Ge600/MEC/Unique/Esprit Carabine. Free floating barrel???

[Hemmers]

All pretty much true, but how much has the tech improved the accuracy of the barrel/action.

A lot, actually! If you pick up a random 1913 Anschutz from the last 10 years and take it to Eley, you'll probably get some very good groups. Also some wide open groups. The last time I tested my Supermatch (bought new in 2007) it ranged from 15.5mm to 22mm, which Martyn reckoned to be perfectly normal - obviously 22mm is not even holding the 10 ring.

A modern KK500 or Racer3 will not only group to <14mm, but the worst groups are unlikely to be >17mm. They're not only more accurate, but more consistently accurate over a range of ammunition.

Of course you can find good examples of older rifles - the Olympic Prone champion (Henri Junghaenel) used a Walther KK300 in Rio - but it was the sixth KK300 he'd tried. That's the choice you make - spend a lot of time and money working through barrels to find a sweet one, or just stump up for a KK500 or Racer3 knowing it'll shoot well out the box (and if it doesn't you send it back and ask them to send you one that works).

Of course, if you're only shooting integer targets then the advantage is less apparent - if you've got a batch of ammo that groups well, it'll slug in 10s all day long - and a 10 is a 10, whether it's a 10.0 or a 10.8. For integer purposes, there are lots of rifles that are "good enough".

Stick it on decimal-scoring electronics however and the difference becomes very apparent - the top barrels will shoot 640+ decimal, older barrels will struggle to crack 630.

The new breed of short-bolt actions are objectively more accurate and less picky about ammo. But depending on what you're doing with them (integer/decimal) and your own expectations based on your standard of shooting, you may not notice the difference.