I have a Ruger SP-101 that I'm wanting to finish in Norrell's flat black.  Shiny guns just don't do it for me, but I bought it years ago because 1) it was a good price, 2) you can never have too many guns, 3) even people like me who don't care much for revolvers should own a few so we keep ourselves properly grounded.

So now I have the equipment and skills to refinish it, and I'm not certain what parts I should protect from the abrasive blasting process.  Obviously the bore and chambers and the internals, but what else?  Should I protect the front & rear faces of the cylinder too?  I want to eliminate as many reflective surfaces as I can, but not at the cost of function.

On the cylinder, plug the front and rear of the chambers with rubber plugs to prevent getting any blasting inside, and don't over do the front.  Erosion of the sharp edges of the chamber should be prevented.

On most parts, a light blasting will have no adverse effects.  It's only where you use more aggressive type beads, or higher pressures on the stream.

A light blast with ordinary beads will give a nice flat gray finish.

One "watch-out":  DO NOT use a blaster that's been used to blast carbon steel on a stainless steel or aluminum.

The media will be saturated with carbon steel particles, and these particles will be embedded into stainless or aluminum.
Later, these carbon particles will rust, damaging the stainless or even the aluminum.

I've had people mystified as to how the Hell an aluminum gun part could rust.  This after they used a machine shop or automotive shop blaster that was used for ordinary steel.

The WORST possible case is the auto shop blaster that's been used to blast rusty brakes and car parts.
Shops that do aluminum and stainless have blasters JUST for those materials, and another for carbon steel.

Thanks.  I had planned to dump the media out of my blast cabinet, vacuum it out and put fresh media in.  I'm using #80 garnet (I have aluminum oxide on perpetual backorder) since I'll need more bite than glass beads can offer in order for the Molyresin to adhere.

I planned to use foam earplugs to protect the bores (2 per chamber plus 2 in the barrel).  I'll go very lightly on the ends of the cylinders.  I'm guessing the cylinder-to-chamber gap is pretty important to not disturb.

Bead blasting shouldn't affect the barrel/cylinder gap, but there's no real reason to over do it in that area.

What you want to watch is that the sharp edges of the actual chamber mouths aren't rounded or eroded.  This will ruin accuracy.

Also stay out of the forcing cone.  The outer edge of the cone is critical.