The test gun used by SmallBoreShooting.com for pattern testing and otherwise evaluating 12 gauge cartridges is a Baikal IJ-58 side-by-side boxlock non-ejector which belongs to the contributor known as The Hedgewalker.
The gun has fixed chokes of (nominally) half and full, having constrictions of 0.017″ and 0.041″ respectively, with 2¾” chambers and 28″ barrels. The bore sizes are tight as is typical for European / Asian guns at 0.721″ and o.717″ respectively, which makes it especially suited for use with fibre-wadded cartridges.
The test gun used by SmallBoreShooting.com for pattern testing and otherwise evaluating .410 cartridges is a Yildiz “Elegant A4″ side-by-side boxlock which belongs to the contributor known as The Hedgewalker, who blogs about his experiences with the gun in another section of this site.
The gun is a multi-choked non-ejector which makes it ideal for pattern testing cartridges across a range of choke constrictions to give a broad indication of a given cartridge’s performance. It has 28″ barrels of exactly 0.410″ bore size and 3″ chambers capable of accommodating all commercially available .410 shot shells.
The chokes available for use with the gun are marked with between one to five notches where one notch represents the greatest constriction and five notches the least. The constrictions are, in order of increasing tightness, 0.005″, 0.010″, 0.015″, 0.020″ and 0.025”.
Here’s a picture: