Yes it is, and anyone that tells you they have a production mod thats brass and then plated over top needs to take a file and show me some brass shavings. No one is going through the expense of making a mod out of brass and then covering it up.
Trust me.
The v1 was standard low carbon steel then electroplated nickel which will weigh almost exactly the same as the v2 made out of 300 series stainless steel.
The only time a mod made out of stainless is going to feel noticeably heavier is if your comparing it to aluminum or titanium.