Yes, if the round has proppery been brought into battery, the firearm holds the ability to discharge without the magazine in place.
The M11 is the Sig Sauer P228, for which a 13 round magazine is standard. It can also accept 15 or 20 round magazines common to the Sig Sauer P226.
10 rounds
Best left to a trained professional
No, they are two very different models in terms of magazine size.
Best left to a trained armorer
Best left to a gunsmith or SIG trained armorer
12-20 rounds depending on caliber and magazine.
Yes, as long as it is made specifically for the P229/P228.
Try gun shows, gun shops, Brownell's, e-gunparts.com
Sig Sauer P229 and P239 chambered in .40 S&W. Here's the press release from Sig.
Sig Sauer is the Manufacturers and distributors of ''SIG SAUER'' handguns, Blaser, Sauer and Mauser rifles.
Without a detailed description of all markings, it is impossible to answer.