MIM Parts - Good, Bad, or just Ugly?

This is a discussion on MIM Parts - Good, Bad, or just Ugly? within the Defensive Carry Guns forums, part of the Defensive Carry Discussions category; For those of you not familiar with the term, MIM stands for Metal Injection Molding if I'm not mistaken and please correct me if I ...

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Thread: MIM Parts - Good, Bad, or just Ugly?

  1. #1
    VIP Member Array Euclidean's Avatar
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    MIM Parts - Good, Bad, or just Ugly?

    For those of you not familiar with the term, MIM stands for Metal Injection Molding if I'm not mistaken and please correct me if I am.

    Here's an overview of what MIM is and how it is used in general.

    Metal Injection Molding or MIM, also called Powder Injection Molding or PIM, is a net-shape process for producing solid metal parts that combines the design freedom of plastic injection molding with material properties near that of wrought metals. With its inherent design flexibility, MIM is capable of producing an almost limitless array of highly complex geometries in many different alloys ranging from stainless steels, alloy steels, and soft magnetic materials, controlled expansion materials (low CTE), and custom alloys. Design and economic limitations of traditional metalworking technologies, such as machining and casting, can be readily overcome by MIM.

    Today, MIM is serving critical performance applications in a wide range of industries and products including, automotive, aerospace and defense, cellular telephones, dental instruments, electronic heat sinks and hermetic packages, electrical connector hardware, industrial tools, fiber optic connectors, fluid spray systems, hard disk drives, pharmaceutical devices, power hand-tools, surgical instruments, and sporting equipment.
    I'm no expert on this process or the materials it produces, but more often than not these parts are winding up in our guns.

    I'll speak mainly to what I know about here, and in my experience I've had a firearm or two with MIM parts and I'm convinced they are not inherently flawed and that the material is as strong as anything.

    What I don't like about it is that MIM is nothing more than a cost saving measure for a gun manufacturer; replace a couple of forged parts with MIM, keep prices the same, and save some $$$ for yourself. Smith and Wesson I'm looking at you.

    IF there was any perceivable price benefit to the customer for the use of MIM and not just more profit for the manufacturer who thinks I'm not going to note the difference, I wouldn't be worried about it, but alas such is not the case.

    Honestly my main beef with MIM on certain guns, Smith and Wesson revolvers in particular, is that MIM parts make an expensive and probably otherwise very posh firearm look cheap and shoddy. Case in point:



    Now it looks okay by itself but compare it to this speciment with the forged parts. The 686 is the one closer to the bottom.



    My photography may be crap, but you can see it for yourself sometime... hold a gun with forged parts against one with MIM parts and see which one looks like a $700 MSRP firearm.

    I realize what it looks like doesn't impact how well it works, but when I'm shelling out that kind of $$$ I expect a certain level of "fit and finish", including a little more attention to details like that.

    I wish forged parts could at least be had for those of us that care for them or that manufacturers would at least hard chrome the MIM parts that are visible. My 625JM for instance is a great compromise... sure it's got MIM parts but they don't look like it.

    On a gun I buy for economy MIM parts are just fine, on a gun I buy because I want the best of its kind available, the MIM parts bug me.

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    I put this entire MIM issue in this context; one of the most accurate guns I've ever fired (and that I now own two of) was an acquaintance's Dan Wesson Model 15 .357 Magnum.

    That gun had the precursor of MIM, sintered metal (powdered metal pressed under high heat in a mold to form a part). The gun performed flawlessly according to him in thousands of rounds; he never had a part break, the gun was inexpensive (compared to S&W competitors) and what I experienced...it was beautifully accurate.

    I've read of Kimber owners having parts break in their 1911's...not only MIM, but steel/stainless steel parts too.

    MIM parts on a gun don't bother me...as long as they work, and I think they do.
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    Despite the cost saving aspect I do agree there are cases when a MIM part could be made to look better - but of course it'd add back on some cost!

    If the process is well carried out then there need be no major strength issues, however I do think the risk for inclusions is greater, and this could even be as simple as a gas bubble - something that could produce a stress and so failure point.

    The beauty of forging is the grain ''flow'' induced by the process and this does IMO make for a stronger part. With MIM this won't happen and I'll bet that with some components if tested side by side for both tensile and bending - the forged would almost always win.

    We are tho somewhat stuck with this change in manufacturing by some makers - pity, but fact of life.
    Chris - P95
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    VIP Member Array Bud White's Avatar
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    MIM is good if its done right.


    Ive never had a MIM part fail..

    Kimber seems to have a problem with it though ..At least those are the ones you seem to hear about most...

    Colt uses MIM as does springfield and everyone else anymore

    If they were all made of true Steel and hand fitted that 686 that is 700$ or so would go more for 2700$ no days

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    MIM Parts

    Metal Injected Molded part technology is an evolving fabrication process.
    They probably do have all of the bugs worked out of it these days.
    There are horror stories about early MIM parts...especially critical handgun parts.
    Thumb safetys just breaking in half & slide stop & barrel bushing breakage - gun sights breaking off. Whoops!
    My best guess is that if a MIM part does not fail right away then it probably will be OK for a good long time.

    I'm still quirky about changing MIM Colt pistol parts out for forged / machined parts. Just my personal preference.
    I admit that my opinion of MIM parts has been tainted by seeing "first hand" & early photos of pistol parts just breaking in half & folks "thumbing" off the thumb safety & having it just break in half & fall right off the pistol.

    That image still haunts me so I'm still staying away from critical MIM parts...if possible.

