MIM Gun Parts?

[Joshua M. Smith]

Hello,

I learned about MIM, casting, forging, etc in college a while back.

MIM and casting always seemed to have about the same weaknesses in my mind.

After ordering and installing this MIM safety on my 1911, I got to taking a hard look on what's NOT forged in modern firearms.

Turns out, almost everything in non-custom guns is MIM. Armscor uses MIM frames (Armscor makes these for STI, RIA, and until recently, Charles Daly). Kimber is pretty much all MIM. Wilson uses MIM.

Remingtons have a lion's share of MIM parts and the company owns its own MIM plant.

Smith and Wesson revolvers are using MIM parts internally.

Colt uses MIM.

Ruger, if I read right, uses cast frames and slides with MIM internals.

They all hold up well. Yet people hate MIM.

Why? And what are your experiences with MIM?

I personally had ONE MIM part ever break on me. It was a joint on an ambi safety from first year Charles Daly 1911 production, and it had an obvious flaw. In other words, it was a goofed step in the process, not the process itself.

So, what are your feelings on MIM? Are they functional? Have they made all our firearms into crap?

Josh <><

[jaydubya]

My S&W 637 and 686+ both have them. I've fired several thousand rounds through each with no problems. I too am puzzled by the hatred -- no other word is strong enough -- that MIM parts have created.
Cordially, Jack

[VHinch]

MIM is good at what it does. It makes the production costs low enough to make lower priced guns possible. Your Charles Daly wouldn't have cost $400 new if it wasn't full of MIM parts. That makes a lot of guns, 1911's in particular, available in price points where more people can afford them.

I take them for what they are. I don't have a particular hatred of them, and I have plenty of guns that utilize MIM parts. The guns I carry however, do not use MIM parts. I understand that making that choice is going to cost me more, and I am willing to pay for the difference.

[Fat Boy]

I wasn't aware Ruger used MIM parts...is there a way to learn exactly what guns use MIM parts, and what parts they are?

[Joshua M. Smith]

I've seen some short lists on this lil' 'net crusade I'm on, but everyone's list seems to be different on who uses them.

As far as I can tell, only Nighthawk and (maybe) Brown don't use them.

Nighthawk states this specifically.

Josh <><

[davepool]

Okay, i have to ask the stupid question....what does MIM mean?

[Gun Slinger]

It is not a stupid question, man. :) MIM stands for Metal Injection Molding.

Not a metallurgist, but in the conversations that I have had with the two that I do know personally, they indicate that the process is a well respected one and that done correctly, the parts produced are adequate for most uses that they are put to in firearms.

The problem is actually one of perception. I'll elaborate.

Fact is, most equate the process as being synonymous with "sintering", a process that produces parts that are by comparison far weaker than investment cast parts due to the initial size of the metal particles used in that process. MIM uses metal particulates several orders of magnitude (100x-1000x) smaller than sintering and produces a higher density (read: less voids which serve as internal starting points for stress induced failures) and therefore much stronger, end-product.

When it comes right down to it, wrought/forged parts, MIM and sintered components can all fail and sometimes do, even when they are properly produced and all have their place in the modern manufacturing process.

If you've misgivings about them for whatever reason or just plain old don't like them, then do some research and find a product that suits your tastes. Just be prepared to spend a little (or a lot) more for what you want.

I, for one, don't worry about it to begin with and if I absolutely don't want a product that uses the technology, it is relatively easy to correct the "issue" or find a product that doesn't utilize the MIM process.

Regards,

[davepool]

Thanks, makes a lot more sense to me now that you've explained the process...and i agree, they should function well if the process is done correctly

[VHinch]

As far as I can tell, only Nighthawk and (maybe) Brown don't use them.

Those 2 are correct, as well as Les Baer. The higher end Dan Wessons are MIM free as well if I am not mistaken. You also won't find any MIM in the old Commercial Colts, which is one reason I prefer them and my Baer TRS for EDC.

[mtngunr]

MIM is still not as strong as machined barstock or machined forging....but, hey, we're only talking about something you might depend on to save your life.

MIM today is denser than earlier versions that had smiths refusing to try action jobs on them.

