MIM parts and rust ?

[NeroM]

Was frustrated by the high prices for some vintage S&W revolvers, eg. M10 and M25.
Often the cost of a vintage specimen in good+ condition was similar to new "classic" units.
I've purchased Classic M10 and M25 revolvers amidst the feedback about MIM parts and the hole, etc, etc. Have also posted about how good these new units are - fit, finish and function are and have been great - no need to tweak these units.
Rotate M10, M25 and a FA83 as my daily walking around woods carry firearms, carry them in a chest holster on top of what every layers of clothing are needed - also have been out in all weather conditions -so they have often come back snow/ice covered, we from rain, a few days recently was about the back40 with temps well below zero. When back in the basement - right away wipe each gun off with a cloth - if really wet- might spritz it with a little WD40 and dry it off [often in front of a fan]
Just recently, cleaning the M10 after a real snowy walkabout - I noticed back of the trigger appeared to be rusty [pic below] - the back is sort of a trough - could easily hold a drop of snow/ice/water. Was able to easily rub the rust off with a swab and a tiny tuft of superfine steelwool.
So, are MIM parts more susceptible to rust, than traditional forged/machined parts ?
Anyone else with a similar experience ?
Thanks,
Nero

 

[Pat Riot]

I have not, but I have not had the opportunity to expose my guns with MIM parts to those conditions. My 327 NG has experienced rain and wetness in the Oregon woods but I had no rust issues.

 

[mcb]

It going to be more dependent on the material than whether it's MIM or not. A 10XX series steel its going to be significantly more prone to rust than 4XX series stainless steel independent of whether its cast, billet, or MIM'ed, for an extreme example. Depending on the particular MIM processing and post MIM processing (HIP, machining, surface finish etc) a MIM part might be slightly more prone to rust than a billet of the same material due to the porosity of some of the lower cost MIM processes. That said in all but the poorest version of MIM this difference is going to be relatively small.

 

[Riomouse911]

^^ That’s it in a nutshell. Well put .

Stay safe.

 

[halfmoonclip]

The real deal with stainless guns were the older ones with forged, hardchromed works. A buddy had an early M60 that was subject to a roof leak; it was drenched, and stayed drenched, for some considerable time.
I took it down for him; the rebound slide spring had a little surface rust, period.
If the OP really wants something rust proof, those older Smiths are the answer.
As regards the current MIM, I've sweated on a 640 Pro and not noticed any problem on the MIM trigger.
MCB is no doubt correct in his analysis.
BTW, buddy stored a stainless Ruger in a leather holster, and it rusted to the point of leaving pits.
Moon

 

[Riomouse911]

The real deal with stainless guns were the older ones with forged, hardchromed works. A buddy had an early M60 that was subject to a roof leak; it was drenched, and stayed drenched, for some considerable time.
I took it down for him; the rebound slide spring had a little surface rust, period.
If the OP really wants something rust proof, those older Smiths are the answer.
As regards the current MIM, I've sweated on a 640 Pro and not noticed any problem on the MIM trigger.
MCB is no doubt correct in his analysis.
BTW, buddy stored a stainless Ruger in a leather holster, and it rusted to the point of leaving pits.
Moon

Some leather holsters can be brutal on guns left in them for long periods. I lost some bluing off the muzzle of my 2.5” Model 19 because it sat in a Galco shoulder rig for too long.

Stay safe.

 

[edwardware]

So, are MIM parts more susceptible to rust. . .

One of the benefits of MIM is that the alloy can be easily tuned almost infinitely. . . it's just proportioned powder. There's nothing that necessitates that MIM be more or less resistant than forged. Either part could be made from hundreds of alloys.

 

[Master Blaster]

The stainless steel used in a revolver is much lower in chrome content than a frying pan or other stainless items. So it's possible for Stain -less to stain or rust some under adverse conditions.
Some folks might also use a bit of salt in icy conditions that could get splashed around.