Transformers gun with interchangeable barrels

Yet another "transformers" gun. These robot vehicles/action figures feature hands and body mounts comprising 5mm holes, into which 5mm pegs on accessories are a push fit. This gun was inspired partly by the "nose gun" found elsewhere on Thingiverse. Updated by separating into barrel and gun body, I have in mind to add various optional barrels at some point.

The threaded end of the barrel has a narrow hole - was going to have the inner barrel pass right through but I figured it needed more area to stay stuck to the bed while printing. Left a small pilot hole so it can be drilled out after printing if required. The barrel is 5mm internal diameter. The 5mm peg hole in the back of the handle is 5.05mm diameter I think - just a shade oversized which, in my printer, after shrinkage, is a good fit on the transformers pegs.

The thread has a 1mm pitch and is around 8mm but it's not an ISO metric thread, just a custom thread - I'll add the exact dimensions to the description at some point