Your extractor doesn't look abnormal to me. The extractor on the 870 doesn't sit tangent to the outside curve of the bolt, it's oriented "flat", or parallel to the top & bottom of the receiver. This may make it look cock-eyed, since the profile of the bolt curves "away" from the extractor on top, but that's where the extractor needs to be to grip the shell rim at the 3 o'clock position for proper feeding and extraction.
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That's why the extractors are chamfered on top, so that they sit more flush with the bolt's curved shape. The image you placed in your second post shows an improperly-machined extractor that lacks this chamfer, and gouged the receiver as a result. This is one problem with the machined (non-MIM) extractors, they can have dimensional variances or even missed machining steps, while the MIM parts (which, by the way, are also steel) are much more uniform since they all come out of the same mold.
Really, the MIM extractors work fine. Folks who criticize MIM parts (which
all 870s have) usually don't understand the differences between old-school pressed & sintered powder metallurgy, and modern metal injection molding techniques. Metal injection molding is an advanced process that can produce complex parts that are extremely consistent and precise, with density & mechanical properties that are virtually identical to those of wrought alloys, all at a very low per-part production cost (with sufficient volume).
This video does a pretty good job of explaining the process.
Remington is recognized as an industry leader in this technology, and has played a big part in developing and perfecting metal injection molding since the early eighties. Remington's award-winning
Powdered Metal Products Division has supplied MIM parts for the automotive, electronics, and tool industries; in addition to firearm parts for Remington guns, and guns from other manufacturers.
They know what they're doing when it comes to MIM part and process design.
