Built a spent primer tube since at least 10% of my 650's primers don't stay in the cup. I have an old style 650 so the commercial tube solution was not available.
Parts from Home Depot:
Barb adapter
Tube
Cap screws
Throw away the female garden hose adapter and washer and keep the barb. Use the edge of a file to notch the barb under the flange so it fits between the "fingers" of the bracket that hold the spent primer cup (the fingers that straddle where the spent primer comes out of the press, not the fingers that hold the cup). Replace the bracket screws with the cap screws. Feed the tube into a wastebasket. The hose slides freely through a large cup hook to keep it away from moving parts.
Works like a dream!
O2