Hey Guys,I am also a owner of both of these(and more)..My newest 4 bore is a Real shoulder cannon at 26 pounds with 22" RIFLED Barrels and a true 1" hole in each barrel!This "aint your daddy's 4 bore" holds true with this custom double.Aptly named "T-Rex" by me,it shoots Jacketed 2000gr Soft Points and Solids from its rifled barrels up to 1500fps with Smokeless loads of Blue Dot Powder.This is Far More Powerful than the old ones shooting round lead balls or conicals at much lower velocitys and slower twist.The TKO factor (Taylor Knockout Formula) is 400 Plus where a .600NE is a mere 160 and a .700NE is 200!! I am getting under 2" groups at 50yds(each barrel will touch holes!).I also have a 8 Bore Tolley and a 7 bore Greener,but these shoot 1000-1250 conicals at 1200fps or so and are no match for there Big Brother!As far as penetration goes,I shot a 5/8 steel hanging plate at 20yds witha 2000 soft and it not only went through it,it broke the support steel cable suspending it!Awesome Power,I can wait th get a Cape Buff with it next month in the shoulder with the 2000 softs...I do have several videos of me shooting it now on YOUTUBE.COM under T-Rex! T-Rex II T-Rex III Also,I do have some Big Doubles For Sale .577,.600,8 bore and 7 bore.