Add AGT Uragan 2 .30 (700mm) to your list. Last holiday season treated myself to Vulcan 3 and Uragan 2 Synthetics, in that configuration, enjoy both for longer ranges, no tinkering required. Find Uragan 2 more pleasant shooting, smoother, quieter and less harsh. WM
I concur with
@WorriedMan, the U2 is a very capable slug gun.
How does the original Uragan (1?) compare to the 2 for a slug gun? I've seen a 600m setup that's in like new condition and well priced but I know some CZ barels are choked, while the majority usually are not. Not to hijack the thread but if anyone has had experience with both, let me know.
Anyways, on the topic,
@MikeAllen I have been in a similar situation was looking at .30cal sluggers for similar use. I've heard the Taipan Vet 2 Tac has a GREAT trigger, I've heard the Vulcan 3 is just amazing all around, and I've heard the Uragan 2 also falls into the same category of great CZ slug guns.
As far as caliber, .25cal isn't bad if you want to save a bit of money on ammo, but I personally prefer a .22 for more ammo/slug options, or just go straight to a .30cal as the JSB 44grn pellets are just fine for plinking but there are also some great .30cal slugs out there (I always use Varmint Knockers, who makes a great 62grain HP) and if you are looking for it to double as a competition gun (I assume bench rest, and not FT) then .30 is probably the way to go.
I personally have been also looking at the Sidewinder (compact) and a Krait (standard/compact size) but if you are okay with not shooting offhand you can get the full size versions, the Sidewinder has an amazing TJ Barrel which is great for slugs and the gun is completely US made. Sometimes a used .25 or .30cal pops up for $1.5k+ and I've heard nothing but good stuff about the Krait AFTER it's regulator has been fixed/updated, new models will have this, or a Huma reg is always available too. The Krait L (600mm) and Krait X (700mm) both have CZ barrels, all the externally adjustable features you will find in your M3 but without the hassle of needing to tune it, as it shoots great out the box according to everyone I know with one. They are great slug guns and very well priced, without needing any upgrades.
But i think you will be happy with ANY of these quality guns, I would just decide if you are okay purely shooting off a bench/rest and size/weight isn't important to you, I'd go with the longer barrel models.