Colt has gotten away from MIM to a large degree, and never were they at the level of many current makers....and some of the brands mentioned here as MIM/cast free might suprise owners. Offhand, and without my list, Colt does NOT use MIM or cast for extractors, firing pins, hammers (aside from the 01911 and 01918) slide stops, bushings, frames, slides, plugs, firing pin stops, barrels, links, pins, plunger tubes....they briefly used MIM extractors which had a horrible failure rate, and have stepped away from cast plunger tubes due to loosening problems....sear/disconnector MIM, MSH cast, thumb safety MIM, mag latch MIM.....forgive me if I don't list more....

Personally have no problem aside from aesthetics on MIM non-stressed small parts, but aesthetics are a large part of what determines what guns I buy.....I won't buy a new Smith because I know what the parts inside look like, with part lines, sprues, rough finish, etc hiding in there on near every part today....why buy that when I can buy an older nicer-made gun of superior materials for LESS money?

[Just Jim]

I believe that MIM parts started in 1989, so if you want a non mim gun then buy before then.

jj

[denfoote]

Just for S's and giggles, I went into my Midway catalog and designed a 1911 using all non MIM parts.
By the time I was done, I was over $1000!!!!
Forged parts are nice, but they are way expensive!!

[Charles Daly]

Joshua,
Where did you hear that Armscor 1911 frames are MIM? From my understanding they have always been cast.

Just curious,
Michael

[mljdeckard]

I have my suspicions, which are really just that.

For many years, 1911s came pretty much in two flavors. G.I. styles and high end custom guns. Then, in the mid 90s, Kimber shoved into the 'semi-custom' market. They showed that a hand-fitted slide does not in fact cost several hundred dollars to produce. All of a sudden, there was a way to have a nice, tight, reliable 1911 without spending over $1-2000 to get it. The 1911 market exploded, and other manufacturers followed suit.

Of course, there still existed 1911 snobs, who had been buying Wilsons, Baers, etc, for years. They were suddenly faced with the stark question, "What is it your $2000 'custom gun' can do that the 'semi'custom' gun can't?" A conundrum indeed. A couple of years ago, I shot a Nighthawk at Impact. Wow. Tight. Gorgeous. Those machined aluminum grips were VERY nice. But it was priced at over $2000 MORE than my Kimber. I was reminded of Vincent Vega in Pulp Fiction. "Wow. That's great. That's the best milkshake I've ever tasted. But it ain't worth $5."

If MIM parts are doomed to fail, all mine must be defective indeed. I'm north of 10k rounds in my Kimber, and I don't even know how many .22s I've shot with the conversion kit, and it is by far the most reliable pistol of any caliber, configuration, or manufacture I have ever owned. It's a pity my sons will never know this, because I think I am going to be buried with it. Other manufacturers I have carried, and had many problems with, (S&W Sigma, Beretta, Tarus, Ruger, Para Ordnance,) would LOVE to make pistols this terrible.

Replace the MIM parts? This is the best pistol I've ever used, I'm not changing a thing. I added night sights, Hogue finger-grips, dropped the full-length guide rod, otherwise it's bone stock. It's my only carry gun, I take it hunting, I would take it to war tomorrow if my command would look the other way. (Which they won't.)

[Golden Hound]

Hahaha, I was reading this the whole time assuming that MIM meant "Made in Mexico," since that's the terminology for Fender guitars. You learn something new every day.

[shootinstudent]

For many years, 1911s came pretty much in two flavors. G.I. styles and high end custom guns. Then, in the mid 90s, Kimber shoved into the 'semi-custom' market. They showed that a hand-fitted slide does not in fact cost several hundred dollars to produce. All of a sudden, there was a way to have a nice, tight, reliable 1911 without spending over $1-2000 to get it. The 1911 market exploded, and other manufacturers followed suit.

You have a lot better luck with the tight frame/slide fit of these new semi-custom guns than I have.

I've seen stock Colts run with zero failures out of the box.

I've seen two SW1911's, one Springfield 1911A1 stainless, and two kimbers go from purchase to range....all had FTF's out of the box.

[Joshua M. Smith]

Where did you hear that Armscor 1911 frames are MIM? From my understanding they have always been cast.

Michael,

There are several people stating this via the Internet. Just run a Google search.

Then again, it may be misinformation that someone posted and the rest just ran with.

I don't remember the source, but I do know that I heard it stated that the slide was forged or cast (don't remember which) and the frame, MIM.

Again, right now I can't confirm it. Mainly 'cause I need to get to bed.

I'll look around some more tomorrow.

