The GM in my area (central NY) is also closing. I used to buy ammo there when you could get a box of 525 22LR for 14 bucks either on sale or a mail in rebate. Most of their regular prices were high, much higher than a local outfitter.
There is now a Runnings about 15 miles away and they have good sales, but their regular prices for ammo is still high IMO.
As far as rifles and pistols, the local gun shops offer the best prices and best service. They dont have sales that often but their everyday prices are hard to beat.
We did get a Bass Pro a few years back but their regular prices for ammo were higher than GM. Rifles and pistols about the same. Picked up some 22LR and 9MM on sale last black Friday.
There is a Cabelas in Portland ME. I will try to visit that store the next time I go to visit my grandkids. As far as online, I am SOL here in NY. I can get my son-in-law to get it for me in ME but I will have to wait for my next visit to pick it up. At least I still have some options since they are only about 6.5 hours away.
Forgot to mention, our local outfitter,outdoor store recently had a centerfire pistol ammo sale, 40%off. Picked up some 9mm for 10$/50rd a box. 22LR was 10% off but their selection was limited to that 10c a round ELEY stuff. No bulk either in the 300 or 500 round boxes. In fact, I have yet to see the 525 Federal, 333 Winchester, or 525 Remington anywhere in the past 3 years. Some stores list it on their websites, but it is always out of stock. Is it not made any more?