So...does that look like about 5k rounds?Originally Posted by Failure2Stop
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Senior Member
So...does that look like about 5k rounds?
Industry Professional/Moderator
Yes.
Nothing abnormal or excessive.
Senior Member
Cool. If I'd known, I'd have taken pictures every 500 rounds.
Senior Member
Not being funny, dead serious...
Do you mean it's like looking at a horse's teeth to determine approximate age?
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Senior Member
Don't look a gift rifle in the cam-pin pocket!
Senior Member
lol...good one
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Industry Professional/Moderator
As I know pretty much nothing about horses, or why they seem to be so elusive about their age; and I assume that you are saying that it is an imperfect observation that doesn't really give any information other than roughly how many meals have occurred, then yes.
Industry Professional/Moderator
Heh.
Well played.
Senior Member
I wouldn't concern myself with an example of one that would not be considered abnormal. Wear is going to happen with use and is normal.
What concerns me more are signs of excessive and/or abnormal wear.
A more boring subject could be examining the different wear traits. Different variants of the same base receiver do not act the same in this aspect. Some wear evidence tends to lead to use by different traits of their operating system. It doesn't take long to go into minutia when you look into the variable stack up. For the most in operation, there is little issue.
Senior Member
Looking at this in a very basic way. When the round fires, the carrier is preloaded by the magazine tension upwards. The carrier is preloaded with the the hammer forward, the action spring tension stays forward pretty much during this initial cycle portion with its respected values. During initial carrier movement rearward, magazine tension remains, the hammer tension begins to move its force from forward to upward. After a short carrier movement rearward, caming to unlock the bolt results in a torsional twist in opposition to the loading. The amount of twist or torsional tension can depend on how much force is required to operate the system. The system loses magazine preload upwards after it passes the magazine. The carrier maintains a preload from the hammer/spring force upwards, until the hammer movement is captured by the disconnect, ideally this would happen within the carrier ramp, but it tends not to in high speed video showing positive disconnect retention in too many late. Neither are equal across the the entire section of the carrier. The result is a "tilted" preload. Going forward, initially the bolt catches a new round, the caming resists with a torsional twist upon the carrier. The carrier has a "twist" that continues through feeding through the magazine. Evidence shows that there can be a slight reduction in torsional tension from the time the round clears the magazine lips to initiate locking, that time is minimal, but can exist. The locking of the bolt, with the magazine tension applied adds both a torsional and upward tension. When the system is "at rest" and ready maintains preload from the magazine and action spring.
Not really simplistic, but that's about as simplistic as it get when looking into tensions that may induce a wear pattern into this system.
An M16A2, M4, MK18, and other variants all have the same basic signs, but they are not the same overall
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