Two Model 97 riot guns with the lug ground off?

[Blockhead]

To answer your first question, I think the only difference is between military and commercial. The LE guns would fall under the commercially manufactured category, unless it was a milsurp gun of course.

Those ARE the three grooves. You don't have a handguard on your shotguns, not sure why you need instructions on how to remove it.

Ok, so what do the three grooves signify?

And sorry if "handguard" is the wrong nomenclature. What I meant to say it how do you remove the wood-grainy ribbed thingy the slides back and forth on the boomstick.