So I was gifted a 7 inch AR upper complete. Was not going to put a brace on it to make compliance easier. I don't want to worry about regulations. I just want to push it out against the sling and shoot the damn thing at close range at bottles and cans. Now I'm told that trigger position along length of gun can make it non-compliant and a 7-in buffer tube would break said regulations. I see Wing tactical and MCS have short buffer tubes. Do these things work? I'm not spending $350 on a bolt to put in it...... I had a lot of parts laying around, and including the stripped lower will have maybe $160 in it.....