re:
Hi Sport,
In this statement:
> It's like the slide is riding over the rim and catching the round in the middle, if that makes sense. Once in a very great while a tap on the back of the slide will finish chambering the round but that is the exception, not the rule. This seems to...<
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You've described two different malfunctions. The first ( Seems to be riding over the rim) is known as a "Rideover Feed" in which the round isn't in feeding position when the slide meets it. Related to the "Bolt-Over Base" but not exactly the same. The rideover is a true failure to feed in which the round is usually firmly jammed against the feed ramp with the slide on top of it. The Bolt-Over results in the cartridge standing straight up in the port, caught between the breechface and the barrel hood. Also a true failure to feed,
and a potentially dangerous one. Both these stoppages are caused by the magazine, and most often by a weak or damaged spring. A heavier recoil spring aggravates the problem because it speeds the slide up on its return to battery...and it's actually outrunning the magazine. The cure is usually a good spring. I recommend Wolff 11-pound mag springs.
In the second, where you describe being able to tap the slide and chamber the round, you're describing a failure to go into battery. Since you've said that the gun used to be dead reliable, we can eliminate rough breechface
and stem bind (3-Point Jam) and turn our attention to the extractor. Because it was once reliable, excessive tension isn't likely the bug.
Remove the extractor and clean the channel thoroughly. Clean the breechface with a solvent-wet brush, and use a toothpick to get into all the nooks and crannies that the brush can't reach. Extractor removal on a Series 80 Colt is a little more involved than on a pre-80, and must be done in proper sequence. Instructions are available on the Gunsmithing forum, contained in the sticky thread titled "The 1911 Clinic." (Series 80 Detail Strip)
That SHOULD solve the return to battery failures. If you have Rideover or Bolt-Over stoppages, you need a new mag spring.
Luck!