Ron,
I believe your bases have already been "skim"milled to level them(when orig. installed).It would be very difficult to scrape them in level, and milling them level is easy(they have to be close though, or milling removes too much).The bases are not often the same height, just as you thought;this is where the boresighting/measuring distance to base comes in.The chord isn't used to tie the scope to the adjustable block,rather it is to fasten the scope to the rifle, with the block trapped between( you need to be able to remove the block to adjust it).
The depth gage at the end of the caliper(or any other type)is used to measure from the top of the base to the top of the barrels,through the opening for the foot.Measure to the lowest spot,mill the foot to this length, then contour it to approximately fit the barrels.The foot should't bear on the barrels, though, or it may interfere with other fitting.
Once the foot is fitup(the slider and springs should have been removed for this operation),you can reach in through the slots on the side and scribe a line on each side with a sharp scriber.If you don't have one, it can be easily made.
If you can find a gun with clawmounts that have been mounted in Germany, or by a Germany trained gunsmith, inspecting it closely can help you a lot, to see how deep to make the slot in the foot for the slider,the angles, etc.The trouble with learning through trial and error is that the cost of the error can be pretty high, if you have to buy new parts.Let us know how it works out, and as always, I'll do what I can to help.
Mike
Mike, I believe most of what you said in your last messages makes sense to me. But I just want to clarify a couple of points to make sure. When the bases are skim milled is the front base skim milled with or without the dove tail plate installed? Or is just the dove tail plate (base) that is skim milled? In my case this was already done when orig installed but just trying to make sure in case I do another set sometime? Just not quite clear on the skim milling and trying to understand it.
The clarification on the chord makes sense. It is simply used to temporarily attach the scope (in the rear portion) to the barrels so the gun can be boresighted by actually firing the gun at 100 yrds. I may be wrong but I assume this is to get the scope close to correct so that the scope has enough room to adjust it internally using the elevation and windage dials. The scope and gun need to be boresighted (and installed close to correct) to ensure that you do not run out of internal adjustment on the scope dials. On my install I thought about this but pretty much just used a long straight edge to make sure the scope was installed relatively level with the barrels and looked appropriate. I also did some testing using a bore sighter (not laser) and it looked like I was going to have the scope close enough that I could complete the scope adjustment using the scope dials and not run out of movement room. Also, I felt it was important to have the feet on the front ring installed fairly parallel to the front base if that makes sense. In other words I wanted the front feet to sit parallel to the front base and this limited how much I could raise or lower the scope in the back. I could see how you could make minor adjustments though.
A very helpful tip on the feet and what they should bear on. I have been trying to make the rear foot bear on the barrels as well as the bottom of the ring and I even thought that possibly the foot bearing on the barrels was the most important bearing. So, I will now shoot for having the feet close to the barrels but have the rear scope ring bear on the rear scope base. In other words the flat area that surrounds the foot will bear on the rear base. I assume that having this done well helps to ensure that the scope returns to zero each time it is removed. And as Oskar noted if the foot is bearing on the barrels all it would take is a little dirt to get in the slot and then this might affect the return to zero.
I'd like to examine a completed set of claw mount scope rings that were done correctly and I can see how that would help. At this point I have only been able to examine photos I have found on the internet of claw rings and bases. I'll keep looking for better examples though.
And yes, trial and error can get expensive. I have ruined at least (2) sets of front and rear bases but have been able to use my TIG welder to add metal in the appropriate places and put them back in service (and start over).
Again thanks to everyone for this very helpful thread. Makes the learning process easier and when I get a set of rings "good enough" I'll post a photo. Might be awhile yet though!
Ron
