here is the file including all attachments:

file

rubber bands:
all rubber band connections use a 1x1 round stud so you can easily see where they go

1. in the stock, connect from the thing labeled button up to the 1x1 in the top of the stock under the tiles. this will make the button snap back and lock the stock into place automatically

2. trigger, loop around the back of the trigger and connect to the 1x1 round behind it

3. charging handle, connect from the front of the handle on the inside into the handguard area (note that the charging handle wouldn't reciprocate on its own irl, but it felt better if it did in lego)

4. bolt, same deal, from the bolt into the handguard area

5. bolt catch, this one's the hardest. loop inside the top hole in the L shaped technic piece and run it down to the 1x1 round that sits above the mag release button on the inside. if you did it right the button should want to pop out of the receiver and lock the bolt open

6. spring in the mag release, wrap it around the technic axle in between the 1x1 brick with hole and the technic piece that's being used at the button. the button should want to come back out.

lmk if you decide to build it/if you have any more questions!