Thanks, Richmond,
Well, looks like I got them, as well as guts ...
Actually it is not that dangerous as long as the barrel is in good overall condition.
In my experience, even a thick stable layer of inside rust does not really matter, considering the enormously thick barrel walls of 16th and 17th c. muskets which have an average weight of ca. 6-9 kgs. The heaviest matchlock musket I ever handled, Suhl made, dated 1636, is in my collection. It weighs in almost 10 kgs (the barrel alone 8 kgs), it is
not a wall gun - and I fired it! Due to its enormous weight I remember the recoil was very soft.
Actually getting it ignited was not exactly easy because of the thick barrel walls; I had to fill priming powder into the touch hole until it was literally flowing over!
And: aiming a monster like that makes you understand while the old musketeers employed a rest ...
In the 1980's, the staff of the Graz armory, Styria, undertook a major project recorded both in a catalog and on VHS video, firing 200-400 year-old flintlock, wheellock and matchlock muskets, and flintlock and wheellock pistols, all from their collections. OK, it is true they had them officially proofed before, and the barrels got struck with modern proof stamps as well - which in my eyes is cruel.
m