Peter that isn't a totally accurate statement. We receive new stock everyday; perhaps the rifles and lowers you wanted are/were sold out, but we still have a good amount of stock on a wide variety of items. If you are in the right place at the right time, or have stock notifications on certain items, you'll get what you want.
You are right, at certain points throughout the day, we do show items sold out, or have not yet gotten to the new inventory yet. It's still possible to get some great items, even ones which other people really want, you've just got to be watching.