HW100 Picatinny rail

bandg, is your primary purpose in looking at a rail for added rigidity, or the use of Weaver style rings? I see several options for two-piece adapters, but that would do nothing for stiffening the receiver assembly. But the good news, with a low mounting magazine, your one-piece rail options are numerous. I would be inclined towards the BKL rail (part 568), just because I've had excellent results with their rings. I have one of their one-piece mounts (which includes the rings in one piece) on a spring piston rifle, and it has been rock solid. If the ring height works for you, their 4", unitized mount might offer the ultimate in a rigid setup (part 360).

I agree with your view on BKL. I haven't used those particular mounts but I've used their products on multiple rimfires and some airguns now for years-first class hardware. The primary purpose for the rail was because I have what I consider to be the best adjustable rings available on hand in Picatinny. The thought of possible "extra" strength across the receiver was a far secondary issue, noted because I've seen a couple of articles note that it might be a concern. I agree that it probably isn't due to the history of the rifle and it's performance, but I don't believe it is certain one way or the other. I do have the UTG snap in adaptors on hand and they would work fine with the factory dovetail and the pic rings I have. I was just trying to consider all options. 

As an aside, the Hammerli 850 rail noted above by Scoeri is discontinued and apparently only available from Krale at this time, based on my web search. Depending on when things arrive, I can mount the pic rings using the UTG snap in adaptors, I can use the Brittania rail, I can order the Hammerli 850 rail, or I can order dovetail rings. I'll probably mount the scope using the UTG snap in adaptors as I've used them in the past with no problems ever noted and I have them here. Since the Hammerli rail seems to be no longer readily available, I'll probably order one from Krale just to have it on hand. From all I've read here and elsewhere, I would probably section it as Scoeri suggested above and mount it as a two piece rail if I ever used it. Never can have enough hardware on hand IMO and options are always good. Now I have to get a bigger box for my "on hand" hardware. Thanks for the response.
 
To add to the long winded bit above, the thing that drew my eye initially to the Britannia rail (and later the 850 rail Scoeri discussed) was how low profile they are. I don't mind a scope a bit higher than many folks appear to like as I'm not a "cheek weld" fanatic, but adding high rings to any adaptor that also adds height can stack up relatively fast. That seemed to be an advantage for the Brittania and 850 adaptors, they seem to add very little to mounting height. The Brittania grub screw reliance is the least attractive thing about the design and I may well regret ordering that but we'll see. I'll see how snug it fits when it arrives and note it here, FWIW.