...One way to get a lighter trigger pull on a Gen 4 is to put a Gen 3 trigger bar in the gun. The Gen 4 trigger bar has a bump on the piece that raises the firing pin safety up. The bump also rubs on the slide during the trigger pull causing a heavier trigger pull. The Gen 3 trigger bar does not have the bump.........I have a Gen 3 trigger bar in my Gen 4 model 19 and it works fine and lightened up the trigger pull.
I have heard the statement that the older trigger bar, without the "bump" (see photo) is better, and will reduce trigger pull. It's tempting to believe that the bump would introduce some friction which could possibly increase trigger pull weight, but I've always wondered if that assertion is true.
As it turns out, I happen to have a brand new Gen4 G34, and I have an extra old-style trigger bar (also brand new), so I decided to put the question to a test.
1) The G34 had the original ("Gen4") trigger bar, Part Number 3608, which I had polished.
2) I ran twenty trigger pulls and measured them, as done in the thread on the Connector Comparison Test.
3) I then removed the 3608 trigger bar, polished a brand new 357 ("Gen3") trigger bar, and installed it in the G34.
4) I ran twenty trigger pulls and measured them as I did in step 2.
Here are the results:
Original Gen4 Trigger Bar, P/N 3608:
Average trigger pull: 84.97 ounces, or 5 pounds 4.97 ounces.
Replacement Trigger Bar, P/N 357:
Average trigger pull: 89.1 ounces, or 5 pounds 9.1 ounces.
My conclusion is that the "Gen3" 357 trigger bar
will not reduce the trigger pull of the Gen4 G34. It will instead increase the trigger pull by about 4 ounces. Sorry to be contrary, but I really believe that testing and gathering some data is a valuable way to sort out the myths from the facts when we are talking about various means of improving Glock triggers.
Since I did not perform these tests on the same gun you have (a G19), and since the G19 uses a different trigger bar in the Gen3 version, it's possible that we would have different results with that gun. That said, I'm pretty certain about the results achieved on the Gen4 G34.
Here's the Data: