VIctor,
The cutt out on the Mark I is the ejection port for the rifle when the device is attached. Mark Is als had a different trigger mechanism , but after the Pedersen project was cancealed and the devices destroyed the guns had the different trigger parts replaced with standard ones.
The cartridge for the Device was appearently the basis for the cartridge the French later used in their 1935 series A and S pistols and an odd SMG only the French used I want to say MAS 26 but might be wrong on the designation.
It might be fun to get one of the shell shrinkers on the market to shoot .32 ACP pistol ammo through the 1903 MkI to get some idea of what the Pedersen might have been capable of.I use one on occassion in a .308 hunting rifle and find Winchester Silver Tip HP to be the most accurate at 25 meters and would expect a .30-06 / .32 ACP adaptor to work much the same as my .308 / .32ACP. Currently their are some folks offering an adaptor that supopodedly allows the use of .32 H&R magnum and shorter cases versions down to the .32 S&W (short, some folks insit on calling) AND the .32 ACP cartridge as well. No idea how accurate this one size fits all would be compared to a purpose built for one caliber adaptor but seems intersting
Enjoy your rifle and look out for folks that always know someone that has a Pedersen in their garage but can mysteriously never seem to find it. You are likely to now hear a few such claims followed by such excuses on a regular bases.
Oh and just for giggles, some of the early trials indicated that the Army had visions of using the .32 Pederesen out to 600 yards!
-kBob