Your word choice makes that difficult to answer.
There are some extremely well-established wildcats that probably exceed the .17 WSM and .17 HM2 (and .17 Aguila) in popularity, combined. They're beyond experimental, and have well established load data and chamber dimensions - even if not recognized by SAAMI. One cannot, however, buy ammunition for them from WalMart. ...But you can't do that with .416 Rigby, either.
What do you mean by "experimental"?
Wildcats? - Like .17-223, .17 TCM, etc.
Or weird/illogical crap that will never catch on, even if it is moderately interesting? - Like .17 B&D, .17 SPC, .17-284, etc.
'Standardized', 'wildcat', and 'experimental' cartridges are not a subject as black and white as many people want to believe.
Everyone knows what the 8mm-06 is. It's even a standardized cartridge. However, the standard version of the cartridge cannot be chambered, nor can factory ammo be made for it, because the rights to the cartridge are tied up in legal disputes. A-Square owned the rights when the company folded. Now, if someone wants to run that "standard" cartridge, a modified (experimental?) version must be used.
Nearly everyone in the gun world knows what .458 SOCOM is. Nearly everyone in the gun world probably knows someone that owns a .458 SOCOM. In some parts of the country, one can even buy ammo for it at WalMart.
.458 SOCOM is not, however, a SAAMI-approved cartridge. Nor is it standardized. There WAS a standard, which Tromix, Rock River, and a couple other companies still adhere to, for reliability, safety, and licensing reasons. But PTG, Wilson, and a couple other companies tweaked the chamber dimensions, in order to avoid Teppo Jutsu's copyright on the case and chamber design, and created variants that don't always play nicely with each other (or with the original).
.458 SOCOM is not just a wildcat, but a wildcat with "wildcats of the wildcat" being the chambers found in the majority of the rifles on the market.
Yet, you won't find many people that are going to consider it an "experimental" cartridge at this point.
What would be "experimental" in the .17 caliber world...?