Indeed snap on forends are automatically associated with lower priced guns. However, I think I have read in some older material that the snap on has the advantage of keeping pressure on the action bar and reducing the rearward forces on the face of the action. It might be that the Evans was built with this in mind. I dunno……

Regarding lengthened chambers, I too would prefer them left original but nothing wrong with the lengthening. To err on the cautious side I’d keep my longer ammunition pressures within the new proof limits.

I would ask: what is it about the gun that the seller is saying it was made as a pigeon gun? I imagine a lot of so called pigeon guns are just heavier shotguns, perhaps made for waterfowl or mixed bags.