Bullet to penetrate bullet-resistant glass

[Clutch]

Personally, I'd spring for the aforementioned M4 Super 90. Unless you're going to write it in as a plot point somewhere along the line, a slight credibility issue could come up with using a fully-automatic, very distinctive looking shotgun, especially if you're planning on leaving any of the victims of the ambush alive...

"I don't know what I could tell you, man...one of them was wielding this really blocky-looking gun...I just know one thing...I ain't never seen a 12-gauge fire that fast..."

Of course, that's just me thinking. I don't know what kind of realism you're shooting for here (no pun intended).

On a tangent...I've just started on my second and third novel, and this topic has inspired me to ask a couple of questions, one for each.

1) The second novel is a direct sequel to the first, taking place some three years after the first. One of the main characters, an LAPD detective, has been established in the first novel to carry a Walther P99AS in 9mm (unrealistic, yes, but despite the fact that I pretty much went the summer-blockbuster route with the novel, I did try to allude to his getting approval to carry the gun). He also used a SIG 552 as a carbine, but lost it in a climatic gunfight. As I start the second novel, I've toyed with the idea of replacing the SIG with either a short-barreled variant of the 556 or a Colt M933 (or similar variant). Should I choose either of these two guns, or should I just have him acquire a new 552 and roll with it?

2) The third novel is more of a crime drama, set in Baltimore. I'm trying to decide on a sidearm for the main character, an assassin with a tragic past and vengance on his mind. I've floated from a Desert Eagle, quickly over to a P99 (I know, I know...but I really like the gun), to a SIG Pro, to a Beretta, back to the P99. I'm kinda stumped. Any suggestions?