    And there IS a huge difference in the process between foundry cast metal parts (where actual molten metal is poured into a mold) and MIM...where metal powder is cold mixed with water & a polymer binder - dried and removed from the mold & then heated to cook off the binder and fuse the loose powdered metal together into a (hopefully) incredibly stong structural part.

    One other disadvantage of MIM is that it does not blue or polish too well.

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    Controls (thumb safety, slide stop, and grip safety) and ignition (sear, disconn, hammer) parts I'd like forged. Those are more critical IMO. Other parts MIM doesn't matter. The 1911 forums have an FAQ on forged, cast, and MIM parts. Good read.
    07/02 FFL/SOT since 2006

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    I have plenty of guns with MIM parts and I am not an anti-MIM crusader, but I personally had a Kimber in which the thumb safety snapped in two the first time I tried to apply it outside the store.

    They send me a new one, but I didn't keep the gun very long...
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    DDGator

    Some years ago & even not TOO long ago...I was very Anti~MIM So far as that I did not think that any MIM parts belonged on any primary carry firearm.

    It was not JUST what I read on a few web forums but, photos abounded on the Internet of broken MIM parts some were totally unreal.

    Now...I'm fairly MIM neutral since MIM parts are going to be the wave of the future to help gun makers cut manufacturing costs.

    I think some of the early problems with MIM were that in fusing a batch of parts...some parts did not attain full heat due to their location in the furnace & so did not fuse correctly.

    I've honestly not been hearing anything recently about MIM parts breaking & reverting back to powder on finished firearms...so (obviously) I guess they are OK now.

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    Just for point of reference time-wise, my Kimber with the "removable" thumb safety was purchased new about 18-24 months ago.
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    Removable thumb safety...
    But, your exact experience is what caused me to originally shy away from anything MIM.


    One MIM part that I think everybody absolutely should replace is a MIM extractor.

    I think I remember reading in an American Handgunner article that Kimber uses 13 (or thereabouts) MIM parts.

    Basically...Ditto: Me On This:
    "While it is all the rage, the use of MIM (metal injection molding) for small parts gives many people a queasy feeling. While a friend in the metalurgy business assures me that MIM parts CAN be just as good as forged/machined parts, the quality depends greatly on the alloy used and the care taken in the casting process and heat treatment. If you are "mission critical" you might want to consider replacing the MIM critical parts (hammer, sear, and disconnector in 1911s and whatever in other designs) with forged/machined parts as available."
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    VIP Member Array Bud White's Avatar
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    They ain't called Mimber for nothing

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    Never had a problem with my SA yet, if I do , then I will replace the MIM parts.
    "In matters of style, swim with the current; in matters of principle, stand like a rock." Thomas Jefferson


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    VIP Member Array Ti Carry's Avatar
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    Quote Originally Posted by Bud White
    They ain't called Mimber for nothing
    Springfield is loaded up with MIM too mister!

    I am NOT a fan of MIM parts and for the most part replace them with guns that have them and I carry.

    I would agree that if done right they are pretty good parts, BUT! I don't trust the makers to put the "best" MIM parts in. After all they are doing this to cut cost's, and replacing a few hundred broken parts per year when selling 50,000 guns must be O.K. with them.

    In all fairness I have seen cast and forged parts fail in the right conditions too but it is very, very, rare.

    Bottom line is, I don't like them! but as QK said I am tainted by the MIM breakage epidemic not to long ago. To be honest I would much rather (if buying a 1911) pick up a Dan Wesson for under $875.00 or a Les Baer from $1,300.00 to $1,500.00 on many models without MIM parts.

    Question, if the MIM parts are to cut cost and production time, WHY in the heck is a Kimber or a Springfield more expensive than a DW?

    DW uses a rap sheet a mile long with custom parts from Ed Brown and loaded with Wolff springs from the factory for about $850.00 for a PM-7 or C-BOB and about $875.00 for a new Razorback and it seems a Dan Wesson receives about half the credit of a firearm LOADED with MIM parts.

    I can't figure it out, must be that fancy advertising from the other makers. Because it is painfully obvious to me that a DW is the not only better made gun but the less expensive gun for what you get in the production line up.

    At this point I don't trust MIM, I don't like it in the critical areas at all.


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    IMO Kimbers problems with MIM is related to the company that supplies Kimber. If you accept poor quality, you get poor parts.

    I have never seen a S&W MIM part fail.

    No I do not know who the jobber is for either.
    Keep the shotgun handy!!

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    Addition:

    Obviously a person cannot just look at an investment cast part...or a forged metal stamping or a fully machined part & know in advance if it will be more prone to breakage or not.

    A forged part or machined part that is not tempered properly can also break. If it is not hardened properly then it will be too soft & it will deform & peen but, likey not break.
    An investment casting can have a void which may cause it to fail. BUT, ............that is very rare these days.

    the process of metal hardening & tempering has been with us for ages...it's pretty much a down~pat science these days.
    It is extremely rare for forged, machined, & Investment cast parts to catastrophically AKA instantly fail. Though they can (of course) eventually fail like everything else. Improper "fitting" of any critical parts can also induce failure no matter how the part was made.

    I'm (admittedly) a bit of a metal snob & I'll go for any older one piece machined steel Colt 1911 Trigger over any new 2 piece Nylon & stamped steel trigger. I'll also get rid of a plastic mainspring & switch it out for a metal one any ol' day. All of my Colt sears are switched out for older machined sears or aftermarket fully machined.


    It seems pretty RARE for properly made MIM part to fail these days also & had the MIM process not had its initial bad debut into the firearms manufacturing business....I would (for sure) be more tolerant of modern MIM parts.
    I'm cursed (or blessed) with a long memory so I'm still biased toward MIM.

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