They started with the Valmet (412 I believe?) then the Tikka (mine is a 512) and finally the Finnclassic.

The barrel sets of all are interchangeable but may need some minor gunsmith adjusting. The instructions are here on NE.

I have a Tikka 512 SD in 9.3x74R/9.3x74R and 12g/12g. I have used both quite a bit.

Reasonably happy with them. The DR sets have a couple of wedges allowing self-regulation which wasn't hard. My 9.3 was VERY accurate, two one hole groups of 2 shots from each barrel. Impact was parallel to each other as I set it up to be.

I had one problem where on one hunt, when test shooting them, the regulation no longer seem accurate. In Namibia. Back home, re-tested if I remember they weren't bad again. ???

I also have a couple of combination barrels of 12g/rifle barrel plus another DR set. These need fitting still.

I purchased some sets of rubber "spacers" for insertion between the barrels. Haven't shot them since fitting these to see if they had any affect yet. Also a twin trigger set to replace the single trigger, still to be fitted. Plus some extra mounts.

For the prices I paid, not a bad system of multiple barrels and very usuable. Mine has killed a fair number of water buffalo, donkeys, scrub bulls, horses, pigs, deer and warthog. So far.