I use them often. Browsing the site sucks because items aren't categorized very well and filtering options are pretty sparse. Searching by part number is most efficient. They probably lose a lot of sales simply because people can't find something.
I like to browse by brand, but its even hard to find a way to do that on the site, so I use this link
https://www.bigdaddyunlimited.com/brands/
They drop ship most items from RSR and a couple of other distributors. FYI, a lot of gun stores drop ship from RSR out of Texas.
The pricing on the bulk of their parts is the best you will find on the internet though.