If the lieberals and RCMP have their way there won't be any such thing as a LAR or BEOWULF magazine for much longer anyway so picking a less reliable firearm based on being able to have a few more rounds in a magazine is kinda silly. I'd rather have a firearm and magazine that was designed for the cartridge than a retrofit on a rifle that was designed for a completely different cartridge that doesn't feed well from the magazines. There is a reason an AK magazine is a banana shape, the x39 cartridge has a strong taper compared to the 223/5.56 which requires a curved magazine, we get away with running x39 in an AR magazine because we only put 5 rounds and in some cases 10 into it. There have been many reports of people having trouble feeding x39 from the XCR x39 pistol mags, some work and some don't.
Then there is the issue of opening up the boltface to accept the x39 cartridge that weakens it and leads to potential failures with lugs shearing off. It may not have happened to you yet but put enough rounds through yours and you'll likely see it.
If the price of the Mutant is too much then the next best option would be an XCR-L in x39, it uses a different bolt design that has beefier lugs and even though your back to AR pattern magazines you may get lucky and get some pistol mags that feed well.
I'd love to be able to run cheaper ammo through my AR's but in my opinion converting one of my rifles to x39 is not the answer. I bought a dedicated 22LR upper for cheap plinking and run 223 or 300BLK when I want more thump on a gong.
