I went 100% non lead six seasons ago:
I've been using Yewtree 114gr TLRs in my 6.5x55 for four seasons now
@Selous kindly loads them for me with 49.0gr of N555 powder, MV 3080 fps. I have had virtually no issues on a couple of hundred + reds, fallow and roe.
I found factory copper was just not performing well on the hill hinds at ranges over 250 yds. There was minimal reaction to shot, blood trail and a narrow wound channel/exit.
With the Yewtree I've taken a few hinds at around 350 yds and the expansion has been impressive with exit wounds of golf ball size plus, they don't run more than 40 yds in general.
They do make a bit of a mess of roe if you hit the shoulder but I'm too lazy to switch zero with a separate low ground/roe round.
I put the increase in performance down to better bullet design and pushing it faster.
I've shot around 100 deer with my spare rifle, a 30:06 with Geco Evo and they have been effective on reds out to 350 yds. It's the only round I have tried with them as I start with the cheapest brand and my rifle (Sako 85) liked them! In fact they were cheaper than the lead Norma I used.