Fully automatic weapons are very difficult to buy in the US - it's restricted to 40+ year old weapons, requires a bunch of paperwork, and the local county sheriff can refuse permission.
Now, semi-automatic weapons are easy to get in the states in the US that are still mostly free - but what does that mean? A semi-automatic weapon shoots one round every time you pull the trigger. Just like most weapons that have multi-shot capability for the last couple of hundred years. The difference is, the gas escaping from the round cycles a new round into the chamber rather than you having to mechanically do it via pumping (like a shotgun or a tube-fed 22) or pulling the trigger again (like a revolver), or advancing the round with a handle, like a Remington 700. Semi-automatic weapons are old technology, dating to the turn of the 20th century. If you want to ban semi-automatics, you're basically saying you want to ban anything developed in the last century plus. Which is ok for you to advocate for, just be honest about it.
As for banning explosive devices? Are you going to ban fertilizer, used by basically everyone who has a lawn, and all farmers everywhere? Are you going to ban diesel fuel? If you can't do one of those, you can't ban explosive devices.
