Metal Stuff: Cast Forged MIM Stamped Milled...

[Nightcrawler]

Okay, can somebody clear all of this up for me, please?

What, exactly, is the difference between gun parts/receivers that are:

-Cast vs. Forged

-Stamped vs. Milled (I think this is AKs only)

-MIM vs. whatever

I know about the AKs being stamped or milled, but others probably don't. Dont' know if they're forged or cast, though.

What's the big deal about forged parts? The way people here talk, a brand new cast M1A receiver made with modern metallurgy is weaker than a 50+ year old forged M1 Garand receiver. Same with 1911 clone parts. Is this the case? Is old forging better than new casting?

What exactly is metal injection molding (MIM)? I"ve heard people suggest it's not even real steel, and that MIM parts (on pistols) are prone to breakage.

Can somebody clear all of this up for me? Thanks.

 

[Harry Tuttle]

google is your friend:
http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=forging+strength+casting

http://www.qcforge.com/benefit1.html

http://www.forging.org/facts/faq3.htm

 

[Sean Smith]

Greatly simplified answers:

-Cast vs. Forged

Easy. A cast part is made by pouring molten metal into a mold that has the general shape of the part. A forged part is made from a piece of steel that is heated, then hammered into shape. In both cases the raw casting/forging needs to be machined into the final shape.

Forged parts are more dense than cast parts, hence stronger when the parts are of equal dimensions, but more expensive to make.

-Stamped vs. Milled (I think this is AKs only)

A stamped part is, well, a sheet of steel that is stamped into shape. A milled part starts as a solid piece of steel that is milled into shape.

-MIM vs. whatever

MIM is Metal Injection Molding. Metal bits are mixed with plastic, melted & injected into a mold that is close to the exact shape of the desired part. MIM parts are cheap and very hard, but tend to be brittle, and the MIM process can produce internal defects that aren't apparent until the part breaks in two for no apparent reason.

Note that these comparisons assume that the same steel alloys are being compared. With a better alloy, a cast part may be stronger than most forged parts, for instance.

 

[Nightcrawler]

So.

Is all the hooplah over Springfield Armory's cast M1A receivers really founded in something? Are GI M14 receivers made in the 50s stronger? What about M1 Garand receivers made in the 40s?

 

[Nightcrawler]

Bump.

Anyone? Cast vs. Forged?

 

[daniel (australia)]

Casting n metallurgy: an agglomeration of cracks, cold shuts, inclusions and porosity, more or less held together by welding and blind faith...

 

[DBR]

Properly made castings can be more than equal to forgings. Forgings also suffer from: cold laps, inclusions, stress cracks, hard spots, grain defects, etc. Casting technology has come a long way from the early 1900s. Some of the best alloys on the planet start out as castings (billets). With modern techniques it is probably easier to control the final properties of a casting than a forging.

 

[Sydwaiz]

And then there is Die Cast...

Bryco
Phoenix
Davis
Jennings
Lorcin
etc.

 

[cracked butt]

Is all the hooplah over Springfield Armory's cast M1A receivers really founded in something? Are GI M14 receivers made in the 50s stronger? What about M1 Garand receivers made in the 40s?

SA receivers are investment casted, which is probably the srongest and most consistant method of casting metal. They aren't quite as strong as a GI receiver, but the point is pretty much moot as GI receivers are way overbuilt. Ruger makes alot of their guns using the same process. I'm sure if breakage of investment cast parts happens in all but the the rareset cases, you would hear it all over the internet along with the Glock KB's and MIM part breakages.

I hope someone will correct me if I'm wrong about this, but I've read about early Garand receivers being too hard, the heel of the receiver cracking with repeated beating from the bolt. To prevent breakage, they would dip the heels of the receiver in molten lead to anneal them.