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Discussion Starter #1
I haven't fired it yet but while cleaning my 556R and I removed the firing pin from the bolt, it was caked with carbon, so I cleaned it and reinserted it back in the bolt.

I noticed the tension is a lot less than my 5.56 556 spring when pushing it down to remove the pin in the bolt.

Does the 7.62 use a less powerful spring or could this be a sign of a problem?

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Discussion Starter #3
What was throwing me off is the pin on the left (5.56) has stiffer and almost captive spring while the one on the right (7.62) is not as stiff and very loose.
I wasn't sure if something was broken or missing before taking it to the range and not having it ignite the rounds.


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A picture is worth a thousand words. That is indeed interesting. I never disassembled my 556R to that level, in the short time I had one. I can say though, that the 553R is just like the other 55x guns, when it comes to that spring, so it's interesting that the US 7.62x39 gun would be different. Does it apply enough tension that the firing pin is held at it's rear-most position when assembled into the bolt? If it does, I wouldn't be concerned about it. The internal geometry of the 556R bolt may be such that the spring seat is further toward the back of the bolt, in which case that slack would be taken up.
 

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Discussion Starter #5
When assembled the pin of the 7.62 seats and looks the same as the 5.56 the only way I even noticed was with the 5.56 I needed to press the end of the firing pin on a hard surface to get the retaining pin out, with the 7.62 I can easily do it with a finger.

It's probably normal but certainly had me guessing.



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I think I have an answer for you. The firing pin spring on your 556R is not as stiff as on your 556mm because of the harder primers on Com bloc & Soviet ammo. Therefore it requires a harder strike for reliable ignition than does 5.56x45 ammo, much of which is commercial .223 ammo. So your spring has to be weaker. As an aside, most AKs don't have a firing pin spring at all.
 

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The primers crossed my mind as well, but the return spring's purpose isn't to regulate primer strike force, but to prevent the pin from striking the primer unless the hammer is released. If you want to change the force acting on the primer, you'd address the hammer spring, not the pin return spring.
 

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Discussion Starter #8
I think I have an answer for you. The firing pin spring on your 556R is not as stiff as on your 556mm because of the harder primers on Com bloc & Soviet ammo. Therefore it requires a harder strike for reliable ignition than does 5.56x45 ammo, much of which is commercial .223 ammo. So your spring has to be weaker. As an aside, most AKs don't have a firing pin spring at all.
That makes sense and I think I was looking at it the backwards and that a stiffer spring would have more power when striking the primer when it's actually the opposite.

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