I'm not quite as impressed by the penetration as some here which is not to say that this is not an excellent bullet. I studied the 6.5 Carcano military fmg years ago. My system was also wet newsprint but was only the dimension of a folded out newspaper. The Carcano bullet is quite long, extends out of the case some distance and 'looks' unstable. Most bullets defected out of my narrow, stacked newspaper but I did recover one bullet. I think it is a 130 grain fmg, of the exact type used to kill JFK. It penetrated 72 inches.
Years ago, Barnes produced a copper alloy solid that was an excellent bullet. Then Congress declared them 'cop killers'. Barnes stopped producing them. I was told that, to comply with Federal guidelines, a 'solid' bullet must be full metal jacket, meaning [I think] that it must have a soft metal core [lead] but be coated with a steel jacket. I believe the steel jacket can't completely cover the lead core--some lead must be exposed at the base of the bullet. [Interestingly, this is why the Connally 'pristine' bullet isn't pristine. It tumbled on entry, the base of the bullet striking something hard, probably bone. It struck with enough force that lead extruded from the base and stuck in the tissues around Connally's femur, which was visualized by x-ray. The bullet was by no means 'pristine'. We see photos of the bullet from one angle but, if you turn it 90 degrees, the base of the bullet is compressed 50%, and lead bulges from the opening at the base of the bullet.]
The Feds also have limits as to how thick the steel jacket must be. I'm guessing that there are different steel thickness limits for solid bullets of various calibers, but that's a guess. If I can recall rightly, Woodleigh came up with a solid that was somewhat different than U.S. Federal standards. I've heard it is an excellent bullet but available only in larger calibers.
Now Swift has come up with a new solid. Producing a better solid is no particular trick, but producing a superior solid that meets present Federal limitations, is. How is Swift's bullet designed? Does it have a lead core or a core composed of some other alloy? Is the metal of the core exposed at the base? How thick is the steel jacket? Is the jacket made of steel or some other alloy? How thick?