Over the last couple of months of using my new 650XL , I've thought about making a round counter. Seen a few posts made out of cheap pedometers but the issue was always where to install the switch to trigger it, I have a creative solution thats at least is good enough for me. First I bought a pedometer at the dollar store for .99. Opening it up it was obvious were to solder the wires too, (shorting the contacts if correct will advance the count.)
I bought some cheap micro switches on Ebay for $8.00, they are sub miniature with a 4" arm.
I choose to install the switch in the chute were the round slides down after being crimped, that way only completed rounds will be counted.
I removed the chute, and about 3" up from the bottom drilled a 15/64 hole right in the middle of the chute, using needle files to square it up so the switch fit through it, then I epoxied the switch in place. There is plenty of room under the chute, and it does not interfere with anything else.
After loading a few hundred rounds it seems perfect rounds slide right down the chute and keeps and accurate count.