The inside of every A5 is rough from overspray. That is why we polish the internals. Mainly where the front and rear bolts move. That way they move more efficiently. It would be like pushing your car with the emergency brake partially set. When you polish the receiver halves it is like releasing the brake and everything can move smoothly. We all have diffent ways to accomplish the polish the internals. Mainly what supplies we readily have available.

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"A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort." - Herm Albright