On my new FS I polished all moving parts and installed an Apex Flat Faced Trigger & Forward Set Sear Kit (100-054). The factory trigger was initially gritty and heavy--7.5#. While waiting for the Apex parts I polished everything and dry fired a couple of hundred times. The factory trigger smoothed out nicely and dropped to about 6.5#, but I replaced it anyway.

Ran 100 rounds of 115 FMJ through it for break-in. Then 20 rounds of my carry ammo, Barnes TAC-XPD 115 grn. to ensure function.



Then I used a good rest under the trigger guard and at the bottom of the grip, carefully aligned the factory sights at 7 yards, and worked the 4.25# Apex trigger without disturbing the sight picture 5 times, and got this:



That's the OEM 4.25" barrel with only a little polishing on the barrel/slide engagement surfaces, no fitting except perhaps by the S&W assembler. <.75". I haven't tried it at 25 yards because my eye sight is not good enough.

The gun is capable of greater accuracy than I OTB. I do believe the Apex trigger helped.

I found this graph from Apex helpful to understand that their trigger stroke is shorter as well as lighter, making more accurate shooting easier.