Josh <><

[VHinch]

I'm pretty certain that the all the Armscor frames are cast. Not saying they don't exist, but I have never even heard of an MIM frame on a 1911, and running a google search on it only brings up your threads on this topic.

I have seen instances where people don't understand that casting and MIM are not the same process, perhaps that's where this one started?

[Shear_stress]

I have seen instances where people don't understand that casting and MIM are not the same process, perhaps that's where this one started?

Exactly. Seems like there is too much internet rumor mongering and speculation by people who don't know the difference between MIM, investment casting, forging, pressing, machining (which can be used to craft parts straight from billet or used as a finishing operation for cast, pressed, or forged parts), etc to have an informed debate. All forms of manufacturing have strengths and limitations and are all capable of producing high or low quality parts.

[Cesiumsponge]

A lot of people seem to fear new technology. It might be ignorance, or the "back in my day" mentality.

There are still revolver people that scoff at autoloaders. 1911 guys that scoff at Glocks, Glock guys that scoff at Springfield XDs. People that don't like magnified optics and swear real shooters use irons. People that disdain tritium inserts.

The same thing applies when new manufacturing processes have neat names that might be bled into their marketing campaign. Then you got people that claim handmade is better than a CNC center that can hold tolerances of 0.0001". People that claim this type of barrel rifling is better than that type. People that claim stainless is inferior to blued metal. That castings suck, or MIM sucks, or that forging is better than solid billet, or vise versa. That newfangled coatings like gunkote and ceramics are fads and real guns use a hot blue.


If all these people had their way, we'd still be using technology from the 1800's hand filing everything without interchangeability or mass production.

MIM is just another manufacturing process that lends well to firearms manufacturing on a large scale (since initial investments for the forms aren't cheap), but there will always be people resistant to change who will dismiss it as something inferior in their mind. Such is the way of the world.

[rcmodel]

Ruger uses Investment Casting, not MIM Metal Injection Molding.

As a matter of fact, they have a large IC plant / sister company in Prescott that makes parts for many major firearms manufactures as well as aerospace, and automotive industries.
http://www.ruger-firearms.com/Casting/index.html

Don't confuse Investment Casting with oldtime "cast iron", or MIM and such.

It's not even close to the same thing, or strength!

rcmodel

[cktad]

From 1911.org/Armscor/RIA forum:
Armscor/RIA MIM Parts -
slide stop
plunger tube
sear
disconnector
ejector

Frame is investment cast.
Slide is milled out of extrude stock bar (with a cross-section similar to slide).
Barrel is AISI 4140 grade round bar.

[Ala Dan]

Originally posted by: Joshua M. Smith-

"As far as I can tell, only Nighthawk and (maybe) Brown
don't use them"

Well bud, the last time I checked- Les Baer doesn't use 'em either~!

[tekarra]

Gun Slinger,

Good post. Let me add a few points. The process to which you are referring is Powder Metallurgy. Sintering is the process of fusing the powder to make a solid part. Sintering liquefies only the surface of the powder particle to fuse it to the neighbouring particle. If the powder particles melt, the result will be a cast blob of metal. Powder metallurgy is the only process by which the density of a metal part can be made to vary. I guess this might be done with MIM as well, I am just not that familiar with MIM. Depending upon the use of the part, the size of the powder, the pressing force and the sintering time and temperature can be changed to affect the properties of the part. The finer the powder, the higher the pressing force and higher the sintering temperature, the more dense will be the part.

Good shooting.

[Old Fuff]

A lot of people seem to fear new technology. It might be ignorance, or the "back in my day" mentality.

Yup, that's the Old Fuff for you, elderly and dumb. Hardly knows anything. Simply rejects anything that's new out of total ignorence.

But then it might be noted that his experience spans some 60 years plus, with a lot of those working within the firearms industry. Somewhere in there he did learn the differences between various manufacturing methods, and observed that sometimes - just sometimes, manufacturers would turn to alternative ways to make things simply to save money without worrying about quality issues. Anything that would work, at least in the short run, was acceptable to the company bean-counters. :uhoh:

Now it is said that you can fool some people some of the time, and others all of the time, but you can't fool everybody all of the time. I think that applies to the idea that doing it cheaper is better. Occasionally that might be true, but in the meantime the Old Fuff, being stupid as he is, will continue to focus on guns made the old ways.

