My 38-55 shoots as well as a Browning 1885 45-70 I had in the late eighties shot. I replaced the scope todya, fired 10 rounds, excluding the 1st shot used for a sighter, it put 9 rounds into 1", exclude the flyer, 8 shots were in 5/8" (50 yards) my 44 Mag shot just as well, but as has been mentioned, the bullet must fit the bore. The 44 shot eratic groups till I started feeding it .432 bullets, then it began to shoot nearly as good as my 38-55.
My 30-30 had a groove diameter of .310 and a bore diameter of .307. The chamber however was spec on, if not a tad tight. The throat length was ideal for SAMMI spec ammo. I was never able to get what I consider decent groups at speeds above 1300 fps. The present owner shoots well with it.
My 357 Max drives me nuts. Currently I am shooting the RCBS 35-200-FN. At 1300-1400 fps it is shooting quite decently, but nothing to get overly excited about. The chamber itself is decent, but the throat is grossly oversize with a diameter of .379..... go figure :roll:
There seems to be a wide variation in NEF chamber and barrel dimensions, and there is no way to insure that what you get is up to a spec that is cast friendly. With present production barrels, a good cast shooter is at best a crap shoot, and generally, the defects that make it unfriendly to cast require a major change.
If you have a friendly gunshop/gunsmith that handles sizable flow of used guns; you may want to see if you can have some chamber casts made of different rifles in a chambering you want to work with. While I remain satisfied with my 38-55, and will likely continue work with the 357, (to heavily invested) I for one will not get another NEF with the intent of using it as a cast bullet rifle.