After reading dozens of MIM (metal injection molded) threads over the last year, and working on tons of guns with MIM, I wanted to throw out some thoughts on the matter.  I'm no expert, but I do work on a lot of 1911s, and have some experiences I would like to share.  

I had a very lengthy conversation with my father in law the other day about MIM.  He's a metalurgical engineer, with metalurgy experience dating back to the late 60's in the military.  He is well aware of MIM technology, and enlightened me about the molecular characteristics, as well as the fact that there are different types of MIM.  One of the biggest points he made to me is that poor MIM parts in guns can most likely be attributed to low grade, inexpensive powdered metals.  Properly produced MIM parts with good metal should not lead to birttle parts and premature breakage.

What made me think about all this is how many people will denounce MIM, while others will say how MIM is just fine because they never had a problem in their one or two guns.  The truth is probably somewhere in between.

Over the last 5 years or so, I've noticed the following on guns I've personally worked on or seen in my friend's shop.  Kimber and Springfield use numerous MIM parts, and not all of the parts are prone to breakage.  Some parts that I've seen break after very minimal usage are hammers, slide stops, ejectors, ambi safeties at the joint, and firing pin stops.  Of the other numerous MIM parts, like grips safeties, exctractors, sears, disconnectors, mag releases, mainspring housings etc., I have seen no premature parts breakages.  

Of the parts I've seen break, only the hammers and slide stops rendered the guns inoperable.  The two ejectors I've seen were broken at the tip, and they were ectended models.  One had a tip that jammed the slide open, and the gun would not function.  I have not seen any breakages with non extended MIM ejectors.  All of the firing pin stops I've seen break have led to no gun stoppages, and usually the owner was unaware it was broken.  I have seen one bushing break, but I did not get to talk to the customer about it.  

Other issues with MIM parts are their unsuitabililty for tuning.  Extractors and sears come to mind.  Some sears are simply too soft to keep the angles cut for a trigger job, but are fine in stock applications.  Extractors seem to have difficulty holding proper tension, and can loosen after only a few hundred rounds.  I had an MIM sear the other day that was so soft during a trigger job, I had to replace it.  It was a Springfield.  Disconnectors seem to be a problem in Kimbers but that has more to do with being out of spec design wise.  

I guess the real point to this post is that you don't need to replace every MIM part in the gun, but MIM is an issue on some parts.  For those who don't believe that MIM breaks more frequently than cast or barstock, I can say that inmy experience it does.  Between the hundred or so guns I touch in a year, and the other few hundred my friend does, we have seen many premature breakages on MIM parts that we don't see on cast or barstock.   Considering that a hammer that shears its hooks, or plain cracks through the middle, will render the gun non functional, I always replace MIM hammers.  Same goes for the slide stop.  The rest is a mtter of preference.  

Like I said, I'm no expert, but I continually see people who are new to 1911s wondering what they should do about their MIM parts, or that they read somewhere that their gun will not work.  Most of the time you will never see an issue, but if you don't want to chance it, consider replacing the hammer and slide stop at a mimimum, and the rest as you desire.

While 'everything' may break at some point, I get the impression you are seeing more MIM parts failing than traditional parts – assuming an equal sampling of both.

On a firing range it really does not matter, worst case is you would lose a match.

Elsewhere it becomes more significant. Since no end user can possibly know the quality of MIM parts without destructive testing, there is no point in trusting your life to them.

On the other hand, how would one even know if a part was MIM?

The easiest way to tell if a part is MIM  is to look for small circular casting marks.  A traditional cast part has a seam.  MIM parts have little circles along with a seam.  

For me, I hate the idea of MIM, but I also try to keep it in perspective.  I would definitely trust my life on certain MIM parts.  These are the low stress parts, like mainspring housings, grip safeties, mag releases, etc.  They are not prone to battering.  

I've read different things about what is or is not MIM in various guns.  I know some of them are for sure, and others I've just read are.  