Anybody want to join me...? ;)

[ieszu]

Having worked with forgings, castings and MIM parts.... I have to say that although MIM seems to be the perfect solution, not all companies do it properly, and thus the quality is rather poor with a low life span. If it is done correctly (very few do) it is as good as older methods, with a cheaper cost base.

The question is one of quality control.... some companies have it, others don't. But with regards to metallurgy, they should be equal so long as they are used for the right parts. I would hate to see a spring (or any other part that flexes) made from MIM.... but a slide or firing pin stop should be just fine....

Just my $.02

[machinisttx]

Occasionally that might be true, but in the meantime the Old Fuff, being stupid as he is, will continue to focus on guns made the old ways.

Anybody want to join me...?

Being a young guy myself, as well as a machinist in the real world, I'm already with you....for the most part anyway.

[rainbowbob]

Anybody want to join me...?

Yes...is it true (as posted earlier) that pre-1989 is pre-MIM? Is there an easy way to tell the difference when looking at a used gun short of running the serial number and learning the date of birth?

[454c]

QUOTE:
"A lot of people seem to fear new technology. It might be ignorance, or the "back in my day" mentality. "


Or they might prefer the best parts that can be built.




Just because something is new doesn't mean it's better. MIM is a cost cutting measure that still keeps "most" customers happy. If manu. thought "most" customers would buy a gun with a 200 round life span at the same price, they'd build it in a heartbeat.

[loop]

Personally, I'll dump any MIM or "whatever-cast" parts I have ASAP.

There are two words that should be pivotal in this conversation that have not been mentioned - brittle and flexible.

Forged metals are more flexible and less brittle than molded or cast metals. If you doubt this then you need to do your homework.

Guns do a lot of twisting. This is one of the most stressful things you can do to a piece of metal. It also hardens the metal more every time it happens. Hardening it means it gets more brittle and, therefore, closer to failure.

MIM and cast parts are at the edge in terms of being brittle when they come out of the box. Ever try to "tune" a cast part? It's called breakage.

I may take a frame that is cast or molded, but that is only because you can replace a frame cheap. OTOH, if it is a forged frame you won't need to replace it.

I finished building a 1911 about three hours ago. It does not have a single MIM or cast part in it. Yeah, it cost about $750 (for me to build). And, BTW, it will cost most folks about 2K to buy.

Every metal part is forged. That is because that is what can be bent, filed, milled, twisted and tweaked without losing integrity.

If MIM and casting are so great why aren't springs made that way?

They aren't made that way because they are brittle and lack flexibility.

IOW, they lack durability.

It may take 100 years for us to find out just where they actually fall on the scale of durability, but I have forged guns that are 100 years old that I shoot anytime I want. If I own any guns with cast or MIM parts I wish someone would point them out to me so I could get rid of them and replace the guns or their parts with something that is made with some quality.

Of course that would not be possible. I have at least 50 guns I've never even shot.

Oh for the old days. You'd fit your slide to your frame by clamping it in a vise and squeezing it bit-by-bit until the slide to frame fit was tight. Try that with your Ruger and you'll be ordering a new slide.

Of course, we don't have mechanics anymore. All we have is part replacers.

XDs and Glocks must have JMB turning over in his grave.

[rainbowbob]

Can anybody tell me how to determine whether a used firearm is made of MIM or forged parts?

[fletcher]

^ Short of chopping it up and etching it, I don't know of any non-destructive way to tell the difference.

If MIM and casting are so great why aren't springs made that way?
It would be extremely expensive, inefficient, and would not produce the desired properties to simply cast or MIM a spring - one unsuitable application is not sufficient to question the quality/role of MIM or casting. Forging would also be a poor choice for spring-making. Extrusion/drawing is where it's at for this application.


Forged metals are more flexible and less brittle than molded or cast metals
That's not entirely accurate. Forged metals offer an advantage due to closing internal voids (greater density, higher internal quality) and creating directional strength from flow. Cast metals can be both more or less brittle than a forged part, it's all dependent on processing.

[rainbowbob]

Short of chopping it up and etching it, I don't know of any non-destructive way to tell the difference.

JustJim opined that anything built before 1989 would not include MIM parts. Can anyone confirm and/or elaborate on this?

Old Fuff?

[Drgong]

MIM was only developed in the 1990s if I recall, so 1989 should be MIM free.


