Let's see, at roughly $300 per thousand rounds that's $0.30 apiece. Assuming he had a full 20 rounds in the magazine and it took about two seconds to empty, that's $6.00 in two seconds or $180 per minute. Awesome. If Uncle Sam was still paying for it that would be fun.
Short story... I know the guy who started the latest bump fire craze (poor man's machine gun). He can do it on almost any rifle and has just about perfected it. He actually can shoulder the weapon and do it. There was a bunch of talk about legality etc. He wrote the ATF, and on official letterhead it says it is not illegal. That was several months ago, unless someting has changed since. Go out, practice, have fun! ;D
well i have a Akins accelerator worked great till the atf took away my spring :'( so now i have to shoot the max-11 9mm FA and am waiting on my lage max 10 45 FA upper for the mac 10 ;D so since they took away the cheep 22 from me it cost a lot more to bump fire. Now if the xcr was single stage it would be no problem to bump i get controlled 3-6 round bursts out of my m4 spr regularly