Long firefight with the G-Men: Really?

Re that endless shootout near the end in which several of the gang get killed:

1) Is this one of the longest firefights in film history? Or at least the most squibs ever popped. Bloody too, with some deaths reminding me of Sonny and the Tollboth in The Godfather.

2) Were these lauded FBI agents really that amateurish? No backup, no radios, yet everyone has automatic rifles with infinite ammo? No vests or other protection? If bystanders die, too bad? I get that this happened nearly a century ago, but still. Automatic weapons are known more for overkill than precision, which is why they’re not used much in modern law enforcement.

3) No one gets a chance to surrender? Harry throws up his hand yelling “Don’t shoot!” but gets blasted anyway. Group of farmers with guns down Homer in the street. Bleeding, he pleads for a doctor but gets the circular firing squad.

And Purvis seems to enjoy shooting up a bedroom where a sleeping man and his girl offer immediately to surrender but can’t be heard over all the shots, even getting in a few extra once his man is down and near death. Not what I’d want in a top law enforcement agent with big guns and the mandate to use them. His failure to identify the suspects at the hotel alone got three innocents killed.