To make it simple on all the folks this is a laymans guide to metal forming options used in guns.


a Forged part is heated to near melting tempture of the metal, and then hammered into shape by machine. metal has a chystal structure (think like wood grain) and the forging process can use that structure to make a stronger metal object.

Casting is when one pours molten metal into a mold and it is allowed to cool. Sand Casting is one of the most simple ways of casting (metal is poured into mold made out of sand) and investment casting is a more complex method where complete molds are produced and metal is cast from these parts.

Powder Metallurgy (Most famous being ZAMAK based alloys) which come in powder form and can be melted at lower temptures then normal steels. however the "interconnection" of the metal is not the same as a single bar of metal, and this type of metal was used for years to make such guns as the Raven.

Metal injection molding is very similer to Plastic injection molding, allows for tight tolerances. I would say that its not been around long enough to know if it breaks too early or not.

sorry for any mispellings...

[Old Fuff]

Rainbowbob:

The Old Fuff has decided to charge $200,000.00 per answer because his friends have told him he'll get what he has com'min... :what: :D

Anyway. The S&W 686 went to MIM Lockwork in 1998 at 686-5.

The easy way to tell: With few exceptions (such as rimfire revolvers) the firing pin will be mounted on the hammer in pre-MIM revolvers; and MIM triggers are hollow on the back where earlier triggers are solid.

Some revolvers had mixed parts for a short period, so you might find a revolver with an MIM trigger but conventional hammer, or perhaps the other way around.

[Cesiumsponge]

MIM did not exist 60 years ago. Neither did CNC and a host of other technologies today that have gotten us into outer space. To claim that we have nothing today in this world that can beat 100-year old technology is a bit presumptuous...kind of like katana fanboys that claim nothing in the universe can beat the sharpness of a 400 year old sword made by hammering a lump of iron.

Old-world craftsmanship is one thing (and something I respect), but claiming every new innovation is somehow the downfall of society sounds alarmist. As mentioned, without innovation, we'd have no parts interchangeability. We'd still be hand-fitting each individual part on an individual gun and costs would be astronomical with today's union-driven labor prices. If you look at the history of firearms, parts interchangeability played a huge role in making firearms more practical to manufacture on a large scale and dropped price to make it more affordable. I like the security of forged and billet parts too, but on low-stress items, it does not really matter much...not to mention the manufacturing industry base in the US has been vanishing for decades so we are loosing the machinery and skill to manufacture efficiently. Most of the cutting-edge manufacturing technology comes out of Japan now.

There are plenty of cost-cutting measures, but it doesn't necessarily mean you're dropping quality because you pump up quantity. Some costs are associated to inefficiency and fat that can be trimmed. If you're simply axing corners to save a buck without maintaining or improving the product quality, then you're guilty of creating a bad product and your argument comes into play. Poorly, cheaply made products are worthless.

If you're going to argue we're better off having people in machine shops run Bridgeports and engine lathes instead of multi-axis swiss machines and palletized machining centers, then I'm going to have to disagree.

Anyhow I work in aerospace manufacturing but that doesn't mean I'm some tech geek that hates "old stuff". I know how to hand scrape, something perfected over 100 years ago and rarely practice today. I doubt you'll find any machinist today that knows, let alone heard of the process. There are few people capable of creating bearing surfaces flat to .00005" (50 millionths) with nothing more than three plates of iron, and old file, and knowhow. Not even modern machines can fit precision metal surfaces together like that, especially rebuilding machinery. A time and place for every process.

If MIM and casting are so great why aren't springs made that way?

If springs are so great, why aren't engine blocks made of spring steel instead of castings?

Its easy to jump to baseless "arguments". Every manufacturing process has it's place. Sometimes doing things the "old way" is too labor intensive and not practical because the market won't support it. I see so many threads on THR about how ammo is so expensive and guns are so expensive. If we made everything with 50-year old technology and methods with today's labor rates and economy, boy 80% of the THR posts would be complaints about why a forged Lorcin costs $600 even if they might be superior to stamped Lorcins coming out the parts bin into a delivery truck for $149. The commercial plane you fly in has lots of titanium and stainless steels sourced directly from China; I've seen the material certifications myself, and those jumbo jets are full of cast parts too. Food for thought.

[Clean97GTI]

and correct me if I'm wrong here, but the failure of a MIM part would have a lot more to do with its heat treatment rather than the structure of the metal itself (assuing no hidden defects)
Basically as long as its prepared properly, you should get long life from it.

