What nails does the Metabo NR83A5M take?

It takes 2-inch to 3-1/4-inch framing nails up to 0.131 inch in diameter, in paper-tape or wire-weld collation. The 64-nail magazine suits stick framing and sheathing.

No. It is a pneumatic tool that runs on compressed air, so you need a compressor and hose. That keeps the tool simple and light on electronics but limits where you can use it.

How does it compare with the older Hitachi NR83A?

It is the Metabo-branded continuation of the same proven design, so the feel and reliability carry over. Check the specific model for trigger and feature differences before upgrading.

Can it fire bump mode?

This model uses a standard sequential trigger and does not offer a bump-fire or selective trigger. If rapid production nailing matters, look at a nailer with those modes.

What compressor does it need?

It needs enough airflow to keep up with repeated framing shots, so a small trim compressor will struggle. A contractor-grade compressor with a larger tank is the better match.