MIM or Forged Parts

Well anyone who has been a fan or owns a 1911 knows about Metal Injection Mold parts. MIM stands for Metal Injection Molded. In a cast part the metal would be poured and then sets up by itself. Its is very common place to find said parts in not just 1911 but almost all guns.
In Injection molding the molten metal is pressed into a mold at high pressure and then it sets inside the mold under pressure until it is of the strength specified to produce the given part. The grain structure is also controlled by the amount of pressure, usually in 10's of ton's per Sq. In. The pressures cause crystalline structure alignment of the atoms. It is the same process as most any plastic injection molded part..

Also, a big factor is the application for the MIM parts. Colt used MIM extractors in their 1911's until they found that this cost saving measure was not saving them money because of all the repairs they were doing on replacing the extractors under warranty. They stopped using MIM extractors but still use MIM parts for the mag release latch, sear, and some other parts. MIM parts can give you a very nice, smooth trigger as they are hard.

It is true that the most important factor with MIM parts is application of those parts (fine in ultra high speed jet turbine blades which do not flex but very poor application in firearm extractors which do flex-something Colt learned the hard/expensive((as in warranty repairs)) and the quality of the manufacturing process (questionable from a third world company).


So what do you prefer or what are your thoughts on this. If given the ability I would change all MIM part on my weapons to forged/machined from billet. I feel better knowing I have the strongest parts available, its just one less thing that could go wrong and it gives me piece of mind. I just like 100% metal machined parts.

There is not an option for "Am totally ignorant on this subject and look forward to reading the posts in this thread so I can learn as much as I did from the OP."

That's my vote.

eye95 said:

There is not an option for "Am totally ignorant on this subject and look forward to reading the posts in this thread so I can learn as much as I did from the OP."

That's my vote.

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Yeah, that definitely needs to be an option. It would already have at least two votes.

sultan62 said:

Yeah, that definitely needs to be an option. It would already have at least two votes.

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I have other is set as see post for this very reason, there is so many other options that would make the poll too big, So I tryied to make it as small as possible.

Oh, OK. I took it as injected, cast, forged, or other method of forming the part.

I'll check other. I'm still interested in the technical stuff that more knowledgeable people than I are going to post.

To help give unfamiliar people a little more insight on the matter of the three main types of part you do see.

MIM=metal injection molded. Different from cast, which is machined, as is forged. MIM forces a blend of metal powder and glue into the mold. Then the part is taken out and "fired" to bond the metal into a solid part. Typically in a high quality controlled plant it can be at a range from 90 - 95% as dense as forged steel parts. MIM is probably better than cast in most respects. MIM can typically be made to specs which are tight enough that additional machining is not required. That is why so many company's uses MIM to save overhead. Here is where it gets messy, if the process is not tightly controlled you can have a wide difference in density of the end product. In short a part that would have done well with a density of 92 or better, but due to poor quality control the parts can be around 85 for example or worse.

You take a much higher chance to have a product break with cheap quality MIM parts verses a forged part.. So if given the choice i will chose a forged part every time, it may seem silly but its one way I knock down the % of the possibility of having a weapon fail me.

Is the hate in some cases fair against MIM, yes and no. A product from a that has a very high quality control you get a very close product to a forged piece, in turn save money. If factorys that dont you run the risk of that part breaking when you need it the most.


CAST is made by pouring hot molten metal into a mold and letting it cool. Usually the density can get as low as 60% of a forged part (much lower strength). Yet here is the kicker. One plus to cast, per pistol makers, is that you can harden it to a much higher Rockwell than a forged piece. That's the reason FN went to a cast vice forged slide in the Hi-Power.

Yes, injection molding of a plastic binder with metal particles. The binder is dissolved and the part sintered, for nearly the same density +/-3% as forged but with high accuracy in complex small parts.

On the STI web site there is an article written by an engineer/metallurgist who says MIM gets a bad rap and in some circumstances it is fine, Interesting read

swinokur said:

On the STI web site there is an article written by an engineer/metallurgist who says MIM gets a bad rap and in some circumstances it is fine, Interesting read

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Agreed and like I said it’s not a deal break for me to buy a firearm with MIM parts. I just prefer and will spend money to make my firearm a only forged piece because it is a stronger density material. There are a number of gun manufactures who have many of the parts mass produced in country s like Mexico for example who are known for making less than quality products. Some of these company's do not have the same high standards of quality as those who hire them to make the parts. I just don't like rolling the dice on a part that may/ may not have followed the correct process to produce a strong mim part. Because the density of the parts are almost never the same across the board. Again MIM will never be 100% the same density of a forged part, it can be close but it cannot be guaranteed. The little of the wrong changes in the process can make HUGE difference in the density of the product and with them be mass produced you would never know.

Forged metals tend to be harder, stronger and more durable than cast forms or machined parts and mold injected parts. The reason why is simple: pressure alone forms the steel into the right shape and the metal's response to such overwhelming force tends to align the grain. That means you get more cogent internal structure and a far greater ability to withstand warping and wearing. There is a reason forged products are so much more coveted than cast or machined metals and mold inject metals. Forging is a unique process that tends to imbue the final product with uncommon strength--the inevitable result of being pounded, pressed, rolled or upset into an existing form. Metals that have undergone this powerful process tend to come out much stronger, harder and more durable than their cast counterparts or MIM parts

Forged products in many cases ten to command higher fees than their die-cast counterparts because of the greater strength and durability they exhibit. Heating and forging steel tends to create an even grain in such a way that the resulting part simply lasts longer than anything poured and molded.

I didn't know about all this until AFTER I bought my 1911. I have a Dan Wesson Bobtail Commander, and I assume, knowing what I paid for it, that it is at least partially forged. It is stailnless steel, so I assume it was machined but I may be wrong.

Ruby said:

I didn't know about all this until AFTER I bought my 1911. I have a Dan Wesson Bobtail Commander, and I assume, knowing what I paid for it, that it is at least partially forged. It is stailnless steel, so I assume it was machined but I may be wrong.

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You can call most companies and will give you a list of mim part, I was able to get Springfield to give me the list while my friend who owns a kimber could not get any list. Yet they where willing to put all forged parts in for a price.