Springs are a rat's nest. If you're buying a S&W revolver in 2018, then in the simplest possible terms...Originally Posted by Wildcat
There are 3 mainsprings to make note of:
Regular "flat" OEM.
Wolff Type 1 "factory equivalent"
Wolff Type 2 "competition only"
There are 2 strain screws:
New factory round butt (short) available at either midway or brownells
New factory square butt (long) No part number listed on either Brownells or Midway and looks like I don't have a spare bagged that still had a pn. Be advised, there's more than one of these if you go rooting through new old stock. Factory should be just using one, I think, and we're just talking about new production guns.
There are more combinations available once you go back a few years or go custom, but that's what you're likely to find on a new production gun.
This is where people get into trouble. They start to mix and match without really knowing how the differences are relevant.
If you combine a Wolff Type-I "factory equivalent" with the long square butt strain screw, then you're probably good. The downside is that this is actually not much (if any) better than the regular OEM configuration of flat spring + short screw. Oh well. At least you got to do some gun plumbing on your day off. The upside is that this is likely to be reliable, which one would hope. Since the weight isn't better than factory. Add another $100 when you list it on gunbroker because it's custom.
If you combine a Wolff Type-2 "competition only" with the long square butt strain screw, then you've found the combination the factory uses for their "pro/PC" guns. The downside is that it should work with factory magnum primers, thus being "reliable". I say "reliable" in quotes because IME it won't light off handloaded CCI 550s consistently. So it's probably borderline. The upside is that it's noticeably lighter than the regular non-pro/PC guns.
If you combine a Wolff spring of either type with the short round butt strain screw, you're liable to get knuckling. Maybe (hopefully) bad enough to let the spring interfere with the rebound bad enough that the gun won't fire. So at least you have a heads up what you did was really, really stupid. But if not, congratulations. You've got an awesome trigger that will probably not even light off crush fit Federals. Hopefully you're not carrying that gun in pubic with the notion of using it for anything important. Also, live fire after changes in the future so you can at least verify it works.
If you combine an OEM spring with the long square butt screw. Well. You'll probably notice. The trigger weight is now somewhere in the neighborhood of forty pounds and if you made the mistake of trying the action with the sideplate removed the hammer stud probably didn't go far. So it won't be too difficult to find all the parts when you box it up and send it back to the factory telling them "I don't know what happened. It just broke." The upside...well...there isn't one. Don't do this.
If you combine the OEM spring with the short square butt screw, you either tried one of the above and it didn't work, you didn't like it, or you work for S&W. In which case, great. Your lunch break is over. AOBC stock is down again, so we'll need you to pump up those numbers. Try not to use the wrong strain screws when you're churning out 90 guns per hour. Even the people don't actually shoot their guns notice when you do that, and we have to pay UPS so our social media presence isn't complete shit.
The above applies to the guns I've tried in IDPA/USPSA manufactured from 1999-2012 in matches from roughly 2000-2016 to the tune of 14k rounds of various primers, springs, firing pins and custom work. Firing pins are another rat's nest. Just buy Apex if you have to do aftermarket.
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