http://www.firearmstactical.com/briefs3.htm ...
... I found the above interesting and was wondering if anybody ever tried it or thinks that it is a good idea / valid approach.... A quick and easy method to determine bullet or shotshell performance out of any handgun or shotgun is to gather several (and we mean several -- about 30) cardboard half-gallon milk cartons (plastic won't do).
Fill them full of water, line them up side-by-side three abreast, in three rows of 10 (each carton should be in contact with its neighbor). Back-up several feet and shoot a bullet from your handgun into the center row of cartons.
Count the number of water filled cartons the bullet penetrated, including the carton where the bullet came to rest. Multiply the number of cartons times 2.5 to determine penetration depth in inches. This will give you a SWAG (scientific wild-??? gauge) of how your gun/cartridge combination will perform in soft tissue (both bullet expansion and penetration).
The data obtained and averaged from three test shots should give you a fairly accurate SWAG. Remember to observe all safety rules when handling your firearm. ...