Brechtler, Hillinger and Hartmann
"Brechtler Büxenmeister / und Hillinger Güesser / haben zwar die diametros der Kugeln gleicher Schwäre (auff die 3 oder 4 Schießlötige zeuge) gesetzt / sie haben aber auch zu den gleichen lengen der diametrorum gegen einander über bygesetzt / wievil jeder zeug (einer solchen Kugel groß) wege. Und achte ich / deß Brechtlers angab werde auß Georgio Hartman Mathematico genommen sein / der umb das Jar 1540 den Maßstab auff die Büxen erstlich (wie Hulsius fürgibt) erfunden."
Kepler. Außzug auß der Vralten Messe Kunst Archimedis. p.109.
Master gunsmith Brechtler / and caster Hillinger / have given the diametros of equally heavy balls (for 3 or 4 gunnery concerning stuff) / but to the same lengths of the diametorum they have also juxtaposed / how much each stuff (of such a sized ball) weighs. And I noted / that Brechtlers data would have been taken from Georgio Hartman Mathematico / who invented around 1540 for the first time (as Hulsius claims) the gauge for the guns.
Brechtel, Franz Joachim
The Hilliger family
The Hilliger family from Freiberg in Saxony was from the 15. century casting bells and pieces of artillery. Especially Martin I (1484-1544), Wolfgang (1511-1576) and Martin II (1538-1601) were active and well known casting for artillery.
See:
Pohl, Horst. Hilliger In: Neue Deutsche Biographie, Bd. 9. Berlin 1972.
Hartmann, Georg
Georg Hartmann lived in Nuremberg where he got a position as vicar at the Sebaldus church, he was also a mathematician and instrument maker, he is mostly known for his sundials and astrolabes.
The earliest claim, that Hartmann was the first to invent a gauging rod for gunnery can be found in Hulsius in his Tractatus Secundus, 1605, p.3. Others claiming Hartmann having invented the gunners gauging rod are: Doppelmayer, Beckmann and Fibiger who thinks, that Hartmann may have met Tartaglia at his time in Italy, and he might have told him his idea for a gunners gauging rod.
Wißner, Adolf. Hartmann In: Neue Deutsche Biographie, Bd. 7. Berlin 1966.