I'm not sure what Wildcatter's requirements might be for his commercial tests, but a method that seems to have a lot going for it is the "Bullet Test Tube". Some details are here:
http://www.thebullettesttube.com/.
As I understand it, the medium inside the tube isn't particularly temperature sensitive, and it can be used repeatedly. For us amateurs, it's better than wet newspaper because it shows clearly the cavity the bullet makes on impact.
It got a lot of favorable press when it first appeared, and was included in several of the chapters in a pretty good book,
Rifle Bullets for the Hunter. The book was written by several current gun writers with good reputations. Here are a couple of links that describe the book:
http://brycetowsley.com/Products/product1.htmhttp://riflesandrecipes.com/html/rifle_bullets_for_the_hunter.htmlThese guys also sell it, although Barsness (riflesandrecipes.com) is currently out of copies. Amazon.com has it listed also, but Amazon is more expensive than at these two sites.
--Bob