[Filthyfrankster]

Along with the idea of being able to two-hand firearms, we come to a certain thing that has been in use.
http://neus-projects.net/viewtopic.php?f=7&t=4299

One handing normally large/heavy recoil weapons like shotguns or sniper rifles with ease.
Normally, They would be a tad too large to properly aim, especially with one hand.

If you're using a certain firearm such as any rifle, shotgun or even the jackhammer. You will suffer a hit penalty of around -50 hit due to your shoddy stabilizing.

Handguns such as the normal peashooter or the quickdraw are fine, thanks to akimbo and all.
If you do decide to wield any of the large weapons with the two-handed grip of it, you'll ignore the hit penalty.