I am sick and tired of reading all the back and forth between MIM and machined parts. Guy A says “MIM has greatly improved and is every bit as good as a machined part” while Guy B says “MIM will break on you, do not use it on a duty weapon”… after many days and hours spent researching the subject - I’ve been unable to find any actual scientific testing that shows any strength/wear property discrepancies between the two manufacturing processes. It wouldn’t be that expensive - just buy a small selection of MIM and machined parts, run them through batteries of tests, starting with the least destructive first, and then measure at what force or # of cycles it takes to destroy the part. Then a simple chart could be made showing definitively once and for all if MIM is that much weaker - and by how much. If I had the time and money I would happily perform these experiments. I have a ton of ideas about how the tests could be done. A week or two worth of research would end the MIM vs machined debate once and for all. Of course, to be fair, a few samples of each part must be used. Anyone with an adequate arbor press, some spare 1911 parts, and some extra time could contribute at least some valuable data. Why has no one done this? Or have I just not been able to find the link?
Who cares? Is it really that big of a deal? Buy from a reputable manufacturer and it shouldn’t really matter. I honestly have no idea what parts of my CRG are MIM and what aren’t, and could care less.
Very old and totally debated out topic. Neither side of the argument has proven to be correct. Not worth opening another thread over the matter.
I care to an extent… any radically new manufacturing process takes many many years to perfect… Machining is a well-established process - MIM is not. I do know that I have guns from the 50’s that have only had to have springs replaced on them and still work and look almost new.
MIM is a huge cost-savings measure - we all know that. But what we don’t know is how these parts compare to machined parts. I just don’t see how it could be as structurally stable. I mean, a polymerized wax-like substance added to powdered metal and then squirted into a mold - that comes out in a form that’s ~30% larger than the finished part, and can be broken apart by HAND. Then further heat treated to produce controlled shrinkage??? I see so many variables for failure…
I just noticed that it’s been a topic of much debate for quite a while and wonder why no one has done any scientifically-controlled testing on these MIM parts. All I ever get in response is “It’s 98-99% as dense as cast material” or some other nonsense.
I do care, because guns used to work out of the box and they just didn’t break as often. I want legitimate answers since the industry is going to MIM and we could all suffer from it.
EDIT: I’ve been buying guns with my dad since the 80s and we never had to return a new gun for warranty issues - just in the past year I’ve had to send a Sig P238 in for a broken trigger and a Northtech Defense lower in for being out of spec. I’m just saying… (I know the lower has nothing to do with MIM)… Guns ain’t what they used to be…
EDIT EDIT: If there’s no difference, would you buy a MIM lower receiver? Upper? A MIM bolt??
EDIT EDIT EDIT: I know it’s been brought up before, but how hard is it for people to run controlled independent tests to show the difference in strength and failure method between MIM and machined parts - that’s all I was getting at. All I can find is conjecture and third-hand accounts…
I did a trigger job on MIM parts in my Springfield, it came out really nice and is holding up very well, 2 1/2 #'s of powder worth of reloads since.
I asked a well known 1911 smith about it and he said just keep an eye on it but probably no abnormal problem will pop up.
I won’t say its top quality stuff but it’s seems to not be total crap either.
I traded that Pistol smith a fly casting lesson for some top quality parts, I should fit them, do a trigger job and see what my results are but I think I’ll wait and see how long the MIM parts last.
Wait until 1911 parts are made by 3D Printing.
I mean nothing burns off completely without leaving byproducts behind - even if only carbon. I imagine that there must be tons of micro-pores full of this unburned-off waste material in MIM parts… I don’t see how it could be otherwise… Surely that would make for a weaker material… and I hear you about the 3D printing. Hey, it might be neat to order a part off of Brownell’s and print it directly instead of waiting for it to be delivered. I’m getting off topic though… I have a ton of MIM parts that I wouldn’t mind destroying in the name of science but all the machined stuff I have is Wilson Bulletproof and I don’t feel like destroying those… Anyone have any machined 1911 parts that they want to donate in the name of science?
fwiw:
Fitment & Quality of either determine long term usability. . . . Fit it right: not loose or extremely tight, keep it wet & it will function day or night
It was a Sig! What is there to debate? They stopped making good Sigs eight years ago.
Ruger has used MIM frames for 30 years. My service six is still running strong after 20 years of a tough diet of 357 mag.
Buy once cry once.
