difference between what it's like for you to squeeze the trigger each time and what it's like when the stock fire happens, the bump fire. >> great. we'll start with the semi-auto. i'm going to pull the trigger as fast as i can. so now we'll go ahead and do the bump fire. >> reporter: so you see that there. they're relatively cheap, $150 to $300. easy to find. easy to install. the most frustrating thing about these, the glaring loophole here is because every time your finger comes off of that trigger and pulls it again, they are technically legal. that is still technically a semi-automatic rifle. as we mentioned, wildly inaccurate, but if you have an extended magazine, if you have a scope, if you have a tripod, if you're set sit sitting in an elevated position looking down on thousands of people, what the