A House Democrat plans to introduce a bill that would hit AR-15's with a 1,000% tax -- and

[Zeitghost]

177. Rate of Fire

Existing regulations on machine guns (burst/full auto) are not based on rate of fire. They are based on mechanical function, if more than one bullet is fired by a single manipulation of the trigger, it's a machine gun.

Rate of fire is tricky and is dependent on all sorts of factors many of which are not related to the design of the firearm. Things like the skill of the shooter, cleanliness of the gun, how much and what type of lubricant is being used, what ammo you're using, how the gun is tuned with spring rates and gas block port sizing and a host of other factors all play a part. To put it mildly, it's complicated and would be very difficult to build into legislation.