a couple buddies went and got a glock 27...they guy at the store told them to just use the plastic scrubber fer the bore.
i have always used a metal scrubber.
whats the story behind the plastic scrub brush only?

I have always used the nylon brushes (on my 23 and others too). The only reason was that brass implements (jags, brushes, patch holders, etc.) reacted with the Bore Eliminator stuff I was using to clean with. The cleaning patches always came out blue green from that reaction. Didn't do that with nylon.

thats the copper/brass reacting with the metal of the bore?
i am just wondering, is it a must?(to use the "plastic" scrubber?)

not a must, i dont think it hurts anything and prob does as good a job as needed, but im sure a bronze brush or a jag would work as well

Baked - IMO a properly sized nylon brush is enough to loosen the powder fouling in the bore, then followed by wiping with a patch. Most of the solvents used today react with copper (bullet jackets) to break it down for easier cleaning. And a bronze brush will also react to the solvents as bronze is a copper/tin alloy.

I use bronze brushes with bore solvent. But I rinse them off immediately after use. They've been going strong for a couple of years now.