nijalninja: Is the ammo you were using commercial or handloads? You mention boat-tail bullets which are known to not necessarily work in rifles with eroded throats. You might try some other type with flat base bullets. I would suggest using a lead-sled type of rest or front and rear sandbags to try to ascertain exactly what it is doing while taking yourself out of the equation (as much as possible). I'm not sure what you're hoping to see with a bore of the condition you describe but be aware that service standards for precision may not be what you expect. For example, a later CanadianEME Manual indicates that the "T" sniper rifle needs to group 5 inside a 3" by 3" square at 100 yds with front rest. These aren't target rifles! I had a somewhat similar experience to yours with a badly worn early 1942 Savage. As purchased it simply wouldn't group (or call it 10") at 100 yds. I noticed the "draws" were only bearing firmly on one side so I took the plunge and patched it. After that, and with commercial flat-based bulleted ammo, it would just make that 3" by 3" requirement so I called it a success and moved on. Very rough and uniformly pitted bore- tears up patches badly. Yours already seems to be showing (realistically) some fair potential, given the bore, so keep trying but don't expect miracles. Good luck with it.
Ridolpho