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Discussion Starter #1
Hi Everyone!

Just came back from firing my new SIG 556 classic for the first time. I noticed what I thought was peculiar damage to the shells after extraction.
Is this damage common for this rifle?



What causes this type of damage? what part of the rifle is the shell contacting?

Thanks for your help, I'm new to rifle ownership so sure appreciate having experienced people to ask questions of.

Tom Morris
 

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I get that, from the brass vigorously hitting the receiver on the way out, and then hitting, well, whatever gets its way as it is hurled at 750mph on its way to the next county...
 

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It's normal deformation and the shell hits the back of the ejection port, flips around and hits the side of the reciever just behind the ejection port, then will fly off to the right front.

Over time you'll see wear on the finish on the reciever (Brass kisses) from the ejected brass impacts. A lot of people like them (a sign of use), and a lot of people don't like them, and use tape or velcro just behind the reciever to protect the gun.

What you should do is have a look at the case head/rim for any signs of hard extraction or overpressure from time to time.
 

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Tom Morris said:
Just came back from firing my new SIG 556 classic for the first time. I noticed what I thought was peculiar damage to the shells after extraction.
Is this damage common for this rifle

What causes this type of damage? what part of the rifle is the shell contacting?
...this type of deformation is common with most assualt rifles...the degree of the deformation varries with the brass used...that is...it's composition...which will affect it's physical and chemical properities...such as it's indentation hardness...elasticity...bounce characteristics and so on...

...basically...on the 556...the empty shell casing is forced to release from the extractor by the ejector contacting the shell base as the BCG moves rearwards at a high velosity...causing it to move outwards and sideways...it rotates/pivots as it impacts the face of the ejection port window...then continues to rotate/pivot slapping the angled portion of the reciever directly behind the ejection port...at this point it has rotated 180 degrees...it then bounces off this area and fowards about 15 feet to about the 1 to 2 o'clock position...
 

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When you think about a case ejecting, when the ejector hits the rim, and the extractor is still moving back, the case will initially spin about the axis of the extractor. This imparts some sideways and rearwards translational velocity to the case, since the case CG is forward of this pivot point. However, as soon as the extractor lets go, the case will spin about its CG.

As Ullie described, the rotational rate versus the sideways/backward motion of the case is such that the case will do a 180 flip, and the case mouth will hit the deflector first.

Art
 

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Discussion Starter #7
Thanks for the replies. Glad to know there's not a problem with the rifle. I'd love to see the extraction in slow motion..
 
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