I have a hw77 177 and just bought a hw97 in 22cal. Is it legal to put a 97 stock on a 77?

If the 97 stock ISN'T a thumbhole.... I'd think yes. I have been told and it looks like they are the same power plants just different stocks.

That being said, unless you are shooting master scores at a national or state match, doubt anyone will care.

Then Nobody would care. There are the same gun just minor differences. I would like to shoot a event next year and will have a good drive to get there. Just don't want someone to tell me I cant shoot.

If you mean the national, PM Dustin. It's his match. I don't see why it'd be a problem and honestly, if you said nothing, no one would notice or care.