One of the two blasters Tobias Beckett uses in Solo
I suggest you use CA Glue to attach parts and on the inside cover the joints with extra ABS plastic and or coat the inside with resin.
Seams use either bondo or CA Paste (CA Glue mixed with baby powder)
XTC-3d by Smoothon for the clean up of print lines.
Steps of how i put parts together.
1.) Glue parts together (in sections that make logical sense)
2.) Light sanding
4.) Wet Sanding
5.) Filler Primer
6.) Repeat steps 4 and 5 until desired finish