Springfield Armory:

-firing pin stop
-barrel bushing (not sure on this one, just read it)
-recoil spring guide and plug (not sure on this, just read it, and actually doubt it)
-extractor
-ejector
-hammer
-sear
-disconnector
-thumb safety
-grip safety
-mainspring housing (not sure on this, just read it)
-mag release
-slide stop

Kimber:

-same as above

Colt:

-some say none, some say the hammer and sear, but as far as I can tell, all of the above is cast now

Having worked in an industry that depended on MIM parts, I can tell you from personal experience, a good MIM part will last, a flawed MIM part wont, and the bad ones are FAR more rare than the good ones.


Its up to you to decide if you want to roll the dice and trust MIM parts.  Personally, if it doesnt puke out fairly on during the break-in period, I dont worry about it.


I lugged my Kimber around the other day without the least bit of concern for the MIM in it.

Quoted: Having worked in an industry that depended on MIM parts, I can tell you from personal experience, a good MIM part will last, a flawed MIM part wont, and the bad ones are FAR more rare than the good ones. Its up to you to decide if you want to roll the dice and trust MIM parts.  Personally, if it doesnt puke out fairly on during the break-in period, I dont worry about it. I lugged my Kimber around the other day without the least bit of concern for the MIM in it.

C'mon man, you just sound way too rational!

I think MIM is fine for some parts, not good for other parts. Any part that is subject to striking, sheer, or impact is not an area I want MIM. Same for parts that have to hold tension as a spring would. Just not a good choice there. I do not mind it in certain places as it brings the cost of the weapon down, and it can be held to tight tolerences without much machining. Problem with bad MIM parts is that they look perfectly fine, no outward signs at all of the flaw.  I think part of the MIM problem is that sales are high and I wonder if the parts are being brought up to and lowered from temp properly. Speeding up in either area could cause some of the problems that are seen.

Soft MIM sears are not industry norm, Colt has MIM sears I believe and they are plenty hard on the surface, yet they are not brittle. I am unsure how deep the surface hardness is tho, maybe some-one knows?

Most of the people banging the no-MIM drum have no earthly idea what MIM even stands for.  If they did even the slightest bit of research on the process they might actually get a clue.

In 99% of MIM failures they will break VERY early on in their lifespan.  This is because 99% of MIM failures are due to air pockets in the part.  This has also become far more rare today than it was 10 years ago when Kimber began using MIM parts.  The air pocket becomes the weak point, and the part almost invariably fails at that point within a few hundred rounds.  Oftentimes you can see the air pocket with your naked eye, other times it is a series of very tiny air pockets that aren't visible.

The bottom line is that if I was buying a $2k+ custom gun I would expect all the parts to be barstock, but I carry one Kimber or the other every day and don't give the MIM a second thought.  You are less likely to face a MIM breakage on a broken-in pistol than you are to actually need the damn gun to begin with.

The hysteria over MIM has become rather comical of late.

I am curious RE:Colt though, as I have heard all sorts of claims from them being MIMless to having the same MIM parts as a Kimber.

Does any one know of after-market availability of MIM parts?

I just curious as to the price difference between MIM and bar-stock:

(Sear, hammer and slide-stop)

Is it really worth $10-$25 in the total price if the gun to run the risk
of premature breakage/wear-out of a part that upon failure could cost you your life?

No, I'm not implying that MIM are junk...

But being in the metal-cutting business for 25 years, I know that porous steels (MIM, cast)
do not wear the same as tightly-packed microstructure, drawn/rolled barstock-type steels do .

Of course, if you only put 250 rounds through your .45 a year I guess MIM could last a lifetime...

Quoted: But being in the metal-cutting business for 25 years

Of course, if you only put 250 rounds through your .45 a year I guess MIM could last a lifetime...

I find it odd that those two statements would be made by the same person.  Perhaps you can enlighten us as to what "metal cutting business" means.

Having personally witnessed MIM failures a couple of times at the range I worked at, and after talking to the manager/1911 smith I worked with who shared many more MIM failures I would not trust my life to one. Yeah, for a range gun it might be a different matter but even on those I'd get the parts swapped out - who knows, you might find yourself having to defend your life with one of them someday. That's my opinion, YMMV.

