[TrickyD76]

Got the call from my FFL telling me my MPX had come in. I did a quick inspection and everything looked good. I got her home and disassembled her for the initial cleaning and lube. When I was wiping down the bolt i noticed a strange mark on it. After closer inspection it appears to be cracked! A Sig CSR said there was no way it could be cracked, that he has seen them tested with "triple charges" and that the bolt is virtually indestructible. Took it to my LGS and they told me not to run it and that they thought it was cracked. Sent pics to Sig and they sent me a new bolt, but thats not the point. I went almost a month without my new $1700 gun... not very happy. Has anyone ever seen an MPX bolt crack? And how exactly do you "triple charge" a little 9mm case?!

 

[MrMcGoo]

The crack in your bolt may have been from a proof charge at the factory. Or it may have been poorly molded and processed MIM.

Triple pressure charges merely need a very fast burn rate powder which comes from added nitro.

Cracked bolts are very rare when new. Cracked extractors are more common.

Cars and firearms can't be exchanged when defects show up. You have to go through warranty service. If warranty service on a gun doesn't get the job done, SIG may exchange the weapon. Poor warranty service on a car rarely results in a refund or exchange.

Bill

 

[crosseyedshooter]

Got any pictures of the crack? I’d like to know what to look for.

 

[Thompson415]

Depending on the powder you can create a double or triple charge proof load. I too would like to see pictures of this crack

 

[TrickyD76]

Cracked bolt 1

 

[TrickyD76]

Cracked bolt 2

Depending on the powder you can create a double or triple charge proof load. I too would like to see pictures of this crack

Cracked bolt 1

 

[Smokey99]

Strange looking crack. Know anyone in welding? Have them run a dye penetrant check.

 

[Shagbark]

I enlarged a section of your picture a gazillion times. Sure looks like a crack to me.
It's a little hard to see but there is pitting in the bolt on the lower side of your chalk line.

 

[Jayrod9727]

Looks like maybe a deep scratch but one way to tell is with a process called FPI Fluid penetrate inspection. I used to work in the aircraft industry and that's how we would inspect parts. Better safe than sorry though you made a good call. I would still want to know for sure just to satisfy my curiosity.

 

[Smokey99]

Looks like maybe a deep scratch but one way to tell is with a process called FPI Fluid penetrate inspection. I used to work in the aircraft industry and that's how we would inspect parts. Better safe than sorry though you made a good call. I would still want to know for sure just to satisfy my curiosity.

Yep! That is what I was referring to. Go to local Welders supply store and buy a can of Dye Penetrant and a can of Developer (preclean with mineral spirits).