SpudFiles

Hey all- Workin on my pneumatic rifle, and tryin to decide what to do as a gun body. it's too complex to shape out of wood so I'm going to cast a body. What I'm wondering is how durable is bondo body filler in terms of threading say a screw into it? Could it handle a screw being threaded into the same hole repeatedly (for takedown) or would that just strip out?

Don't really have to worry about its "impact" resistance since i will be covering the outside surfaces with some sort of hard plastic for protection against knocks and scratches.

Bondo usually breaks when screwed, but you can glue a bolt on the bondo body.
After it hardens, it´s kind hard to polish, but there are a good way to shape it: just before it reaches the hardest point, it´s very easy to cut, but does not stick any more, a great opportunity to give it a desired shape

I use a product called Builders Bog, not sure if it exists outside Oz. It is your basic two pack, matchbox of grey goop plus match head of red goop gives pink goop.

If you mix it right and let it cure properly you can drill it, tap it and it machines and polishes quite nicely.

Should work well for a stock / receiver type job.

So long as you pre-drill the hole and use a very low thread count screw, (wood screws are probably best) it'll be fine. You can even get the fiber-reinforced bondo for extra strength, since it only costs a couple bucks more. I've fired cast slugs into a concrete wall at 300 fps and they chip around the edges but generally hold together well.

You could use threaded inserts in your casting, that way the threads aren't directly in the bondo and the force from the repeated screwing(lol) would be distributed to the casting more. Just a thought.