Thought I'd add in my recent experience. I placed orders with Optics Planet, Target Sports USA, SG Ammo, and Lucky Gunner on March 5. Would have been glad to order from only one, but stock was an issue.
All have been good to me in the past. Target Sports USA was amazingly fast--just a few days to arrive. Lucky Gunner was next, great communication/updates, but shipping was a tad high. SG Ammo arrived a close third. Optics Planet package is still en route--as scheduled, it will be 12 days from order to delivery. (They did send an update saying they're backed up--so was glad they were up front about it.)
I know I could save a few cents per round (and sometimes more) by chasing the lowest prices on ammo price web crawlers. But my advice: before you do that, check reddit for seller feedback. Some of these operations are super shifty and may not be worth the aggravation in dealing with them and your credit card company afterward.