I don't have any personal experience with MARS lower, but this doesn't sound right. I'm pretty sure it's mil spec.
I believe the issue is that the ambi bolt catch on the lower has trouble fitting into uppers that are not mil spec.
E: Somebody on Reddit said this: "Pretty much avoid everything that isn’t the FCD billet upper made for the Mars L or standard Milspec forged uppers. The bolt lock paddle hits the brass deflectors on most billet and enhanced forged uppers."
I think that's because the KAC upper is mil-spec design. Uppers where they've "enhanced" features seem to get in the way. For example, the BCM MK2 has the forward assist pushed almost all the way up to the brass deflector, and blocks the ambi bolt catch that comes on these MARS-L lowers.
I misread. I thought I read that it didn't work with Mil-spec.
Yea I just got off of the phone with Joe at LMT and it does indeed have a bolt hold/catch issue, the catch isn't getting enough up travel. It'll be going back to LMT to get repaired or replaced. It's a bummer but I am glad I caught this before selling it and it became someone else's issue and then made me look like a deadbeat seller. Should I decide to sell when it returns I'll let the interested parties know before relisting it but for now I'll have to pull the ad.
