mechanically. You put the screws in a combined bending (the screw heads no longer sit flat in their counterbore) and tensile load situation, and, the base now really only contacts in two spots instead of all along its surface. A lot more to go wrong.

 

[zink14]

Re: shim base?? need answers please

You don't want your zero at the end of your adjustment range, it will put Erector springs under load. If you want a zero stop you are going about it all wrong... Keep it easy and shim the elevation turret or just sell your scope and buy one with a zero stop

 

[bignada]

Re: shim base?? need answers please

Why not just set your 100yd zero on your first dot up from the crosshair? That's basically a snapshot proposition for you anyway, since you're not concerned with windage.

If your Mk4 at max come-up is at 200 or 250yds, first dot up would put you almost right-on.

Going to any base with MORE MOA would just make your problem worse, wouldn't it? A 25moa base will just start you 5moa further out than a 20, or have I been missing something since 1997? (Probably missing lots of shit much longer than that...), but you need Less Cant not more, if you want a crosshair zero at 100yds.

 

[mm509]

Re: shim base?? need answers please

thanks, everyone for all the feedback. Guess I will just bag this idea. I agree with what everyone has said about contact points, eneven tensions, etc. What I didnt realize was the torque on the erector spring.