LRBHO Failure - Stumped

[montana]

Pull the charging handle back and measure how far back the bolt goes in the receiver that works. Do the same on the receiver that won't work and see if there is a difference. If there is , pull the recoil springs and see if their is a difference in their length. Receiver tubes do not always have the same internal length, which is why I use Viltor mil spec receiver tubes exclusively. It sounds like the combination of recoil spring, buffer, and lower receiver tube works, so find the difference. Change the bolt carrier catch with the receiver that works, etc, process of elimination.