I've had good luck with TULA Small Rifle Primers ...
I wonder whether the #41's are kinda like buying "Organic" ... You Know: label it "Organic" and you can charge more?!
https://www.natchezss.com/cci-standard-primers-41-5-56mm-military.html
They are a harder primer in order to prevent slam fires in semi and full auto rifles. They are not "regular" primers, and they cost the company more to bring to market.
If you can find them for 4 cents a piece delivered, buy all you can as you will never find them cheaper.