I was going to suggest going to your nearest welding shop or scrap yard.
And get you 3 quarter inch steel plat 4feet by 4 feet make a stand out of 4x4 wood posts make the.
When you put the steel plate on stand put on 45 degree angle.
And to prevent bouncing bullets
Put a 6inch layer of cardboard on steel plate. That mite be a cheaper rout but of course it depends on how many times you test fire.
That too!! Was not sure if their set up to roll their own blanks BTW if the caliber is large enough & weapon center use a pencil eraser end down muzzle to test triggers , will put them into the ceiling , ask me how I know that. Rofl