I had major leading issues with my 620 the one time I shot some Blazer 158 gn LRN in it. Took about 10-12 hours to get the barrel clean and I won't repeat that mistake.

Now, what I have read is the you can shoot cast bullets in the ECM barrels BUT lubrication is CRITICAL. Use the wrong lube or an unlubricated bullet and the leading will be beyond belief. Since I don't reload at this point I cannot recomend any particular lube, all I can recomend is shooting jacketed bullets.

As for the accuracy produced with the ECM barrels, I can't complain at all. Personally, I believe that my 620 is capable of shooting to 1/2 inch at 50 yards, with it's tensioned barrel it's a 4 inch rifle when I'm shooting well. I also have an ECM barrel in my 6 1/2 inch 610 and normally group it between 2 1/2 and 3 inches at 35 yards from a rest using a reflex sight. One of these days I'll mount my scope on the 610 just to see what it can do, personally I suspect it'll probably shoot between 1 1/2 and 2 inches at 50 yards. IMO the ECM barrels are at a minimum just as accurate as the older broached barrels and it's possible they may be more accurate. One positive for the ECM process is that it seems to be much more consistent from barrel to barrel than the older method of rifling.