It may be worth the bucks to invest in the Action Target (Provo, UT) flat steel spatterthebullet bullet trap. Great for pistol calibers and something like up to .30 Carbine or so.
A bullet trap for rifle calibers gets more problematical, with angled plates, etc.
IMHO, Caswell is a bit behind the times with their bullet trap stuff.
I strongly recommend the old-fashioned hand-cranked target carriers. The motor-drive systems are always breaking down, don't allow precise mid-range stopping (without added cost downrange sensor switching), and are more of a booger to work with.
Go a full 25 yards if you can, and put some baffles and foam in the tube to calm down the noise. It can be alarming!