Tobais,
I have several older Husqvarna hammer doubles, made before WW2, and ALL have measured 65 mm chambers, in both 12 and 16 bore. I also have several older, also pre-WW2, Germain 16s that have measured 67 mm chambers. What later Husqvarna doubles have for chamber lengths, I have no personal information about because I have never found one that handled as well as older top lever hammer doubles.
Per CIP regs, 67 mm ammo having proper service pressure for gun in question is considered totally OK for use in actual 65 mm chambers. I have done this for years with 16 bore Remington Game Loads,16 bore Fiocchi Game loads and Venuezalian Imperial 16X67 ammo, all having actual 67 mm hulls, even though Remington and Fiocchi are marked on hulls as 70 mm. Do some simple calculations of how much last 2 mm of modern, skived, plastic hulls will constrict forcing cone, even short, 10 mm cones -- think you will conclude that there really is no problem at all.
I have also Husqvarna hammer double made after books say Husqvarna went to 70 mm hulls, BUT, it also has 65 mm chambers. Maybe 70 mm story is only for internal hammer doubles??
Niklas
