Ok, I lied... It turned out to be fairly "soon" after all.
I took it with me out to the range today, and here's the quick rundown:
Indexing: If your primer strikes are even slightly off centre, you have to be very careful about indexing (clocking) the adapter. Mine is if by a hair (and I mean a hair, just slightly off centre primer strikes on shells), which meant it wasn't striking the rim just perfect in some positions. Fortunately, it only took a couple of tries to find the right position, and once I had it, I was able to eyeball it into the correct position afterward (I took it out and replaced it a couple of times).
Chamber Fit: This thing is tight, and I mean
tight. At first, I didn't think it was going to slide all the way in, and then I gave it an extra push and realized that the rubber O rings were forming such a tight seal, that I was going to have to give it a bit of English to get it all the way in.
Once seated, it was well and truly seated. To clock it to find the right position (see above), it was impossible to just twist it while it was in place. I had to work it out, turn it a bit, and then re-insert it.
Reliability: once I figured out the clock position to get a good strike on the rim, it was 100% reliable. Every shot fired. Mind, I only tried a couple dozen shots, so that should be taken for what it is. If I ever get around to firing 1000 shots through it, I'll maybe remember to post and comment again about reliability.
Inserting a .22 round into the adapter: About as challenging as inserting a .22 into any other break action .22 - which is to say, not at all challenging.
Extraction: Even though it's only a .22, the brass will still fireform. This means that once fired, the empty .22 shell casing will have fully expanded the the chamber width. I managed to pry one of the shells out with my thumbnail, but it was difficult enough that I was dis-inclined to repeat the process - I used the tip of my pocket knife instead to pry it up just enough to "break" the seal that had formed after firing, and then did the rest of the extraction with my fingers.
Accuracy: See pic below. I shot about two dozen shells through it, mostly into the dirt to see where it was hitting. It seemed pretty close, so I tried putting some on paper. I shot an eight shot group (because that's what I had left in my pocket), and managed a 2" (roughly) group shooting off-hand at 15 yards using the bead sight. With a bit of practice, I would call this minute of squirrel or minute of pigeon at 15-25 yards. In all fairness to the adapter, I don't think my group size was indicative so much of the inherent accuracy of the adapter, so much as it was of the fact that it was getting near the end of a 4 hour session at the range, and I was getting of tired and wasn't putting a lot of effort into it.
I have an idea on how to really test the accuracy of it, but this will take some time and patience before I can try it out. Let's just say "the parts are on order" and leave it at that.
Overall Impression: Quite happy with it, actually. Yes, they're pricey. By the time you pay shipping and taxes and exchange rate etc., you're looking at about $150 CDN for the 8" rifled adapter, which is pretty stiff. Almost as expensive as the shotgun I was trying it in, in fact. But I placed it under the "buy it once, use it forever in whatever break action shotgun I want to" category (somehow, this is up to 3 twelve gauge break action for me at the moment, when you include my O/U ). There's no reason it shouldn't last near forever, and it adds a layer of versatility to my backpacker shotguns that I quite like. I can even see myself throwing the adapter and a dozen .22 shells into my pocket or pack when I take my O/U out for grouse, because why not?
Anyway, a couple of relevant pics:
The rig I was trying out:
And the group I got doing some lazy arsed off hand shooting at 15 yards (and yes, that is 8 shots, two of them figure eighted) :
