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Non-Steel?

1025 Views 9 Replies 4 Participants Last post by  SMMAssociates
I'm confused about all the negative comments regarding MIM. There are a number of reputable pistol manufacturers using non-steel parts for just about every part of the gun - slides perhaps being the single exception. Service M9s have alloy frames, plastic (excuse me, "polymer") GRs, multiple plastic coated smaller parts; polymer frames are ubiquitous, even lined polymer barrels in some weapons. Do I really need a moly steel front sight, or magazine release button? MIM seems like a reasonable way to produce tough parts in low-stress areas. At least, maybe, better than "polymer?" Any metallurgists or mechanical engineers around? :scratch:

Doc H.
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MIM is for metal injection molding.The parts in discussion are steel or stainless steel. The process involves injecting metal powder into a permanant mold. I believe there is some sort of binder to make the molding hard enough to handle, parts are molded to a very specific oversize. Afterwards they are removed from the mold they are heated to a temp high enough to fuse the metal, when cooled the part shrinks to the correct size. This process is in wide application in the aerospace industry. Once the tooling is made many parts can be made from it with relative ease (read cheaper) Hope this helps. Cold Iron
 

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Discussion Starter · #4 ·
Clear and understood; there seems to be a sentiment that this process produces an inferior steel part however. My question was does this produce a part that is substantially less strong than one made from a material that is non-steel. Would seem that MIM produces a part that is at least as strong as "polymer," which is used more frequently in all sorts of pistol parts. I don't understand the negative connotations of "MIM."

Doc H.
 

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MIM parts are castings as opposed to forgings (hot or cold) or machined from bar (billet). Generally speaking castings are considered inferior to the latter. However, Ruger uses lots of castings (lost wax) in their firearms and they are almost indestructible. Cold Iron
 

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ColdIron said:
MIM parts are castings as opposed to forgings (hot or cold) or machined from bar (billet). Generally speaking castings are considered inferior to the latter. However, Ruger uses lots of castings (lost wax) in their firearms and they are almost indestructible. Cold Iron
There is a big difference between castings and MIM. You may want to read the link above to understand.
 

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Discussion Starter · #7 ·
From what I'm beginning to understand, seems like the negative issues with MIM are not that a durable, quality part cannot be produced, but that the process itself may produce more defective parts, whose defects may be undetectable until failure. Close?

Doc H.
 

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AHancock said:
From what I'm beginning to understand, seems like the negative issues with MIM are not that a durable, quality part cannot be produced, but that the process itself may produce more defective parts, whose defects may be undetectable until failure. Close?
Doc:

Close....

IMHO....

(I was in the Plastics business for a long time, including a molding company. Worked for 'em, that is....)

I think that nondestructive testing at the 100% level (or a 100% confidence level, not quite the same thing) is possible, but may be expensive.

IMHO, forged or cast parts will be subject to machining that should show up hidden failure points - voids, mostly - whereas MIM parts are pretty much tossed into the gun once they cool down from the final sintering process.

Testing is the key, I think. I suppose there may be metallurgical reasons to avoid MIM parts, but I don't think that adequate testing wouldn't solve that problem.

There are also some magic advantages to MIM - you can mold stuff you can't otherwise make at all, or more likely, stuff that would cost a lot more when made by more conventional means.

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Discussion Starter · #9 ·
Thanks Stu! Seems like the trick is getting a reliable supplier with good QC, and double-checking through extensive random testing for failure - less cost in manufacturing, higher costs in slower production and more extensive failure testing (probably fewer guns get off the line). If you skip steps to save money (Kimber?), you get more new gun failures and more unhappy customers. So far, so good w/my Tactical Pro; first 100 rounds no FTF or FTE, 3" offhand (Weaver) @ 25 yds; happy with that at my age and eyesight! Gun got picky as it got dirty later, but expect that with any new auto. No broken MIM parts as far as I know; looking at a Wlson CQB though; like the detachable light rail! Thanks again; great forum...:)

Doc H.
 

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AHancock said:
Thanks Stu! Seems like the trick is getting a reliable supplier with good QC, and double-checking through extensive random testing for failure - less cost in manufacturing, higher costs in slower production and more extensive failure testing (probably fewer guns get off the line). If you skip steps to save money (Kimber?), you get more new gun failures and more unhappy customers.
Doc:

I think you're correct....

Unfortunately, us users can't adequately test MIM parts without beating them to death, too, which may be a small problem, and they can fail instantly and without warning. But as a general rule (as was mentioned before), they usually fail quickly.

Also, when thinking about Kimber, don't forget they're selling a lot of guns, and we generally only hear about the ones that fail. Nobody but me would post "my MIM magazine release didn't break on the range yesterday." :)

I broke an extractor on a Para Tac-Four ("LDA" double-stack Commander clone) about ten months ago. Almost certainly some too-hot reloads. I don't think a forged or machined part would have failed that way, but it'd had several thousand rounds through it by then, so I have to write it up to "who knows?".

So far, so good w/my Tactical Pro; first 100 rounds no FTF or FTE, 3" offhand (Weaver) @ 25 yds; happy with that at my age and eyesight! Gun got picky as it got dirty later, but expect that with any new auto. No broken MIM parts as far as I know; looking at a Wlson CQB though; like the detachable light rail! Thanks again; great forum...:)
Great forum, great bunch of guys. I bought my first Kimber about a month ago, and couldn't be happier. 100% function out of the box, and it's all steel, and missing the lawyer-inspired features, too. (OK, I wouldn't mind a loaded chamber indicator.) I'll probably swap out the extractor and the magazine release when I get the itch, but we're just getting past the "probably will fail by now" time.

I hope you enoy the Tactical Pro.... Seems nice. Mine seems to have a tight chamber - it doesn't like my buddy's reloads, but will take my usual "you bought what?!" stuff. Once in a while the extractor refuses to let go of a case. Dirt seems to be the major issue, and it just has to wear a bit. My buddy just bought a small Kimber, and we were having all kinds of silly problems. I think the disconnector was refusing to move out of the way when the slide was operated. It just suddenly stopped doing that. (Before he'd let me take the gun apart....) Minor lockup issues now, but it's shooting in well. I like mine better, but would have bought his without a question. Now if I could only get him to trim his cases while reloading....

Regards,
 
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