Since some readers continue to dismiss my reasoning about Blakely being the originator of the so-called "Preston" shells, let's come at the question from another direction than just the Blakely patents. Here is my reasoning.
Blakely patented a unique type of "sawtooth" rifling, with the intention of using it in his rifled cannons for firing his Hex-Flanged projectiles (which some people still insist is a "Preston" shell.) Very importantly, with the single exception of a non-dug 8-incher of unknown provenance, those Hex-Flanged shells exist only in 3.5" and 4"-calibers. The following information regarding those two calibers of Blakely Rifles and their flanged-projectile rifling is from the book by Hazlett, Olmstead, and Parks, titled "Field Artillery Weapons of the Civil War".
Page 203, the 3.5" Blakely Type 4 Rifle:
"Rifling was changed from seven conventional flat grooves of right-hand twist for Type 6 to six sawtooth or flanged projectile grooves for type 4.
Page 205, the 4" Blakely Rifle:
"Recoveries at Fort Branch, North Carolina include a number of Blakely shells with six spiral flanges to engage the grooves of rifling. Ash Harrison has determined that these shells still fit the bore of the 4-inch Blakely Rifle also recovered from the Roanoke River [at Fort Branch] after more than a century of submersion. Thus it is now apparent that the type 7 Blakely rifling pattern is not sawtooth, but of the preguided [a.k.a. "shunt"] principle. On their guiding sides the grooves curve sharply to rotate the projectile with minimum wedging. On the trailing side the grooves curve gently to provide space for the supporting buttress portion of each flange on the projectile."
(End of my quoting from the Hazlett, Olmstead, & Parks book.)
Please note that Hazlett, Olmstead, & Parks, for reasons which are obvious in the quoted text, specifically identify those Hex-Flanged shells as Blakely shells. Furthermore, they did so in 1988, so those astute gentlemen cannot be merely relying on my 1993 books naming of the Hex-Flanged shells as being Blakely's design.
In his book titled "Civil War Heavy Explosive Ordnance," Jack Bell says:
"Two other projectile designs -- both flanged -- were used in Blakely rifles that used the shunt system. Both are actually Blakely designs ..."
We know for certain that the Hex-Flanged shell in the famous 1865 Charleston SC photo were labeled by the yankee photographer, not the Confederates. Where did he get the name "Preston" for it? Logic suggest she found the name on the shipping-crate from its manufacturer ...which was the Fawcett, Preston Co. of Liverpool England, the manufacturer of Blakely's cannon-designs and projectile-designs.
Which of the following two scenarios do you readers think is more likely to be the correct one?
Scenario 1: Blakely himself designed the Hex-Flanged flanged projectile for use in his six-groove "sawtooth" pre-guiding/shunt rifled cannons.
Scenario 2: Some unknown engineer at Fawcett, Preston & Co. designed the Hex-Flanged projectile for use in Blakely's cannons.
While you are thinking that over, please note that the HO&P book's "known survivors" of Blakely's sawtooth pre-guided/shunt rifling system cannons are marked 1862, which is one year before his British Patent application for the rifling. My point is that (just as happened in America), in some cases cannons and projectiles got manufactured a significant amount of time before a Patent for them was issued.
Regards,
Pete
