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Dave,
It is a bond that forms. I remember Russ Carniak speaking of his guns "returning home" when they came back for accessorizing or trade-ups.
Shorts,
I think my middle-aged brain is missing something here. You said the lockup is 0.050" to 0.055" with or without the link, a difference of 0.005". Then you say there is a difference of 0.018-0.020"? Is that what you get pushing the barrel up into the slide with your thumb? Can you clarify what this is a difference to?
One more test to help clear it up:
Coat the link in Magic Marker, then put the link, barrel, try-bushing slide and frame back together with everything lightly oiled. Also lightly oil the assembly pin and insert it through the link, then put the whole gun in the vice again. Put the 3/8" dowel rod back in the barrel and hang enough weight off the end of it to tip the barrel up into battery when the link isn't there (you may have to try this without the link to get the weight right; an empty milk jug with a few cups of water in it works, but be sure the gun is gripped firmly enough in the vice to hold it up.)
Push the slide fully into battery with your left thumb, then let go. Gently place the tip of your index finger at the back of the ejection port so it bridges the slight drop-off from the back of the port to the back of the barrel hood, and is touching both. Use your other hand to carefully sneak the assembly pin out without disturbing the slide position. Did you feel the barrel come up? Now shine a light through the assembly pin hole and tell us whether the bottom edge of the hole in the link remains lined up with it? If you try to sneak the assembly pin back in, does it meet any resistance when it gets past the thickness of the side of the frame and starts to enter the link hole?
If there is any obscuring of the assembly pin hole by the link, push the tip of the assembly pin into the frame just far enough that you feel it kiss the link, but without disturbing it. This is just to keep the link from moving while you perform the next step: Go in through the assembly pin hole on the opposite side of the frame with a straight pin and scribe the perimeter of the assembly pin hole onto the Magic Marker on the link. Pull the whole thing apart and measure how far the scribed line is from the edge of the link hole on the side opposite the web between link holes. Your new link needs that much more web than you have now. You also have short link lugs if these test symptoms happen, but let's not fret that yet. The first step is getting the link length established.
The other approach, if you have a lockup discrepancy and can't get the measurement satisfactorily, is to buy a set of long links and just keep trying them larger and larger until you find one that prevents the gun from passing Dave's gravity test, then back up one size. The only snag that can arise is that a really long link (should your lockup require it) may be so long that it swings the back faces of the link lugs into the frame before the barrel is fully in counter battery. You can identify this condition by assembling the link, barrel, frame and assembly pin (no slide), and observing whether the barrel still seats snuggly back against the frame? If not, and a gap appears between the frame and the underside of the barrel at the rear, then the back faces of the link lugs have to be filed forward until it fits.
Nick
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