Ah the day of abbreviations,,, how sad! Sorry but Craig C is 100% correct, the term FTF has always been known in the firearms industry as a "failure to feed" and is related to semi auto and automatic firearms,, I too when I saw the thread subject immediately thought this was in the wrong forum and should be in the semi auto forum??
Fail to fire can be easily fixed. I have had seen this with some double actions, and one single action. Every instance was simple to remedy. First never ever use a reduced power hammer spring, this is not good even if the revolver does fire! This will reduce lock time at the least, creating a less than ideal accuracy platform, it can cause ignition issues even if the firearm does fire which also can cause accuracy issues. It can cause a dangerous misfire or worse yet hang fire which can allow the firearm to fire even after the hammer has dropped. A weak hammer spring has and can cause issues without the owner even knowing it.
I will also say to much spring power can cause less then perfect accuracy as well pounding the frame disrupting a steady platform as the round is ignited!
One thing I have found on a couple Ruger revolvers double action, is with the hammer itself. It did not have enough travel stopped by the hammer before the transfer bar was intruded on the firing pin far enough. This was a simple fix on revolvers that I have encounters, and one of them only displayed this in double action firing. I simply reduced the height of the step in the hammer that limits how far it can fall against the frame with a fine file and hone. Light strike in this manner I was able to eliminate, I also seen better groups in single action deliberate testing after doing this on one of these guns, the other I had not ever tested, but had caught the issue first time shooting it in double action.
I really never give this much thought, I take it as one of the little things that go along with owning the most robust hand guns ever made and the finest sporting revolvers ever made, to me it's trivial when I know I have chosen the finest hunting revolvers available anywhere near their price! Easy fix, nut unlike some I consider tight throats a good thing since I shoot only what I cast and load myself, this just assures I can have it custom throated to it's absolute optimum for my purpose! I also figure this is one thing easily taken care of with the trigger job. One more thing I plan on doing immediately after buying the revolver before I ever buy it, my personal opinion is any responsible firearm owner should easily be able to fix this problem without sending it back to Ruger, and my guess is many have created the problem themselves without knowing how to properly improve the action but attempt it anyways??? just a my guess?