Hoping to find an answer to a chambering problem. I have a Service Model Ace that was manufactured in what I believe was the late '70's. I have had the gun since new, and have always seemed to have a problem with it chambering. The slide seems to fail, more often that not, to go into battery when chambering a round after firing. This has occurred with numerous brands of ammunition, all of which were high velocity, and with different magazines. I am wondering if it has anything to do with the floating chamber or not. It seems I read something a number of years ago that these guns were a little finiky, but I don't remember the details. Are there any lubrication tricks that might resolve the problem. I probably shouldn't even shoot it, since it is minty and in the original box, but it is too much to resist! Anyone have similar problems or solutions?

The big problems with the conversion unit were fouling of the recoiling piston, and less than great accuracy.

The fouling problem was a tendency for the lead bullets to build up fouling until the floating chamber froze up.

In your case, I'd try a new recoil spring, or a slightly stronger recoil spring.
Second, have a gunsmith do a LIGHT polish on the feed ramp in the barrel.
Have the front face of the slide inspected for rough surfaces.
Have the extractor inspected, and if necessary "tuned".  

Possibly the extractor or a rough slide breech face is preventing the cartridge from sliding up the face and is causing a mis-feed.
This is often in the form of "stemming".
This is where the bullet starts to enter the chamber, but fails to feed the rest of the way, and the slide is stopped before it can close all the way.

If you want to just "cut to the chase" and get it fixed NOW, send it in to Colt.  They will get it repaired quickly, and may not even charge for it.

Be sure to FULLY describe EXACTLY how it's jamming, and provide all the details you can without making the letter too long.

thank you sir! I appreciate the reply...