Interesting notes on artillery, and it makes perfect sense that the wear on cannon barrels internally would be effected over time by discharge of materials, not to mention fouling from detonated black powder. It does not seem, of course. that stones as ammunition would apply to the deterioration of shipboard cannon, but the analogy is well placed.
Here I would note however that the 'spread' (uh....scope? )of the discussion seems to have expanded a bit. I think I may be the culprit here as I included the use of 'langrage' (=sundry materials along with varied ball) as shot in cannon...……...however this was intended toward a maritime setting. What I had noted was that the heavier cannon barrels were not as susceptible to internal barrel damage by use of such diverse ammunition as would be the case with the RAIL GUNS that are the topic of the OP if such was used in them.
Bringing in the 'choke' a bit more
when I entered the discussion, despite having limited exposure to guns and artillery, I wanted to respond to Cap'n Marks note on these kinds of rail guns used aboard privateers and pirate vessels. Again, this was addressed to maritime matters as far as these guns, which led to the blunderbuss spectrum (due to flared barrels). ….and the use of 'langrage' in cannon.
While such miscellaneous material was used as shot on these pirate and privateer vessels, it does not seem (as perfectly explained by Cutlass Collector) that such use in these rail guns (or blunderbusses) would have been a good thing to do.
The discussion also addressed the purpose of the flared barrels on these blunderbuss/rail guns as being primarily for loading in adverse circumstances such as would be present in the pitching of a ships deck etc. Addressing the shot dispersion theory, again perfectly explained by Cutlass Collector dispelled the notion that a flared barrel was to 'spread' the shot more widely in discharge.
I just wanted to reiterate the elements of the discussion here, and to say again how much I appreciate these outstanding explanations on the varied aspects that have pertained.
Cerjak, thank you again for sharing this rail gun!!! Very nice piece!!!