You know why gunsmith's loved series 70 Colts? Because they were the ones least likely to work. Also, until CNC became affordable for people other than large, long established manufacturers could afford the technology, Colt was by far the best game in town; even at their worst. Trust me, I worked at Vega!
Series 70 internals were strong parts that were actually made to spec. But they were FAR from smooth or consistent. Colt's barrel fitting left MUCH to be desired, and their solution, while clever; just failed. The '70's and early '80's were ROUGH economic times. Economists didn't know how to deal with inflation like we do now, so it just kept going, and going, and going. That VASTLY reduces disposable income for things like Colt's. Colt had high labor costs, high taxes, VERY worn equipment... They just weren't at their best. I'm not saying Series 70's were bad guns, far from it. They were just FAR from Colt's best effort, in fact...I think it was their worst effort, just my opinion, and I think Series 80 guns were just better...even with cast parts <GASP!>. Even at their worst, there are some absolutely stunning Series 70 guns out there that I'd commit many crimes to get my hands on. I LOVED how Colt did their bright nickel guns during the Series 70 era, those are so cool.
As a gunsmith who worked mostly on 1911's, I found Series 80's with their newly re-designed feed ramps considerably more reliable, and more reliable with more types of ammo. Barrel fitting was consistently better. Metal polishing was different, but WAY more consistent. It was a bit lower grit level of polishing, but I found it to be more consistent, with straighter lines.
Series 80's were dubbed inferior "cast" guns. When in fact, not much was cast metal. Hammers, slide stops, barrels, frames and slides continued the old school processes. The cast parts were all the non-critical, low failure rate parts...and Colt got it right. Series 80's parts breakage or parts failures are really not significantly different from any other series.
Gun people are passionate about their favorite Roscoe's, and they get offended when people go changing their favorite things. High passion, low coping skills/tolerance to change.
Yes the start up years of IPSC, get and use what ever you could get your hands on. Bet you know what a Cariville Arms safety strap is. Probably the first Beavertail ever made. Used one on a Nat. Match for early IPSC.
