Good question. You want "informal". To some that would translate to a chunk gun or light bench rifle. I'll show mine again if I can get this new software to allow posting of pics. It has not worked recently.
Here goes:
BTW, in case it doesn't work, the upper rifle is my light bench, X-sticks target rifle. And, before health issues made me too weak to lift it, was my offhand range gun. It is a regular TC 'hawken' fitted with a Douglas premium barrel and Redfield Olympic sights. Very accurate. The lower one is a similar version on a TC Seneca stock.
Couldn't post pic even though it is one I have used here before.