Ok, this is confusing me so somebody please set me straight.  I'm confused about mounting adapters.  

At it's simplest, if you have a device that doesn't natively mount directly to a M-1913 rail then you need an adaptor.  Obviously.

But from what I can tell if you have a device that already mounts directly to a M-1913 rail then you should be able to remove and replace that device at the same position and retain a zero.  ??

On my hunting rifles I don't tend to swap out optics much an the rings screw right into the barrel taps.  However, I found a set of rings with throw levers that will mount right to M-1913.  That should be enough isn't it?

Damn, I know I probably sound confusing here, but I guess my problems is my flattop is described by 3 terms, M-1913, picatinny, weaver.  I'm familiar with weaver.  Does picatinny refer mainly to the pattern of slots?  And why would I need a middle adaptor such as Arms #5 if the device already is weaver ready?  What am I missing here?

Conversely, Arms #35QD makes sense since they are different mounting mechanisms.  

Thanks,

/j

I think 1913 and Picatinny are the same, and more precisely/completely defined than Weaver.  Weaver doesn't necessarily have the cross-slots, or have them in the same place.  Picatinny has the slots in precisely defined places.  

Most things that fit on Weaver mounts are too low for mounting on an AR, so you would use something like the ARMS#5 to raise it up.  The #5 also allows for STANAG mounting, so it could be used as an adapter.

What your trying to find out is does something REPEAT zero. Repeat means taking off and putting back on and going back (returning) to zero. Some call it maintaining zero but that can be misleading as something can also be on a weapon for years and still maintain it's original zero. Hold zero is another term used and generally understood that it is staying on zero without the on and off aspect being a factor. The tightening of thumb nuts is not done with the same amount of hand pressure as a rule (wet, cold, etc. hands)so repeat of on and of of aiming devices is not as precise as lever attachment as the measured spring loaded levers are pulling down and not across. The across direction of force of thumb nuts and allen wrenches which affects windage is more prone to loss of repeat zero.
Hope this helps. Good shootin, Jack