A good friend and myself occasionally shoot various types of ammo in a manner that allows us to recover the bullets for examination. We have shot thru wood, glass, cardboard, and water soaked products. This was our 2nd trip with 10mm included. We were firing into water soaked reams of copier paper that were held tightly together with duct tape. Two reams stood up back to back stopped all hollow point ammo in the 2nd ream, except the .45 ammo...it was recovered in the 1st ream. The reams are very hard on bullets and certainly not meant to be compared to tests using ballistic gel. Not exactly scientific testing but enough info is gathered to form some educated conclusions....more importantly it is a lot of fun. The 9mm was shot thru a G19, the .40 thru a S&W M+P, the 10mm thru a G20SF, and the .45 ACP thru a Les Baer 1911. A note in regards to the 10mm ammo: all bullets fragmented so I gave a total recovered gr weight plus a gr weight for the largest piece recovered. 9mm 147 gr Federal LE Tactical HST: Recovered weight = 147 gr. Widest expansion point = 0.727" (This is an anomaly due to a single lead petal that stretch out in an irregular manner). (No fragmentation at all). 9mm 147 gr Speer GD: Recovered weight = 147 gr. Widest expansion point = 0.584" (I believe this expansion to be more normal for a 0.355" bullet). (No fragmentation at all). .40 S&W 180 gr HST: Recovered weight = 173.9 gr. Widest expansion point = 0.759". (Minimal fragmentation with 6.1gr. not recovered). .45 ACP 230 gr HST: Recovered weight = 229.6gr. Widest expansion point = 0.837". Extremely minimal fragmentation with 0.4 gr not recovered. (This bullet's expansion was perfect, with beautifully formed petals). 10mm 200 gr Hornady XTP (Underwood): Recovered weight = 192.3 gr (178.2 gr largest piece). Widest expansion point = 0.665". (This is the only 10mm that was fired that didn't exhibit massive fragmentation/bullet failure). 10mm 180 gr Hornady XTP (Underwood): Recovered weight = 160.0 gr (140.0 gr largest piece). Widest expansion point = 0.658". (Note: this was fired into a new, tightly packed ream of paper on our 1st trip, which probably had an effect). 10mm 180 gr Speer GD (Underwood): Recovered weight = 168.3 gr (107.4 gr largest piece). Widest expansion point = 0.638". (Complete bullet failure). 10mm 180 gr Montana Gold (Buffalo Bore): Recovered weight = 170.3 gr (119.9 gr largest piece). Widest expansion = 0.561" (Complete bullet failure with 10 fragments founded, but note that this ammo penetrated the deepest of all 10mm ammo fired). 10mm 165 gr Speer GD (Underwood): Recovered weight = 163.45 gr (109.7 gr largest piece). Widest expansion = 0.619" (Complete bullet failure). Casual conclusions: 1) The HST bullet performs incredibly well at standard pressures and normal FPS ranges for all calibers shot. (I will be loading my G19 with some of my 147 gr HST ammo from now on). 2) The 200 gr XTP in 10mm maybe the only bullet (from what we have tested) that is holding up to the "hot" 10mm loads. 3) Current design .40 caliber bullets being pushed 200-300 fps faster for 10mm loads will cause some sort of bullet failure....in many cases extreme failure. Again...the paper reams are very, very hard on the bullets. (We considered bullet failure when the copper jacket separated from the lead portion of the bullet and caused major fragmentation). Questions: 1) How would a .40 caliber HST bullet hold up in a "hot" 10mm load? 2) Is bullet fragmentation a bad thing if the penetration of the largest recovered piece is deep enough to incapacitate? (Example: The Buffalo Bore bullet left a track of sharp copper shards all the way from the 1st start of expansion all the way to the largest piece of recovered lead. This ammo fragmented the greatest out of what we have tested but penetrated the deepest. This would have been a very ugly wound in living tissue). A final side note: Underwood 10mm 180 gr FMJ zipped thru 4 reams of paper, 2 water-filled gallon jugs, and into 8" of wet sand. Nice to know if a G20 was a back up in 4 legged critter country.