Just bought this one. Can it be converted into 9mm by barrel swicha ala glock 23 into 9mm?
Thanks

No, and neither can a Glock 23 be converted to 9mm by barrel switch. The two cartridges have completely different head sizes and rim dimensions, and so the breech face required for a 9mm is considerably different than a .40 S&W.

It is possible to do a barrel switch on SOME .40 caliber pistols to make them safely fire .357 SIG (SIG Sauer is one, but not Glock as Glock also requires a magazine switch).

Actually, the glock .357 sig mags and .40 cal mags are the same exact mag but with different stampings, all you need is the .357 sig barrel and either mag and you're fine; as most know, .357 sig is a .40 cal necked down to a 9mm, and size of the main body of both casings are identical, hence both mags working in either one's place. But with glocks, you have to swap the extractor if you go from 9mm to .40 or vice versa, as the extractors are different between the pistols. A friend of mine did this with his glock 23 and a conversion barrel from Lone Wolf and it worked fine. There are several companies, such as Lone Wolf, who make conversion barrels for a decent price.

I bought a used sw99 as 40 cal. does S&W still honor the warranty or does that only apply to initial owner?
Thanks in advance