'Metal-cutting business"

Read: Prototype Machinist for in Aerospace/Defense 25 years

Quoted: Most of the people banging the no-MIM drum have no earthly idea what MIM even stands for.  If they did even the slightest bit of research on the process they might actually get a clue. In 99% of MIM failures they will break VERY early on in their lifespan.  This is because 99% of MIM failures are due to air pockets in the part.  This has also become far more rare today than it was 10 years ago when Kimber began using MIM parts.  The air pocket becomes the weak point, and the part almost invariably fails at that point within a few hundred rounds.  Oftentimes you can see the air pocket with your naked eye, other times it is a series of very tiny air pockets that aren't visible. The bottom line is that if I was buying a $2k+ custom gun I would expect all the parts to be barstock, but I carry one Kimber or the other every day and don't give the MIM a second thought.  You are less likely to face a MIM breakage on a broken-in pistol than you are to actually need the damn gun to begin with. The hysteria over MIM has become rather comical of late. I am curious RE:Colt though, as I have heard all sorts of claims from them being MIMless to having the same MIM parts as a Kimber.

Well I have seen several safeties SNAP in two that were MIM. I have never saw that before either. Sure, Colt has MIM, Sear, disco, plunger HSG, and a few other small bits [used to use MIM extractors, but went back  to tool steel after problems with them] The sear is the highest stressed part that is MIM in a Colt but I do not hear of problems with them. They seem to have the surface hardening down OK and it's deep enough to do a "trigger" job on it tho I personally would not bother. I'd get a non MIM one instead if I was doing that. However, Colt has nowhere near the MIM parts a Kimber has.

MIM parts suck.
I had the hammer on my SA break in half after 150 rounds,and SA said it would be 2 months before I got it back. I sold it after it was fixed.
Have two Kimbers now, no problems as of yet.

Quoted: MIM parts suck. I had the hammer on my SA break in half after 150 rounds,and SA said it would be 2 months before I got it back. I sold it after it was fixed. Have two Kimbers now, no problems as of yet.

Quoted: Of the other numerous MIM parts, like grips safeties, exctractors, sears, disconnectors, mag releases, mainspring housings etc., I have seen no premature parts breakages.

Broken MIM mag catch from my Kimber, which rendered the gun inoperable. Luckily it happened at the range...

Quoted: Perhaps you can enlighten us as to what "metal cutting business" means.

FWIW, there are alot of campanies out there that do nothing but cut metal for other companies. I worked at one for awhile as a plate saw operator. Boring, boring, boring job.

Quoted: Quoted: Of the other numerous MIM parts, like grips safeties, exctractors, sears, disconnectors, mag releases, mainspring housings etc., I have seen no premature parts breakages.   Broken MIM mag catch from my Kimber, which rendered the gun inoperable. Luckily it happened at the range... www.hunt101.com/img/334649.jpg

what was the round count on the gun when it happened?

Quoted: Perhaps you can enlighten us as to what "metal cutting business" means. FWIW, there are alot of campanies out there that do nothing but cut metal for other companies. I worked at one for awhile as a plate saw operator. Boring, boring, boring job.

which is kind of my point.  Standing around & operating a piece of equipment hardly makes one an expert on metalurgy.  That's like assuming that a form carpenter knows anything about concrete mix design.

Roughly 800 rounds, or so. I had shot all of the "range ammo" I had brought with me, reloaded my two 47D's with "carry ammo", and was waiting for my buddies to finish shooting so we could all pack up and leave together. Well, I got bored standing ther waiting so I decided to empty one of the mags full of "carry ammo" at a target. Bang, bang, mags falls out. I checked the mag catch, and it seemed to be ok so I stuck the mag back in and fired a couple more rounds. Bang, mag hits the ground again. This time it was obvious that the mag catch was broken.

What would've happened if I hadn't decided to shoot my "carry ammo" while I waiting? What if I had just loaded it and stuck it back in the holster expecting it to work when/if I needed it?

OK, now I feel I must defend myself:

Prototype machinists work on EXPERIMENTAL parts;
working with EXOTIC metals:

Invar. Kovar, Stainless steels, fiberglass, plastics, aluminum, tool steels.

