I recently started on a quest to turn all my stores of lead into bullets. Last week I cast over 15K of various bullets including several thousand hollow points. Since I tumble powder coat several hundred bullets at a time that works great, except you can't tumble coat HP's. Well I guess that is not completely true, Yes, you can do it, but the PC fills the HP so it doesn't expand properly.
To PC HP's, years ago I drilled a small sheetmetal plate and tack welded in some hardened carpet tack strip nails to hold and spray PC just HP's. This has worked quite well, except for heat distortion of the sheetmetal, but it just didn't hold enough bullets to PC several thousand HP's with any efficiency. So this weekend I made a new "Bed of Nails" starting with a 1/2 sheet aluminum baker's pan. I use these pans in my converted PID 30" wall oven.
I chose to use aluminum because drilling 408 nail holes for the bullets in steel plate is a lot more effort & time consuming. I set the 3/4" hardened nails into the holes and spray PC the bottom of the pan to set the nails in place; I use the mixed powder sweepings for non-critical projects like this. Then I riveted (3/16"x1/8") a sheetmetal plate to the bottom of the pan to cover the nails and keep them from ever popping out. A light touch with a grinder knocks the sharp point of the nails if you desire.
I made my first PC run yesterday. I pressed down a sheet of parchment paper over the nails with shop towel so as to keep as much spray as possible off the inside of the pan. I found a layer of paper also seems to direct the spray to the bullets making the spray operation more efficient. To place the bullets I have found I can pick up a bullet with my self closing tweezers and set the HP down on the nail point faster than using my fingers, but that may just be me. A slight downward push and the bullet is seated.
Our humidity has been running quite high and I wanted a good PC, so I set the tray in the oven and gave it a high preheat. Once out of the oven the hot tray went into my DIY spray booth and on my metal lazy Susan, which allows me to spray easily and fast access all sides of the tray.
Once cooled, removal of the bullets is quickly done by putting an empty tray on top, inverting both trays and tapping the bottom. I usually leave the parchment paper in place for another batch, but removing old parchment is quick and easy with a wire brush and vacuum.
What you see in the photos is the end result. Note: no powder build up in the HP.