Wow - Shockwave Blade may have an issue with the how long (where) "it is fixed on the end of buffer tube"
"Take the Shockwave for example, when used with the KAK buffer tube there are 12 positions for the Shockwave blade to be affixed. That does position the Blade at a much longer length than any of the SB Tactical braces. That might be what the ATF is referring to. Same goes with the Tailhook being used on adjustable modified stock. Affixing the brace at the end of the buffer tube is not illegal. But if you do so and it results in making a super long brace then the ATF has a problem with that."
Mr Gunsngear Commented on Shockwave Blade --- "Length of Pull" Issue.If lenght of the pull of the Blade longer than 13 1/2″, them it would be a "problem" in regard AR-Pistol Configuration
13 1/2 " is considered as the standaed length of a rifle stock.