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cardboard box with notch at both ends to cradle rifle works...LOL
so does a G or sash cramp with a little forethought.

I would argue its just as easy if not EASIER to do it with a break open rifle. that black n decker workmate comes in real handy to do it..... with rifle broken open you have access to look through...

bit hard on the longue furniture all the same...

and taunting the cat.....

one of the black n decker workmate benches make this a doddle to do...you can clamp the rifle in place look through bore and move Xhairs..... AND if yo utake it to range...fire your 2 or 3 shots......

bore sighter...a thing you poke on muzzle end that gives you a grid when look through scope....