I’ve shot mine a few times in competition. The 1907 is a neat gun,it’s reliable, accurate and interesting. Its time period is spot on and correct for our time frame. I will have to look up my data. With it being a blowback design with a big inertia block in the forend the rifle does not have a broad range of flexibility in the velocity department. Mine will run reliably at right around 1600 with 180 grain bullets. Factory was 1850. I’m using 12.8 2400 with the original profile lead bullet 180 gr. 

challenges for using the 1907.

brass has got to be made from something else. The experts recommend 357 maximum cut to length and turning the rim along with cutting an extractor groove. That works and works well but a lot of steps. If the extractor on a particular rifle will pull it 5.56 or 350 legend cut to length could be a viable option and if it is would save a bunch of work and money.

the bullets are specific. For mine to feed it has to be round nose and needs correct overall length. These lead bullets can be readily purchased that are correct. 
the barrel is 351 diameter. 

magazines. 5 round are normal, 10 is the cat daddy! However the original(reliable) 10 rounders are pricey, bringing more money now than the whole rifle cost a few years ago. Probably don’t need but 2 mags. Reproduction 10 rounders are available and probably way better than they were 15 years ago but I have not tried them lately. 

All in all a great rifle that handles well and is fun to compete with.