Home Forums Hunting & Shooting Long Range Hunting Lapping rings

Was watching a best of the west show this morning while drinking the ol coffee, and they were setting up one of their huskemaw deals. It appeared to me the were using talley light weights. They were only lapping the bottom half of the ring. I run alot of leupold dual dovetails. I lap with ring tops on and try to get at least 80 percent or so of contact with the scope tube. Wouldn't a guy want to lap the entire ring itself, keeping the orientation or the rings the same as they came out of the package? May be wrong, but I like the idea of only having to lap the bottom half.

I don’t understand why they would only lap the bottoms. I kind of want to hear them explain that reason. I do it the same way you do.

Sounds little weird.
When we did mine, we did top and bottom.
I think it makes a difference

The top of the ring aligns itself without stressing the scope tube since it can move when the screws are tightened, therefore it aligns parallel to the lapped bottom. The bottom is fixed and it's lapping sets the alignment of the scope without stress on the tube.

Now this is not perfect I would suspect and lapping the top and bottom of the rings may give some advantage although I am not sure it would be measurable.

If the top ring isn't round, and that perfect 1/2 30mm circle (or whatever the ID is supposed to be) will it still not pinch the tube when tightened down? It physically can not "self align" because it's not exactly 30mm across or whatever?

I have never lapped rings on any of my scopes and as far as I can tell never had any problems, I usually use Leupold dove tail or standard rings.

I always lapped top & lower at the same time. That is how I have seen some pros do it.

I had a 25-06 that would not shoot decently. I lapped the rings and the difference was nite & day.

Well I use to lap both the bottom and top of the early versions of the Talley Lightweights because of the pinch they built into the ring that was suppose to spring a little when tightening the scope but what happened was the rings just damaged the scope barrel. By lapping those this pinch was removed. I understand the later Talley Lightweights may not have this spring fit today.

Now the purpose, as I see it, of lapping rings is to get the axis through the two rings in perfect alignment so that no lateral torque/bending is exerted on the scope tube. Scope tube diameters vary from one manufacture to another, our own John Barness just recently mention the variations in tube diameters, and I suspect these variations in diameter even exist from models within a single manufactures line. Now you add in that there are variations in the diameters of lapping bars and you can see where lapping does not insure a perfectly round ring. If you start out with the perfect ring and a undersize lapping bar your ring will be out of round and will have more contact pressure on the sides of the scope tube than the bottom. Conversely if the lapping bar is oversize the bottom of the scope tube will have more pressure applied than at the sides.

I would think that this small amount of pressure difference is insignificant in the operations of the scope internals. What is important is that the two rings are perfectly aligned so as to not have a torsional bending of the scope tube. This can be accomplished by just lapping the bottom of the ring which will allow the scope tube to sit as straight as possible without the torsional force of misaligned rings.

I would submit that if rings are perfectly round the chances of your lapping bar matching the exact diameter of your rings or the scope tube to be very slim.

Yea I really don't know their logic. I would not mount a scope in a new set of rings without lapping. Even the talleys. When that scope slides like glass and there are no small friction marks (which can be wiped off) are present I feel it's ready to be leveled onto the rifle. And they used the wheeler level level level deal with the level on the scope turret. I watched a deal about 5 years ago when that dude from Thomson long range mounted a scope. He used a string and plumb bob about 50 feet away to level the reticle after leveling the action. Do that then stick a level on the turret and you'll find what you thought was level is way out of wack. But that's a different story.

When I switched to more expensive scopes I started lapping: top and bottom. I was and am convinced the rings never fit the scope without it.

I have saw this same topic several times over the years. That is the best description of why it is only necessary to lap the bottom ring that I have saw. And maybe, why it really isn't that important to do at the same time.

That being said, I'll probably keep doing both halves when I do it. I don't do it every time and couldn't really tell you why I do when I do, except that it sometimes give me the warm fuzzies. Personally, I've not seen it make a difference in accuracy when done to a rifle of previously known accuracy.

Even the scope tube on my $2300 Nightforce Competition scope vary .003" from end to end...
Lap the bottom rings, bed the scope afterwards. You'll be GTG.

Coyote10: Been lapping rings for several decades now and I only align and lap the bottom halves.
Works well for me.
Hold into the wind
VarmintGuy

Harold Vaughn wrote about this...

Would ring alignment (via using alignment bars) enter into your decision process? I know it would mine

Conical alignment bars are problematic. Turn them around and use the other end

^^^^9point3 is correct on this.^^^ Whoever came up with the idea of using two pointed bars to align scope rings most likely had never mounted a scope or shot a rifle. Putting the square ends together will tell you more but even this can be misleading by a few thousands of an inch. Assuming your lapping bar is straight, meaning less than a few thousands of an inch runout on it, lapping the bottom rings will give you the most accuracy.

If you don't have the 50 feet to work with then level your rifle up in a vice with the butt plate a foot or so from a light colored wall, or big piece of white poster board. Then with the lights in the room off, shine a strong flashlight through the objective lens of the scope. Fiddle with your focus and power until the image of the reticle is clear on the wall. Thumbtack a string with a fishing sinker on the wall as your plumb bob. Level your scope to the shadow of the plumb bob string. Never not works.

I use pads of 3M vinyl electrical tape top and bottom.

Works fine, like they were painted on.

And they release when to caps are removed.




GR

My lapping kit did come with the bars. I have used them to make sure that I was at least ways close but never really trusted them. I do like the idea of turning them around but had never thought to do that. Thanks.