Anybody else find this hilarious?
I do but...\/
Yes but I was trying to stay "on the High Road" rather than calling it out.
...but it seems that the OP seems to be a reasonably good-natured feller, so yeah it got a chuckle.
Is the S&W M&P15-22 an interchangeable platform like the the AR or is the MP just an AR look alike? Also, is this weapon a centerfire or rimfire? How do the different ammo compare in price? I also noticed on the SW website that there is a CA complient model, is the magazine capacity the only difference between these two models?
First I must admit that I don't own one (though I have shot one and it was a pretty decent plinker), I do however know a bit about them so we'll give this a go anyway. It is an AR "look-alike" chambered for .22 Long Rifle, and it isn't possible to convert it to any other chambering that I'm aware of (perhaps the .17HM2, which is a rimfire, but I doubt it), though the controls are identical to a centerfire AR. The CA compliant model definitely has only 10rnd capacity, and no muzzle device (flash suppressor), but I believe it also has a "bullet button" (requires a "tool" to remove the magazine), and may not come with a collapsible stock (not sure about this one as I live in the relatively free state of NC). If I'm not mistaken all have the darn magazine cutoff (won't fire without a magazine inserted), but that isn't a horribly big deal (I've lived with it on my GSG-5 thus far). If you reside in California, you may want to strike this one off the list, as it looses a few of the attractive features in the CA-legal variant.
Now for the more difficult question...ammo (which is a valid question for any .22LR). Ammo ranges in price from as low as about $1.50/50rnd. box for cheap plinking ammo (which is great ammo to start with, but try several to see what your rifle digests/shoots best) up to about $35.00/box for Olympic grade match (which you just don't need...at least right now). I strongly recommend starting with something like Federal Champion (cheapest reasonably accurate bulk ammo I have found), Winchester 333/555 (which functions well and is cheap and fairly easy to find), and/or Federal 525rnd. Value Pack (which is about on par with the Winchester). The work your way up to a lesser cost match like Aguila Match Rifle (which is very accurate for the price), and later on to something even better like RWS Match Rifle, SK Match, Wolf Match, and/or various Eley & Lapua products.
I strongly suggest that when you purchase your .22 you find a model that shoots shorts,longs,and long rifle ammo.
While I love my little Remington Model 12 pump and Stevens 87D, both will shoot just about anything (with the action locked, in the case of the Savage), it isn't exactly my go-to rimfire...not by a long shot. It's handy to be able to shoot .22 Shorts, and those dandy Super Colibris, but by no means necessary (nor is it available in most semis, or, for the most part, any lesser priced rifles at all). FWIW, I'm pretty sure that the Henry will not operate reliably with Shorts and Longs. I would first concentrate on a decent, reliable, accurate rifle WITH IRON SIGHTS (good ones, or at least something with aftermarket options).