So on the check weight does it have to be a known weight , or could I just use a 168 grain bullet ?
Ideally, yes, it should be a known weight, which is verified by a more accurate and a more precise measuring tool, to an error smaller than your balance is supposed to be (+/- 0.1 gains, right). So your check weight should be its certified weight with a tolerance less that +/- 0.1 grains, such as +/- 0.01 grains, etc. I think bullets are routinely +/- 0.5 grains or more, at that weight.
So while you can check repeatability (precision) by grossly checking with an unknown weight (Is it 168.5 grains? Is it 167.5 grains? Etc.), it will only tell you if you have repeatibility problems, at that unknown weight (or comparative weight to the balance weight positions) and not if you are getting an accurate AND repeatable/precise weight measurement.
Also, if say you have some sort of crusty, cobwebs, or some other sort of friction at the fulcrum of your balance, effects on repeatibility may be different at low weights versus higher weights, as higher weights would more easily overcome any friction added to the balance.
So if you want to check repeatability with an unknown weight, do it around your charge weight to have the most value.
Now, all that said, let's go back to your problem description.
I zero out my RCBS 505 with the brass pan , throw a charge and trickle in a few more kernels to get my powder weight. Dump it in a case , pour it back into the pan and re weight it ( to double check myself ) . now I have to remove a few kernals ( lets say 4 ) of powder. Get it back to my weight and dump it in the case. Pour it back into the pan and now I need to trickle in 10-15 kernals ? The powder is IMR 7828 SSC. If I move the weights on the scale back to zero I have to re level my scale ( even though I haven't moved a thing ). What am I doing wrong ?
I don't think you are doing anything wrong other than over-correcting for perceived inadequacies of your equipment. (Yeah, go ahead and make jokes.)
As you trickle powder in the pan, you approach the balance point gently and gradually from the lower side of your target. When you recheck, you are dumping the powder in the pan, and the indicator/beam might oscillate above and below the target, until it settles. In the process, the approach to the balance point (where the pan and charge weight balance the beams and weights position about the fulcrum) might be different each time and certainly different that trickling to an end point, resulting in some minimal errors. Google hysteresis.
Add to that that there might be a few kernels remaining in the flash hole, you might have spilled a few, etc., and it begins to look like you have bigger problems, even though it may be your technique that is causing you to think you have problems.
I would expect to have to re-level the scale after putting the beam weights back to zero as even a minute change in scale position might show a 0.1 grain or more difference in indication.
In my experience, my Redding #2 might show +/- 0.1 grain from charge to charge. If I put the powder from the pan, into the case, back to the pan, back to the case, I would expect that I might lose powder along the way, bump the scale, a wind might break (don't look at me), some grains might stick to the pan, the funnel, the case, especially with fine powders, etc.
You are talking about 20 POWDER grains (of essentially what appears to be a relatively fine ball powder) on a charge of 59-63 grains. How many grains does it take to register a 0.1 grain scale movement? If it is more than 20, you are making work for yourself attempting to achieve powder measurement accuracy and precision beyond what the scale can produce.
Repeatabilty in technique in powder dispense and measurement is more important with imperfect loading equipment (which means consistent loads, whatever the charge) than to absolutely know you have 60.20000001 grains of powder in each in every load (which can't be done with common reloading equipment, anyway).
