Hello the CAmpfire!
I have an ex Gov Colt in .45 ACP that has been rebarreled with a match barrel and link. It shoots great except that every second or third ahot the slide stop slips up and stops the cycling. It is just as if the mag. were empty, but it is not. Between stopages it feeds any thing I put into it. When I thumb the slide stop down, it chambers the next round and fires with no problems. Any suggestions?

Judge Sharpe, a poor widows son

First eliminate the obvious. Make sure that your not pushing the stop up with your weak side thumb.
That usually eliminates the condition about 95% of the time.

The only thing that should move the stop in the up position is the ledge on the mag follower. You can load some dummy rounds into the magazine, slowly cycle the slide (easier with the recoil spring removed) and see if the slide stop tab is being moved up by a round or something else that shouldn't contact it.

Check to see if it only happens with one particular magazine first. I have seen where magazine lips would be open too much and rounds would come up at an angle and hit the slide stop.
I have also seen guns where the slide stop had excess protrusion into the magazine well area. In a couple of them the stop stuck so far into the magazine well that the next round coming up would hit it.

Also check the strength of the Slide stop detent spring (That's the spring in the little tubular housing on the left side of the frame) It could be bust.

Pete

Good advice above.
I've seen some 1911's where a cartridge can contact the slide stop enough to lock the slide back prematurely.
If you remove the slide, insert the slide stop into the frame, then insert a magazine with a dummy round loaded the relationship between the cartridge and the slide stop can be easily seen.
There needs to be clearance between the cartridge and the slide stop, but not so much that the follower doesn't contact it when the mag is empty.