I heard somewhere that side arms have a perk that you can't see that makes them spawn with more ammo. I really want to do the icebreaker glitch but sadly I don't have oneYou always lose ammo when you switch special weapons while alive regardless. On crimson I've just been using ice breaker and switch when I die or between rounds and the amount of ammo you get per ice breaker shot is a lot. I'll stick with that instead of the chance of getting rushed and adding time to the revive timer, but it's weird they kept sidearm ammo on spawn. Maybe it's their way of trying to get people to use them.
You're not supposed to be able to have special ammo, and switching to a shotgun/sniper after spawning with special would be a glitch, as you're not supposed to have the ammo as early as you can get itNot a glitch.