I never claimed to be an expert, however I have LOTS of experience with CASTINGS,
FORGINGS, and MIM (Metal Injection Molding)...

I would PREFER forgings to MIM and castings.

That's where my EXPERIENCE comment figured into my comments....


HAVE A NICE DAY!

I have mixed feelings on MIM. My Colt sear, which I just retired, has almost 35,000 rounds on it and it was fine. Same for the disonnector which I'm still using.

But, on this thread and others I've seen broken mag catches and thumb safeties. Breaking parts like that bothers me. I've seen cracked cast thumb safeties(1 actually), but it cracked...not snapped so you had ample warning.

I was dissappointed to read MIM hammers can be a problem. I thought they had the trigger parts working with MIM. Working, to me, means a reasonable life span given the cost of parts.

Shamelessly copied off pistolsmith.com:

This was posted on the 1911 Forums by a Colt Employee.

Colt parts

MIM
sear
mag catch
disconector
plunger tube

CAST
safety lock
grip safety

FORGED
slide
receiver
barrel
slide stop

MACHINED from bar stock
hammer
all pins
bbl link
bbl bushing
trigger
ejector
firing pin
firing pin stop
extractor

LOOK AT ALL THE QUALITY GUNS NOW AVALIABLE AT REASONABLE ,AFFORDABLE PRICES.I LIKE PROGRESS.MIM WORKS FOR YOU AND ME BROTHAS!

Quoted: Shamelessly copied off pistolsmith.com: This was posted on the 1911 Forums by a Colt Employee. Colt parts MIM sear mag catch disconector plunger tube CAST safety lock grip safety FORGED slide receiver barrel slide stop MACHINED from bar stock hammer all pins bbl link bbl bushing trigger ejector firing pin firing pin stop extractor

That sounds about right, I, for the life of me could not remember if the mag catch was MIM or cast. so I left it out. Colt has the least amount of MIM of all the mass produced 1911s. The hammers on my SAs look absolutely cheapo compared to my Colts. Look like they came on a kids toy gun.

Sure alot of people have success with MIM. Like said before, it's a dice roll. All parts reguardless of material or manufacturing method are prone to some sort of failure.

It comes down to preference. I prefer forgings, although MIM has a decent track record when compared to the production numbers.

It's a preference with very little relevance to the casual shooter. I still prefer the strength of a forging, whether I need it or not though. Metal injection is plenty good enough for majority of the 1911 market. Those are just my opinions though.

Kimber fixed rear sights are MIM as well. They have a pocket in them to make them lighter, and the marks from being pushed out of the mold.

Soooooooooooo, if I were to go looking for aftermarket parts how would I no if they were MIM? Assuming I'm not actually looking at the part in front of me.

 With respect to many of the above comments on MIM, here is my take:


MIM is a cheap way of making a part that looks right and is actually about halfway right.  Okay....maybe three quarters.

Essentially powdered metal with a flow agent and binder mix is injected into a net or near net shape mold. The lack of subsequent post processing is what makes this a very economical process. The amount of time saved in manufacturing by using the MIM process is immense.  Anyhow the metal/binder matrix is compressed under VERY heavy pressure so that the binders hold the part in shape. The part is then ejected from the mold and then transferred to a series of heat treat processes. The first of which removes ( melts out ) the binder and other agents from the matrix. The second sinters the metal so that cohesive molecular bonds are formed between the compressed molecules of steel.

Between the compaction and the sintering processes the parts are very brittle and any flaws inherant in the original forming process or the transfer process are passed along to the part.

The molecular density of a MIM'd part is about 80 to 90 percent of a conventional barstock part. HOWEVER the molecular STRUCTURE is, in no WAY, SHAPE OR FORM even close to that of a forging or barstock.

Thanks...I'll stick with barstock or a forging.....the only part left on my Colt that is MIM'd is the plunger tube.

Friends don't let friends use MIM!!!!

Quoted: Soooooooooooo, if I were to go looking for aftermarket parts how would I no if they were MIM? Assuming I'm not actually looking at the part in front of me.

