You made me remember that I had cut out a piece of 3/8" plate steel to weigh 2 pounds. I drilled a hole in it and tied monofilament to it with a loop on the end. Rifle butt down on the table, muzzle toward the sky, loop around the trigger I raised the rifle until the weight made the trigger fire. Clear action of course.
I had forgotten that I had that piece of plate cut just so-so. I remember using my paint pen and labeling it "2 pounds". I think I know where it is, I'll look tomorrow.
If you're interested in a certain weight, and have some plate steel, I can tell you how thick each thickness of steel should weigh per square foot, then we'll have to convert that to square inches to get "the" right size.
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