Why do the MIM triggers have the cut out area behind them? I assume this has something to do with the MIM process. I’m just curious why it is there. Why didn’t they just take a perfectly fitted forged hammer and use it as the guide for what set the mold? I understand the MIM process allows for some very precise parts to be fabricated with a bare minimum of milling afterwards so why the skeletal look? It seems like if they were solid and then flash chromed they would look that much better and be that much more corrosion resistant. What gives?

The only thing I can think of is the reduction in material used. While on a single trigger it doesn't amount to much, on several hundred thousand triggers it will. Cost per unit is cost per unit.

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H Richard
SWCA1967 SWHF244

I think it may have to do with the mold and making sure the metal slury is injected into ever nook and cranny of the mold. Metal savings would be another possibility.

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Dick

Thanks Guys, best answers and to the point without downing the product. Hat off to you .

Dick is getting close to it. The molds are designed to control flow and curing of the material, very much like polymer injection molding. Very thick sections are easier to fill, but may lead to warpage because the cure is slower. Post-injection compaction also plays a part in MIM. So consideration of warpage, cycle time, shape consistency, and material use is an engineering compromise for each part. That's probably why the trigger is constructed with the slot in it.

I strongly suspect that if S&W could have made the part look exactly like a pre-MIM trigger, they would have done so.

Buck

That is more telling than the reality of the technology involved. I like that part of the answer best since it raises the eyebrow the most...

On a related note, brand new Ruger SP101's also have a MIM hollow back trigger. Over on the Ruger forum some new SP101 buyers are asking "Why does my SP101 trigger have a hollow in the back of it??!" The answer is it's a MIM part.

I don't think it's possible to make a solid looking MIM trigger. if someone were so inclined I suppose you could fill it in with JB Weld or solder and sand it to a flush appearance, then cold blue it to look closer to the case color.

Some new S&W owners use the hollow of the MIM trigger to add their own trigger stops.......there's no end to American ingenuity

Like was said above, if they could have made it solid, they would. The S&W hammers also have hollows in them, you just can't see it as much because the frame hides them.

whats interesting about MIM is the part is actually molded a good bit larger than the final dimension, and during curing it shrinks at a controlled rate to the precise final size

so in order to control the shrinking process it probably cant have large sections of metal or it wouldnt shrink equally in all dimensions (does that make sense)

Uniform wall thicknesses are critical in manufacturing plastic injection molding parts and metal injection molding parts. That is one of the reasons that the MIM trigger appears hollow underneath. Even though it is hollow, the tensile strength of the trigger is greater than your finger, thus, you will probably never break the trigger.