Your threaded barrel makes the handgun an Assault Weapon. Your large capacity magazines have NO exemption in the law, even in parts (as of 1-1-14). There can be a competition exemption for a non resident for the assault weapon, but not the magazines. Is it worth the risk for a few possible felonies? Up to you.
Telling someone they will have no problems if they are nice isn't true. You can't account for every situation. What if you get in a car accident? Get pulled over for a mistaken identity?
Permanently attached means pinned and welded or silver soldered. Loctite will not cut it.