?'s about STI pistols

[titandriver]

Can anyone tell me what year STI started using MIM parts -- if in fact they do -- in their Open pistols? I bought an Edge a few years ago and the thumb safeties lasted only a couple of weeks before snapping into pieces. What parts would typically be MIM?

Thanks!

Rich

[fastarget]

The thumb safety breaking has happened often on STI's I am not sure why.

No issues with our stock Eagle so far, the other two guns have the ed brown safeties which seems like a popular upgrade.

I am almost certain that not all but most thumb safeties out there are MIM, however some tool steel or machined safeties can be had from EGW, Wilson, Nighthawk to name a few.

There will be Better info from our resident smiths'.....

[blaster113]

broke the two stock ambi safeties on two different STI Limited guns, also the tab of the grip safeties. I think for sure those parts are MIM. Parts broke with less than 5k rounds on the odometer on both.

[10ring]

STI did a redesign on their Thumb Safety a couple years ago. Hopefully this has taken care of the frequent breakage.

[bountyhunter]

If the part in question is MIM, you should be able to see ut by looking closely. It came from a mold, so it will have mold lines somewhere like a cast piece. You may also see small holes which are where the material is forced into the mold and where air escapes.

MIM is a TERRIBLE choice for any part which is long and thin and subject to extreme torque. A safety lever should be tool steel as should the extractor or any other long and thin part. The reason is that the primary defects inherent in the MIM process are:

1) Non uniformity of grain size in the metal particles.

2) Air voids (bubbles)

These can and do cause weaknesses. On a thin part subject to a lot of stress, it will fracture at the weak point. On larger parts like the triggers and hammers on SW guns, I have never heard of an MIM induced failure.

However, it's also possible to make tool steel parts that break by over hardening or using poor quality material.

Edited September 4, 2011 by bountyhunter