Not true… they had some initial hiccups when they moved to Exeter, but I wouldn’t put their lemon rate at a higher level than any other current manufacturer… and in Sig’s defense, they had the gun back to my house in six days with a dreamy 5 lb trigger (came from factory with a completely random 7-15 lb trigger) and it didn’t cost me a dime. It took me all of about 3 minutes on the phone with their customer service from the time I dialed until the time the call was over. But anyway… that’s interesting about the MIM frames on Rugers. I only like their .22s and SA revolvers anyway. I’m not trying to bash MIM, I just want to see some hard data… It would be easy enough… an example of a test: Use an automatic center punch on equivalent MIM and machined parts - then measure the depth and width of the indentation left. There’s a million more tests. It really seems like gun quality as a whole has dropped dramatically and I wonder if there’s a correlation to the new manufacturing methods being used to save money.
A MIM part could still be 95% as good as a machined part, but the 5% that fail, that wouldn’t have if they were machined, would cost little to the gun manufacturer to repair as opposed to the huge amount of money that they’re saving by using MIM in the first place. Factor into that the home gunsmiths who will not even send their gun in and just replace the part themselves. I just don’t want the wool
pulled over our eyes - why is it so hard to find material data on the differences between MIM and machined steel parts?
I won’t debate Sig quality. I quit watching Sig when they started releasing rainbow colored guns.
MIM has been around a long time. Each company weights the cost of using MIM parts. It’s cost effective to use MIM parts in their guns. We no longer have 50 to 80 gun companies, we have 1000 plus producing guns and selling parts, quality will go down with high demand.
The old adage is still true. Buy once cry once. Seek out the companies that care and you have a much lower chance of getting a bad part.
Ruger has never used MIM frames or slides. The parts are investment cast
You are correct, excuse me. Investment cast. The point is they are still cast. Cast parts can be very tough.
Production guns are all built to a spec and a price point. There is a reason the safety lever on an M4 isn’t made of Carpenter 158 or ASTM 53100. An engineers ability to design parts using new materials and methods has gotten much easier with FEA and 3D CAD. Is MIM the best? I don’t know. Is it good enough? The product liability attorneys must think so.
When said “lab test” is performed come back and post results.
Otherwise this is and will be just another “MIM” thread.
…and that’s why no one knows… Because there hasn’t been any independent testing done. We’re left at the mercy of what gun manufacturers and MIM machine makers tell us. I have the equipment and ideas for running batteries of tests, just not the funds right now to purchase a large sample of MIM and machined parts to run them through. On knife forums, there’s always someone with more money and guts than brains, willing to destroy a $400 knife in an effort to educate prospective buyers - this seems like a more serious issue as it affects almost all guns being currently made - not to mention, the cost to run such an experiment would be minimal. There would be no more MIM threads if we could figure out once and for all if and how they’re inferior. It’s not like a lab would be needed.
Investment cast products can & very often do contain voids within the material. It takes a significant amount of work to minimize casting voids.
A casting void is essentially an air pocket or bubble in the liquid metal. If the pour into the mould is done improperly, small air pockets can form as the metal cools. These, of course, can make the product weaker than forged steel.
Steel forging uses hammers and pressure to drive out the air pockets and form the metal into a cohesive piece. This is not done on investment cast parts. This is one reason some parts of a Ruger (e.g. topstrap) are thicker than on Colt, S&W and other forged metal frames.
MIM uses a powdered metal blended with a polymer. This is injected into an oversized mould (oversized for the finished part). This “green” part is then heated to drive off the polymer and fuse the metal together in a process called sintering. During the heating process, the part shrinks predictably and tolerances of the finished part often require no secondary machining steps. MIM is especially good for smaller parts with complex shapes that would normally require several machining steps.
MIM reportedly is around 98% as dense as wrought iron so it is better than investment casting for strength in small parts. Tensile strength of properly treated MIM parts is close to that of mill forged steel.
If you are looking for independent testing, I’d suggest Metal Powder Report. There are also a number of medical and aerospace powdered metal injection part studies to be found if you do a simple “googlescholar” search. For example, studies like this are prevalent: http://www.sciencedirect.com/science/article/pii/S0924013606008983
To put a fine point on it, just like every other metal fabrication process, the skill/expertise of the team doing the work means significantly more than the process used. You really can’t lump a process like MIM as good or bad. It entirely depends on how it was done.
Thanks for the link, but you have to buy $30 PDFs to get the whole story. The particular link you sent me covered the ideal metal/polymer ratio for MIM… that’s it…
…and 98% as dense as wrought iron - when was the last time wrought iron has been used in a firearm, 1886?
The link wasn’t intended to provide you with a quick, authoritative good or bad for guns answer. Good or bad is up to the educated end user.
Also, the abstract gives one a feel for the amount of variables at play.
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