This is by far not my first build but this one still is giving me a few issues. I built a 5.45x39 AR initially I was having issues where none of the spam can ammo wanted to fire. I swapped out the firing pin for one designed for the 5.45x39 and it started firing some I also put in a increased power hammer spring and that has mostly eliminated ftf. The next issue I have been having is the rounds feeding, it initially was not ejecting the rounds so I put in a shorter buffer tube spring and that seems to have done the trick when there is just one round. I'm debating opening up the gas hole in the barrel but I'm a bit leery to do that since I don't want to overgas it and then have to use and adjustable gas block to fix it. So if anyone has any suggestions I would be open to them. I was going to try using a different mag to see if that would help, but I'm also still having some ftf's even with the changes. If anyone has any suggestions that I haven't thought of I'd appreciate them.

Sounds like it could be the gas port ....

Which buffer are you using? Is the gas block in the exact right spot, no blocking or partial coverage?
What size is the gas port, who made the barrel?

I was wondering about the gas port I know its lined up I've taken it off a few times to check and measured and its right where it should be. The buffer is a standard weight buffer. I forget who exactly made the barrel, I found him when it was almost impossible to find. I'll have to check to see what the gas tube hole size is.

Not sure if this will help but this happened to me. I did a conversion from a 20 inch hbar colt to and approved sbr with an 11.5 inch colt barrel and had feeding problems after 1 round was fired. Turned out the little rubber donut inside the bolt had to be replaced due to the gas changes going from the hbar to the 11.5 even though everything was factory colt.

Thanks for the input I swapped to a different mag style and opened the gas hole to .078 and its running well i did 5 rounds through a mag twice without a single issue. I do seem to be having some gas leaking around the gas block so I will probably change that out as well. I did not want to over gas the rifle but it would appear that was just what it needed.