I've seen polishing the A5 internals increase the velocity up to 10fps under the same settings. By removing the factory overspray on the receiver halves the theory is to improve marker efficiency by reducing drag on the A5 internals. One thing you need to keep in mind is that all you want to do is remove the overspray and polish the receiver halves without removing any metal and changing the internal diameter. Do at your own risk.

That said, here are the items I use to polish the internals of the A5.
Brasso Polish, Paint stripper, 00 steel wool, and a small plastic brush (purchased at my local hardware store). A clean wrag and some paper towel are needed as well.



The first thing I do is clean the receiver halves to remove any oil and dirt.



After the parts are dry, I apply a thin coat of paint remover. Remember to be careful not to get this anywhere but where you want the overspray removed from, I also recommend doing this in a well ventilated area.



I then let the parts sit a few minutes to allow the paint remover to work. You don't need to let it sit very long as the steel wool will to the real work.

After about 5 - 10 minutes I wipe the paint remover off carefully with paper towel.


As you can see it got most of the large areas of spray off. I'm now ready to use the polish and steel wool to completly remove the rest of the overspray and to lightly polish the inside of the receiver halves.



I apply the polish directly on the steel wool.



And carefully rub the surface until it just starts to shine under the polish. Again be carefull not to remove too much matierial from the receiver halves.

When I'm satisfied, I put the receiver halves in the sink and wash the polish residue off.



Notice that the inside surface shows mold marks and isn't purfectly smooth. You don't need to take it down any further than this.



Done. The internals are nice and shiny. I add some java oil and reassemble my marker.

i did this with very little trouble at all. this gun is very easy to dissassemble and leaves very little room for error. many people may be intimidated by dissassembling their A-5, and shouldnt be. i didnt use the paint stripper it didnt seem nessesary, just took the scrubbing pad and some simple green, scrubbed off the overspray and rinsed, i polished using 1000-2000 grit sanding paper rinsed again thoroughly and let dry before applying lubricants and reassembling. its that easy, i spent approximately 1-2 hours doing this.