I would recomend that you find some farmer or a tractor place
and talk them out of some of the used disc,or high tensile steel
like A 387or SA387 d that have about 100,000lb tensile strength
as compaired to 60.000 lb tensile of mild steel.
If you have a fab shop near by you could settle for some 516-70
plate ,still better than mild steel.
A .338 300gr SMK will shoot through a 1/2 inch mild steel plate at
600yrds so maybe it would work at 1000yrds but I would'nt count
The disc are hardened and might work if double stacked, but if you
had a good supply who cares if you shot a few holes in them,
And if you left the center hole open when you missed you could claim
the bullet went dead center. Ha Ha just kidding.
Also suspend the plate using some chain so it can give when hit.
I hope this wil help
J E CUSTOM