I’ve never understood this line.
Looks to me like it means “I’m not impressed by your weaponry.”
His weaponry is superior because it’s custom-made.
Incestuous person, make people feel good! Regard! My feces is a long established tradition.
You’ve just pointed out that “custom” is one of those words that has two opposite meanings, like “sanction” or “cleave.”
He’s bragging that he tricked out his guns with rims.