Many times there is no way to tell.  If it's in Brownells, then it's most probably listed.  If it doesn;t say what it is in Brownells, then it's most likely cast, and if it's barstock, it will say so.  Recently, I got two Briley barstock disconnectors that were MIM, as was one that member FROST18E got, and I'm sure that was on Briley and not Brownells.  Sometimes you just never know.

If you are wondering, ask here.  I have used so many 1911 parts and worked on so many different brands, chances are I will know.  Take care.

I do not like MIM
I do not like it in a Colt,
I do not like it in a bolt.

I do not like it on my gun,
MIM is no fun

I will not buy it in a box
I will not shoot it at a fox

I know, enough already

Quoted: I do not like MIM I do not like it in a Colt, I do not like it in a bolt. I do not like it on my gun, MIM is no fun I will not buy it in a box I will not shoot it at a fox I know, enough already

I'm now integrating this into the reading for my two year old.  Teach them right, I say...

Has Kimber  used MIM from the beginning?   Have they increased the # of MIM parts over the years?

They've always used MIM parts. As far as I know, they've always been chock full 'o' MIM, with the exception of the frame, slide, barrel, springs, trigger, grips/screws, and MSH.  

Somebody please correct me if I'm wrong...

LOL  glad you guys liked it

The MIM gods must've read it too because recently I was at the range and loaded a magazine into my Springfield...then just happened to look down at the shooting bench and saw something fall from my 1911 and it was the mainspring housing pin broke in half

Quoted: They've always used MIM parts. As far as I know, they've always been chock full 'o' MIM, with the exception of the frame, slide, barrel, springs, trigger, grips/screws, and MSH.   Somebody please correct me if I'm wrong...

In page 10 of their 2005 catalog, they (Kimber) claim they pioneered the MIM process in the gunmaking world, and that it "essentially has the strenth of those machined from steel".

Marketing is evil.

Quoted: "essentially has the strenth of those machined from steel".

Heh.

Quoted: Quoted: They've always used MIM parts. As far as I know, they've always been chock full 'o' MIM, with the exception of the frame, slide, barrel, springs, trigger, grips/screws, and MSH.   Somebody please correct me if I'm wrong... In page 10 of their 2005 catalog, they (Kimber) claim they pioneered the MIM process in the gunmaking world, and that it "essentially has the strenth of those machined from steel". Marketing is evil.

I sure would'nt hop on a stage and tout MIM as a positive point in my line of pistols.

I don't like MIM, at least in theory.  Never had a problem with it, but I have heard of problems.  Hell, the S&W 9mm semi's we had at the academy would succumb to a crack at the take-down pin on the frame.  Saw several examples in person, and I was not impressed.  Granted, those guns were shot a lot, but sheesh.  Plus, they were chock-full of MIM, however I didn't witness any broken MIM parts.  Personally, I would love to be able to afford a $1200 Rock River 1911 that has no MIM, but since I already have my defensive pistol (HK USP 45F) broken in and sitting in my nightstand, I don't think that I really need a $1200 RRA non-MIM gun.  Hell, if I want a non MIM gun, then all I have to do is get a Kimber I like, and rid it of the MIM parts, yes?

Quoted: I don't like MIM, at least in theory.  Never had a problem with it, but I have heard of problems.  Hell, the S&W 9mm semi's we had at the academy would succumb to a crack at the take-down pin on the frame.  Saw several examples in person, and I was not impressed.  Granted, those guns were shot a lot, but sheesh.  Plus, they were chock-full of MIM, however I didn't witness any broken MIM parts.  Personally, I would love to be able to afford a $1200 Rock River 1911 that has no MIM, but since I already have my defensive pistol (HK USP 45F) broken in and sitting in my nightstand, I don't think that I really need a $1200 RRA non-MIM gun.  Hell, if I want a non MIM gun, then all I have to do is get a Kimber I like, and rid it of the MIM parts, yes?

I suppose you could...but all you'd have left is a barrel, slide, and frame.

