Here I go again! STI says that their 4" barrel officer pistol in 40 S&W can be converted to 10mm, and that's great, but since I want to push the envelope, I've inquired as to whether their Tactical 3" 40 S&W will work as well. Now that would be a small enough 1911 for even picky me to carry. ;D After STI gets off the floor from laughing, I really hope they say it's possible. Their guns are very stout, so I would have no concerns of safety issues. Excessive wear could be a problem if I go crazy with Underwood or Corbon, etc, but like my S&W CS40 conversion to 10mm, I would limit the hot stuff. So why not just shoot 40 S&W? Because it wouldn't be as entertaining on this 10mm Forum, for cryin' out loud! LOL
Get a second barrel fitted and ream it. Flat bottom firing pin stop and 22-24lb recoil spring and you should be GTG.
I love STI. They actually respond like they didn't have a full time job sweating over warranty details and shipping issues. Anyway, they've already responded and are evidently as aware of this 10mm hack thing as I try to be. I'll assume they do their figurin' with a slide rule and abacus and go for facts over my wow's all I got factor. They're saying that a 3" STI would be workable, IF, you can find a stout enough recoil and hammer spring to slow everything down. We're not talking 20-22# Tanfoglio/Glock stuff here. They recommend #26 in the STI 5.0 guns, and stated that a #32 recoil spring would be needed for a 3" barrel to prevent cracking from jarring. Damn, boy, there's no way a #32 slide can be racked without proper forearm training. Either that, or I'm getting pretty weak in my old age (an excuse I use to successfully get out of various chores). ;D
(http://commonbullets.com/uploads/forearm-training.jpg)
The real trick is finding stiffer mainsprings. Is the Tac III a Officers frame or a government/commander grip frame length?
Pretty sure it's an Officer's frame size. It also appears as if their "Tactical" lineup no longer includes a 40 S&W. That info wasn't offered by STI when we were discussing it (emails). They probably assumed I had the 4" Tactical SS that I wanted to convert. That one is do-able, but it too requires a stout recoil spring, in the 28 lb range, according to them. At that barrel length, there are in-the-box ready 10mm's already out there (4.25"). The Tactical SS 3.0 is the size I would be more interested in, if I could even find one in 40 S&W. Then, like you say, that recoil spring issue.
Sounds like a custom Springs setup might fit the bill.
Yeah...And you can't really get stronger mainsprings for officers frames. I have looked.