You don't say what calibre. 6.5 55 maybe? have you tried other powder weights, is 44gr the start load with rl19 if so it may well be that the pressure is low and the case is not expanding to fit the chamber allowing propellant gas back between the case and the chamber wall. I have experienced soot on the case necks before but not as far down the case as you describe. Perhaps someone with more experience will be able to shed some more light on the problem.
I don't want to teach anyone to suck eggs but IF it were me I'd make up 4 or 5 at 44.5 gr the same at 45gr and so on up to near max load,all the same OAL, wait for a calm day and try them in order, checking for high pressure signs as you go. Use a different target for each group and it should become clear what weight powder gives the tightest group. I do my testing at a minimum of 200yds as it is easier to see the differences between groups. Hope this helps. Let us know how you get on.
Sounds like 46gr is the load then. Have you still got the soot problem? Are you full length or neck sizing? if just the necks you may get better groups from the fired cases.If looking for best accuracy I try to keep my cases at the same number of firings EG you have 2 cases together 1 having been fired once and another fired 5 times the neck tension will be different due to the brass around the neck being harder from working on the 5 times fired case. (I hope that makes sense)
the fired cases im neck sizing , the new full.as for soot im still getting a little bit .
i must say it was a good feeling see that sort of group was being to think this was not for me.
just made up another 10.
Sooty necks are normal, soot past the shoulder (obturation) is not. Are the primers flattened out, was recoil excessive compared to factory rounds? Make sure you chamber clean rounds, anything with lube/oil on will batter you and the rifle.
just tryed some of the loads, once fired not to bad a little bit of soot but not very good group.the new brass soot all over the place it look't like round marks and a very thin ring around the brass ,stop soon as i found this.
primers look ok, there did seem to more recoil ,tried a factory round ,no ring around the brass.
Your problem could be a number of things, but those cases are filthy, the ring could be caused when you extract the case, as you lift the bolt the case turns in the chamber, you could have crap in the chamber or a shard of metal.
I've just put together a dummy round using a 120g nosler bt. At 3.128 inch oal there is only 0.25 inch of bullet in the case.The bullet has a boat tail so there ain't much left to seal the neck.
Also the Lee Collet Die info sheet reccommends an oal of around3.000 inch.
Give a shorter round a whirl...I don't think accuracy will suffer.