Just have to get lucky and find as many in stock at the same place. Del-ton usually stocks all the 5.56 small parts. I've had good luck with jsesurplus in the past for both platforms. Brownells has been pretty decent lately. When I need something I usually just google the crap out of it and crossreference with the other parts I need. Little trick...sometimes doing an image search will take you to vendors that don't pop up in normal searches. I've found some great deals that way. Just look at the image Web address to see if it originates at a store.