You're going to have to isolate variables one at a time. Start with good quality factory ammo. As noted above, check the chambers. If the cartridges drop freely, move on to ensuring the gas block and gas port are correctly aligned. Troubleshoot with the known-to-work lower. Make sure it has a standard buffer and a standard, good quality buffer spring. Borrow a bolt and a magazine that are known to work. Report back. For the barrel that won't eject at all, you can hand feed the round until it ejects.
Check the lowers' function on uppers known to work. If everything, checks out, and they still won't cycle, consider buying some good headspace gauges, if you can find them.
While it won't help you now, this kind of stuff is why I only use good quality parts anymore. Low end parts are a false economy, in my opinion. I've been where you are, and I avoid it now.
Check the lowers' function on uppers known to work. If everything, checks out, and they still won't cycle, consider buying some good headspace gauges, if you can find them.
While it won't help you now, this kind of stuff is why I only use good quality parts anymore. Low end parts are a false economy, in my opinion. I've been where you are, and I avoid it now.