[rainbowbob]

Old Fuff:

The check is in the mail. But for that kind of money I have to ask another question...

...the firing pin will be mounted on the hammer in pre-MIM revolvers...

What do you mean by that? Is the firing pin molded with the hammer in a MIM part?

MIM triggers are hollow on the back where earlier triggers are solid.

That does sound like an easy way to identify MIM.

This is an interesting discussion about the various metallurgy techniques and evolving technologies.

Speaking of old school...I just saw a show on the History Channel about ancient Greek metallurgy. They had armor and weapons made in ingenious ways that they said can NOT be duplicated today! I don't understand how we couldn't at least reverse-engineer anything they were capable of - but that was the claim.

[Cesiumsponge]

Its difficult to reverse engineer stuff when the process is incredibly convoluted and "lost in time". They still can't figure out Greek Fire, and they aren't exactly sure of the forging methods used in many western damascus, Wootz damascus, or damascus-like steel even though most high end modern knifesmiths are forging their own damascus stuff.

I give a lot of credits to our ancestors. They aren't really different than us. They were equally ingenious

MIM parts often have ejector pin markings, flashing, or part lines but these are usually kept to a minimum and possible deburring afterwards would remove traces of such.

[machinisttx]

MIM parts often have ejector pin markings, flashing, or part lines but these are usually kept to a minimum and possible deburring afterwards would remove traces of such.

It does remove the flash, and I've yet to see any parting lines, but it does not remove the ejector pin markings--at least not on the MIM gun parts I've seen so far.

[Clean97GTI]

rainbowbob, on older S&W revolvers, the firing pin was pinned onto the hammer. When the hammer dropped, the firing pin went through a channel and hit the primer. It wa a forged piece of steel that made the gun run. In fact, my grandfather carried a S&W model 19 that I hope to inherit one day.

Later models don't do this.

[Old Fuff]

The check is in the mail.

I can hardly wait, but the tax collector will be with the mailman... :D

What do you mean by that? Is the firing pin molded with the hammer in a MIM part?

There are some exceptions, such as .22 RF revolvers, but most pre-MIM Smith & Wesson and Colt double-action's have a separate firing pin mounted on the top/front of the hammer and held by a rivet. MIM guns have the firing pin mounted in the frame. If you cock the hammer and look at it you will either see, or not see, a firing pin. Also most (but not all) revolvers with MIM parts also have the lock mounted above the cylinder latch thumb piece.

[fletcher]

Just in case anyone cares to learn a little more about MIM, pages 1-10 of this book (viewable online) describe the process:

http://books.google.com/books?id=-Hv50lh-7Y4C&printsec=frontcover&source=gbs_summary_r&cad=0#PPA1,M1

[blkbrd666]

To add to drgong's definitions...I believe MIM, although still "casting", is more between casting and forging. Rather than taking metal to a completely liquid state and pouring into a mold, MIM usually takes metal to a semi-solid/semi-liquid state and it is then inserted into the mold using pressure/counter pressure(pressure at one point and a vacuum on the other end). The advantage here over casting is the semi-solid metal is less likely to have voids due to the process(pressure) and less cooling time. Most of the cost savings are due only to less time from solid to semi-solid to cooled solid again. So, because it's cheaper doesn't necessarily mean it's lower quality, it's just a technology advancement over traditional casting to get metal into the shape desired.

I could be completely wrong...I make no warranty on the above spillage. I'm just a computer geek who works for an iron foundry corporation.

[fletcher]

^ Yes, MIM/sintering never reaches melting temperatures, but instead relies on diffusion to achieve a high density. At the high, but sub-melting, temperature, the atoms are more active and will flow into the voids and remove them.

[rainbowbob]

MIM guns have the firing pin mounted in the frame. If you cock the hammer and look at it you will either see, or not see, a firing pin.

I did not know that. Thanks, Old Fuff - that clears it up.

[Old Fuff]

I did not know that. Thanks, Old Fuff - that clears it up.

Good! But remember that any rule can be broken. There are some older models that have frame-mounted firing pins but older "real steel" lockwork.

Another tip off is that MIM hammers are hollowed out on the sides on the inside where it is hardly visible. Older hammers on solid on the sides.

MIM parts have a sort of "pebble-like" surface. Older parts are much smoother.