Good idea, I just made a zero stop for my mark 4, I got lucky and found a washer that was just right after I pounded it and redrilled center for post. Guestion, my vari 3 does'nt seem to climb the post as you dial up? How would you zero stop that set up?
That is what I DID,washer on mark 4. I did test with just old plastic butter dish lid, but the allen is a better deal, washer has to be exact, and it is hard to get exact shim thickness.
Which brings up another idea. I read what you said about using a washer and I thought "meh". But I can cut a washer off some brass round stock with a parting tool to any thickness I want. Maybe I'll fiddle with that idea on my other scopes. It will probably give a better feel when it bottoms out at zero. Hhhmmmmm.
When I started I MEASURED on outside of turret to get a idea of shim size, for my zero back to bottom. I used a stainless washer as it was closest to size, hardware store had brass and nylon, if you had the room you could use washer and fine tune w/ allen. I could not tell what base was on mine, I think it was black, I skimmed my washer on belt sander and turret set screw has a small amount of verticule travel, I set turret at zero, applied a little down pressure and tightened set screw. I WILL use allen on future. BUT does anyone have any ideas on my vari 3, it does'nt climb like the mark 4?Which brings up another idea. I read what you said about using a washer and I thought "meh". But I can cut a washer off some brass round stock with a parting tool to any thickness I want. Maybe I'll fiddle with that idea on my other scopes. It will probably give a better feel when it bottoms out at zero. Hhhmmmmm.
I really like your idea lr however heres a thought. there are micrometer type markings under your turret (leupolds with target turrets) with a verticle centerline that indicates where you are clicked to. if you just throw a zero stop (free moving sleeve) you are covering that up and could easily be off one click when dialing a long way could be a miss. thats why the one i have has the set screw. it has a line on it that you line up with the micrometer and tighten the set screws so you dont loose that reference point. so what if you put a mark on yours and found just the right sized O ring to fit under the sleeve to keep tension on it so it doesnt move around. and you dont have to worry ab out marring from a set screw... lightbulb
if you can address that i think you have quite possible the best option around!