The firearm I'm looking at is a MP5. 'sub-machine gun', 9mm calibre, retractable buttstock (most likely MP5 A3). Firstly,many definitions of a submachine gun are a select fire weapon that fires pistol ammo and can be used either as a semi-auto or as an automatic firearm. The MP5 generally fires in bursts, even though I have never yet come across a true full auto MP5 (they say a ratchet, is added that converts from full auto to burst). 1. Does anyone know what the BATFE, AFTE, NRA or other body says what a submachine gun is? 2. Does the MP5 come with a preset amount of cartridges that are discharged in a burst, e.g. 2,3 or 4? or can the burst vary between 2 two 4 (or even 5 rounds), when the trigger is fully depressed and held in the burst mode? 3. What needs to be adjusted/modified on the MP5, to adjust the rate of fire in the burst mode?