I have Timneys in a couple, and I've just replaced the spring on others with good results
On the newer LC6 trigger, that is all that is needed sometimes, but with the older m77 mkII rifles, I've never had one that was livable with just a spring replacement. Careful honing, polishing and lighter spring always yields a safe 2.5 pound pull on all of my rifles. Never needed a Timney in any of my MKII's. In my m1917's, hell yes. Timney makes great triggers, but the mkII doesn't need them.