This.

My question is, how do you tell a gate mark from a cut off sprue?

Probably can't always but the size, area, and visual appearance of attachment might be one thing to look at.
  If you look at the videos on the cast parts they are cut off a solidified metal tree. Most of the AR parts I have seen that showed the attachment to the center tree has a large surface used to attach it like the end face of the trigger, the end of a selector, the extended face of the hammer, and the end of the bolt catch. They are cut off the solid metal tree leaving a large flat area that is later removed or smoothed.
 Some videos show the MIM parts that are made on trees being more like the plastic injected parts attached to something like a plastic model car or plane kit arrangement with small attachment points. Also in the MIM videos I watched the parts are removed from the small attachment to the trees before they go through the processing and shrinking of the part. Sometimes removal was done by machine and by hand in one video I watched.

The same way a Skilled Machinist can look at two pin gauges that are .010 different in size resting on a work bench, and tell you by looking which is smaller/larger.


MIM parts often have different external features than cast or billet parts with the same function.

I’m going to have to toss the BS flag on that first part. I are a skilled machiner and work with a bunch for the last 20 years and if one can tell you the difference between a 1/4” and 6 mm dowel pin have him repeat the feat. You will soon learn it was just dumb luck.

@ihv800

Here's the scoop....

"The triggers and hammers are MIM parts made of S7."

I should have the disco and bolt catch info in a few days.

This is straight from the horse's mouth.  

Back in the good ole days someone had a sale and Complete Anderson parts kits were like $7. Think I bought a dozen of them. Out of those dozen I think o was able to cobble like 4 complete kits that could actually function.

That would be easy, put them end to end. One is .014" higher and you can feel it, don't need to see it.

A concrete answer! Thanks for that. I'm guessing S7 is some sort of tool steel?

Correct.

S7 Shock-Resisting Tool Steel is an air or oil hardening tool steel that is characterized by very high impact toughness

You're killin' me, brother!  So, this is powdered S7 with some binding glue, squirted into a mold?  I have seen other parts and tools made from S7, but never a MIM.

Did I read the above post correct?  Do you have some MIMzies inbound for a torture test?

100% MIM S7, boss.

And negative, I swore off Anderson LPKs a long minute back.

Copy.  

I am truly starting to wonder how many MIM parts we have been receiving without knowing.

You and I went over this a few years back when I got those fucky PSA kits, I tossed them for being shit, but it never crossed my mind they were MIM.  I am now betting they were!

Yeah...I received some interesting trash a few times as well. Haven't been back since.

Mim is faster and cheaper than cast. The mold is permanent like plastic injection mold. It can be a good product if done properly, but the chance of inferior parts is higher than a cast part. Under no circumstances is it better than cast. If a cast part if bad, there are visual defects you can easily see. I do casting. With MIM, If the binder is not cooked out properly and all the small particles do not melt-bond together thoroughly, the part may look fine but integrally  it will be weak. Why take the chance. We are talking maybe $10-$15 difference. Fire control parts is not a place to go cheap. Do that on a hand guard or site or something. Craig

The premise was simply resting on a table and differentiating by sight. Holding them or or arranged in a manner to tell is a different manner.

Oops dupe