I'm certainly no expert, but, from what I have learned: Colt quality has supposedly deteriorated over the years. The older ones are built better regarding fit/finish. The difference between Series 70 and 80's is the presence of a firing pin block on the 80's that adds to the complication of the mechanism, and the linkage of the trigger. The trigger pull on Series 70's is unsurpassed, except by some expensive target guns. Mine is light and absolutely crisp, without paying $ to have it worked on. I did pay $215 to have the ejection port lowered/fluted, one piece guide rod, bbl. bushing fitted to it, slide rails peened to tighten it, extended/tuned extractor, Wolf mainspring, feedramp polished, throated to feed HP's. It still needs sights as the factory ones are very poor. After having the above done the pistol will not jam, even with $5.00 gun show mags. I strongly prefer Wilson/Rogers mags, they make the pistol function slick as snot on a brass doorknob. Others like the McCormick Shooting Star mags, but put them side by side, test them, and you decide. They cost about the same. Mags matter, as with AR's.