I've been reloading for 61 years and had a very strange occurrence today. I was setting up to reload a batch of .45 ACP - 230 grain Speer TMJ over 6.1 grains of VihtaVuori N340. I'm using a Lee Pro Auto Disk powder measure and inserted the disk with the 0.66 cc charge hole in place, which should deliver 6.1-6.2 grains of VV N340. I half-filled the hopper with powder and after 10 actuations of the measure, I mounted the measure on the powder-through-expander die. I then weighed the powder from the first charged case and could see that something was wrong; the weight was 3.2 grains. Subsequent attempts gave even smaller amounts of powder. I emptied the powder measure and removed the disk and found the charge hole clogged with powder. I poured the powder out of the disk and saw many grains of powder that appeared to be floating at the base of the charge hole in the disk. I then realized that there was a spider web across the base of the charge hole! Never seen this before. I thoroughly cleaned and dried the disk and started over. Powder measure now dispensing 6.2 grains and 50 rounds loaded. An extreme application of Murphy's Law to the reloading process.