KABAR2, It is a bunch of very precise milling to reveal those trunnions, rimbases and rear sight mass which are hiding within that 'trunnion ring'. Mike has 7 full pages of Excell X-Y-Z coordinates to go by when he does that 'nail biting' work. While I turn the various cylinders and tapers and external radii on that type tube, I leave the 'Trunnion Expose' to Mike who is the expert machinist in our little company.
Neither Mike nor I play the game of chess, but we do plan out 'moves' or machining operations 9 or 10 steps ahead of the first chip being produced, even on the first prototype. The high material cost for the 'rounds' of 4150 Crucible steel, $300 for the Parrott tube and $500 for the Brooke, force you to pay strict attention to what the heck you are doing!!
Double D, These Rifled Cannon Blanks we are talking about will be available as straight cylinders, saving the customer 30 to 100 dollars per customer request. Straight cylinder will be standard shape, with stepped as an option. I wouldn't worry too much about the so-called, 'expansion' of the bore in the muzzle area. This is simply theoretical stuff here, no one, but no one has any data to back this up. If there is any, it's probably located in one of the 20,000 crates in that warehouse where the govt. stored the 'Arc' in that Indiana Jones tale. What you should be worried about is the fact that a portion of the rifling in every rifled tube is irregular in the muzzle area due to the rifling head being unsupported, either wholly or partially, as it emerges from the tube during every stroke. Not everyone trims a portion of the tube off to eliminate this imperfect section. WE DO! More importantly, we will continue to remove the last two inches from each and every Blank or rifled liner that we will be making, allowing us to ship the most perfect rifling we possibly can, throughout the Entire Bore, to each and every customer.
Mike and Tracy