Building the Canadian Semi-Auto STEN

[tiriaq]

Air pressure is a variable with any medium.
Glass beads can produce a fine peined surface which gives a really fine slightly matte blue, not unlike rust bluing.
Sand, aluminum oxide, silicon carbide, glass grit, etc. will all tend to cut more aggressively, once again depending on air pressure. For Parking or coating, a bit more tooth is desirable. If a firearm is somewhat pitted, an aggressive medium at higher pressure will tend to blend the miseries in together, and when finished, the efect is not bad.
Be careful with sand. Depending on the type and source, free silica dust is a possibility, and you do not want to inhale that. A cabinet can be given negative pressure with a vacuum, and this will greatly reduce exposure.