I dont get it... are you saying you're shocked that they do the same damage, or are not trusting a statement that they both do the same damage?
I think he's a Gunner who got owned in a 1on1 against an Assault. It happened to me too and I was surprised at first but once you get that double minigun it's all over lol.
If you catch a Gunner from 'cold' (no spin-up) it's easy to get them as Assault if you're clever. If they've been firing for a while though it's best to run because the ROF tears you up real quick. The movement speed of Assault is a bonus too if you can get behind them and stay behind them. I wouldn't say that it's a major issue. I've probably been killed by a Gunner one on one as many times as I've killed them. If Assault's weapon wasn't as powerful as it is there'd be no reason to take the class, you'd be better off running Gunner in almost every situation.
An assault up close is deadly, but their rifle drops in damage rather quickly over range, just need to keep on moving.
The assault rifle does little to no damage at medium to long range, while the minigun is still powerful and accurate. Even at close range in a completely even fight, the minigun is still stronger.
Idk, I've never lost to a Gunner as an Assault, unless it was one of the Halo/WoW players who jump while they play.