I decided to go to Bullet Test Tube's web site. Here's what I found:
Are the results comparable to ordnance gelatin?
Yes, in some ways. With regard to penetration you can multiply the penetration depth in the Bullet Test Tube by 1.34 to make a relatively accurate prediction of how the bullet would have penetrated inside ordnance gelatin. However, ordnance gelatin does not offer a reliable means for measuring the wound cavity bullets create. And, ordnance gelatin offers a great visual exaggeration of the affects of what has been called the “temporary stretch cavity”.
With the Bullet Test Tube you can physically measure the volume of the “wound cavity” which is the actual material physically displaced by the penetration and expansion of the bullet thru its entire depth of travel.
That's the point I'm making.