Lapping scope rings

[Freakazoid]

Can someone please explain to me what this is and when/where etc it should be done etc.
Thanks

[deonh]

Can someone please explain to me what this is and when/where etc it should be done etc.
Thanks

Oddly enough, I was at the range today, where a buddy was mounting a scope, which would've worked if he had lapped the rings. Like barrel break-in, some folks say that lapping is a waste of time. I believe that lapping has benefits. And even if it doesn't, it can't do any harm. Some folks say that top-end rings don't require lapping. Some folks also play the lotto.

From what I've seen, lapping ensures ring-concentricity, prevents scope / ring misalignment and increases structural integrity (esp. for two piece bases) of the scope / ring / rifle interface. Basically it keeps things straight and steady between all the contact surfaces. Over and above that, you also keep the rings from scratching your scope (a happy by-product).

The "where" is easy. Take it to a reputable gunsmith. Lapping is not rocket-science but does require some know-how and the correct tools.

[wrm]

http://www.boothroyd.co.za/?p=102

But even when the bases are the right ones for the rifle, and are properly fitted, manufacturing tolerances in rifles and mounts guarantee that the rings will always be out of alignment until they are lapped. Of the many I have fitted, I have not found a pair that was not out to some extent. The amount is usually too small to see, but one or two thousandths is all it takes to allow scope slippage, because the rings don’t grip the scope securely. I have seen the finish scraped off by the sharp edges of the rings, and scopes dented by over-tightening misaligned rings.

[Freakazoid]

Ok well I got a one peace rings base that was manufactured by the same people as my rifle do I still need to do this?

[Dick]

I tried to answer this earlier, but got told that I was not allowed because I was not logged in. But I was logged in. So this is a test because I don't want to write all that again for nothing.

[Freakazoid]

Piece not peace lol damn phone

[wrm]

A trick I use after typing a long piece of text into one of these forum things is select all, ctrl-C (copy). Then if the post goes awry you can flash up notepad and paste it in there.

Not that I always remember to do this...

[Dick]

OK, now it seems to be working. It is all explained in detail in my book. I ought to be cross that no-one wants to buy it, considering how often this question comes up, as well as sighting in. But what the hell, here goes.

Engineered items like firearms and motor cars can be made to close tolerances quite economically. But making them to absolute perfection, zero error at all, is so much more expensive that it is a trade off between cost and quality. In essence, such things are made accurately enough for purpose, but money is not wasted on making them even more precisely if there is no measurable benefit for the extra cost.

That guarantees that rings will not be perfectly aligned ie perfectly concentric with each other and on the same axis, unless they are lapped. They can lean backwards, forwards, sideways, up or down, or a combination of all. I never found a pair that was OK.

It is done this way : the rings are fitted to the rifle as accurately as possible and tightened down. A one inch diameter (or 26mm or 30mm) precision machined rod is coated with lapping compound (fine abrasive) and run lengthwise back and forth in the rings. It takes off fine amounts of metal and leaves the rings in perfect alignment. That's lapping.

I do it differently. My method is theoretically less precise, but in practice it works as well. I use a rod slightly smaller than one inch with wet or dry abrasive paper wrapped around it. The diameter of the rod allows for the thickness of the paper, the whole = one inch. I use various grades of paper depending how much metal must be removed. The principle is the same as lapping.

Why is it necessary ? A ring relies on friction to grip the scope tube. That needs 100% contact of the surface of the ring to the tube. If the ring is slightly out it will grip the scope with only one edge. That is not enough contact to grip the scope adequately, no matter how much it is tightened. It is common for scopes to slip in recoil, and for the edge of the ring to act like a scraper and scrape the finish off the scope. It is a point load, so attempts to further tighten the ring to prevent further slippage can dent the scope, much as a woman's stiletto heel can damage a floor. I have seen several expensive scoped so damaged and have photos of some.

The solid contact of lapped rings can be felt as the scope is dropped in. The contact is very secure, and prevents slippage and damage.

Not many dealers, gunsmiths or individuals do it. Maybe its too much work. Fitting a scope properly, that includes lapping the rings and bore sighting, takes two to four hours. I have found that it is often scoffed at and declared unnecessary. But I've seen it and done it. You be the judge.

[Dick]

Ok well I got a one peace rings base that was manufactured by the same people as my rifle do I still need to do this?

Yes.

[deonh]

Uhm... what he ^^^^ said.