reciever longevity

[UPSguy]

Over at TOS in a thread about Noveske's new carbine a certain dealer made the comment that the barrel will now outlast the rest of the weapon. This statement made me ask again a question never answered. Springs, gas tubes, gas blocks, barrels and bolts are consumeable items. What about the upper and lower recievers? What is their round count life expectancy?

[rob_s]

As a tangent, I'd love to see some kind of force diagram of the stresses that various parts of the rifle go through.

[Robb Jensen]

Uppers:
I've never heard of someone wearing out an upper receiver unless it was assembled or manufactured with a defect. A friend of mine recently had to fix one an unknown brand upper (ACME/WECSOG style) because of an auto launching forward assist assy. The roll pin hole was drilled to far away from the forward assist which allowed it to eventually to go AWOL. He drilled it slightly larger and used a roll pin 2-3 sized bigger and it's holding up well now.

Lowers:
I've seen warn out lowers where the hammer and trigger pins holes in the lower get oblong or way too large (more often on 9mms with and w/o full auto). For registered full auto civilian lowers there are guys who specialize in fixing this, on a semi-auto lower it's just WAY cheaper to replace the lower. I think most of the time the military takes a lower out of service is more for damage (cracked, bent, Kb'd gun etc.) then it is for being worn out. My little brother is a US Air Force TACP, when he went to basic in 1993 he had a M16 (as in no A1 behind it), until the last couple of years he's used very old GUU/GAU-5s, which are older then he and might be older then me.

Just yesterday I had a guy bring an old Colt SP1 Frankengun that he just bought. He wanted to know why the safety selector wasn't clicking from moving it from safe to fire. It looked at it and it looked like someone had milled out a large portion of the inner bottom of the receiver. It had also been refinished in black Norrells. Anyway when I tried installing a safety detent and spring the detent and spring would jump out of the safety and wind up in the lower receiver while tightening the grip screw. The hole that the detent and spring 'live/work in' (within the lower rec.) was about 3 times too big. There was no evidence that someone might have been trying to make an illegal machinegun. I'm thinking maybe this was once a host (or was going to be a host) for a RDIAS or Lightning Link and somehow got damaged from poor milling (probably a Dremel) which is probably why the original owner was selling it.