Huge sales & process times....
The US shooting sports(firearms) industry is going thru a huge upswing now & there are record sales. Many common items like spare magazines or ammunition are low or sold out on firearm/product websites.
Gun owners or new buyers need to wait & learn to accept these factors.
I've learned over the years that the shooting sports industry & the stores-companies are time not customer service based. The ammunition & firearms companies don't produce a lot of items & won't hire more staff/enlarge to meet the demands. If a shop or gun range doesn't have a product or item, they tell you to leave. It's not like TVs or cars or cell phones. Firearms & ammunition have legal requirements & restrictions put on them.
It's a annoying & hard to deal with but that's what it is today.