bryan wrote:
Can I use an air-actuated framing nailer gun to nail parallel 2x4s
together?

I have a home business, and one of the tasks is to screw 2x4s together
to make one thick post. I spread glue on the 3.5" wide faces, then
clamp them together before fastening.

Instead of driving deck screws for fastening, I am curious if I can
use a pneumatic framing nailer.

Would I split the wood?

No need to use screws of nails. If you're gluing them together you
could use tape, string, or old bicycle inner tubes as big rubber
bands to hold them together while the glue sets up.

R