I work for a company that has a number of high speed packaging machines. We had a problem with some of the small parts (that cycle rapidly thousands of times a day) breaking frequently so we had an engineering firm design replacements. They were manufactured, installed and have run for months on end without failure. The original parts were barstock and forged. Almost all the replacement parts are MIM. A well designed and manufactured MIM part can be designed to last  longer than a marginally made forged part. Could the forged parts have been made better? Yes but the MIM works and is much less expensive to manufacture.

I had two MIM parts break on my Kimber; the thumb safety broke, on the flat part close to the pin.  Kimber sent me a new lever, and next time I went to the range, the windage screw in the rear sight broke in half (during shooting; I was not adjusting the sight).  I had a few thousand rounds through the pistol before this happened.  

In both cases, Kimber customer service was excellent; nevertheless, my confidence in MIM parts has plummeted.

-tjg

So if a guy were to buy a new Kimber, and despite all the reports of the MIM in others guns being fine,  wanted to replace all the MIM parts listed on page one with steel:  would it be something that he could do himself without much know how or tools?  If not, where would you recommend sending the gun to have it done?

You'd be much better off buying a Les Baer, Wilson, Nighthawk, etc. The overall cost would be about the same, but the resale value would be much higher.

Quoted: You'd be much better off buying a Les Baer, Wilson, Nighthawk, etc. The overall cost would be about the same, but the resale value would be much higher.

Thank you sir.

.

Stasher1,  looks strangely familiar.

I was under the impression that if a MIM part made it past break-in (about 1K rounds) then it would probably be alright.  After the 3K round mark a MIM mag catch let go on my Kimber Ultra CDP-II.  While I completely understand ANY part can break, the mag catch doesn't strike me as the kind of part which takes such abuse that it would be prone to early failure.  Several 1911 gunsmiths and experienced 1911 shooters agreed.  I no longer own the Ultra CDP-II.  My carry gun is a Les Baer Stinger, sans MIM.

I currently own a Kimber (series-I) 5" Custom Classic.  It is bone-stock and has been my beater-training-fun gun fo over 5K rounds.  It has zero parts breakage to date and is reliable to a point of being boring.  

Jolly Roger, I have a Kimber, doing exactly as you suggested.

The pistol cost 450 used.
Parts I can do myself : slide stop, extractor, firing pin stop, mainspring housing, pin set
That runs about 175, I think.

Then I'm sending it off to a reputable smith to replace all the rest of the MIM as well as do some other modifications ( checkering, new sights). Thats going to run around 1000 total.

So, in this case I am looking at about 1600 invested.

When complete , the pistol will compare in features to Les Baer Thunder Ranch 1911, which
I see listed for around 1700 (Brand new).

Probably makes more sense to purchase the Les Baer.

Guess I'll just have to tell the wife unit I need another pistol...

Personally, I won't have any MIM parts in my 1911's.  However, some guys seem to like MIM and apparently have good luck with it.  I just can't believe that a sintered metal part has the strength of a part machined/edm from barstock.  Just my opinion.

Mike.

So when were MIM parts first used on Colt, Springfield, and Kimbers ?
Does my early Springer have MIM parts?  

I used to have both a Kimber and a Springfield, and never had anything break on either one. I bought a Para single action 1911 used last year however, and the hammer safety broke on it. Para sent me another one, but it felt like plastic, and just didn't feel right. I traded it off after that.
Even now, I don't think I could bring myself to buy a Para again.

I just recieved ( two days ago) a Wilson Combat tactical mag release, appears to be MIM.

So now I'm wondering, just where is a guy gonna have to look to find non-MIM parts?
I see a lot of Ed Brown parts are apparantly barstock-derived, some from Wilson are listed as such, and others of course, but does any body know of a supplier that offers a complete line of internals for 1911 that are not MIM?

I love my old 1911, and the only MIM part in it currently is that aforementioned Tac release, and I'll run it for awhile and see what happens. But I've got plans to build some new pieces for myself in the near future, just because I seldom get the chance to build stuff for myself, I wanted to go from bare frame and slide, mostly just for the satisfaction of it.

But where or where do ya gotta go to get some straight-steel parts? Any ideas?