If you buy a separate press for depriming and precision loading, for a fixed press the Lee Classic Cast is less expensive than the Rock Chucker and does what it will do. The Lee finish is a bit less perfect. RCBS guarantees for life while Lee is just for two years. RCBS customer service is stellar, while Lee's is just very good. On the other hand, I understand the RCBS castings are now made in China where Lee is made here, if that affects your decision. I don't know what portion of the RCBS line is made in China vs. what portion is made here. I know their balance beam scales are made here by Ohaus. I also have a Forster Co-ax press, that I do all my precision rifle loading on, and it is a better design than either of the other two, IMHO, but it costs more rather than less than the RC.
I have a Dillon swager and it works fine. Other than the horizontal handle stroke vs. the Dillon's vertical, and the lower RCBS price, I don't see much difference between them. The Dillon has the advantage that there are videos at YouTube showing how to automate a portion of its function (the raising and lowering of the case anvil and, in one instance, actual ejection of the finished case to a pile).
On cleaning, you can buy a massive cleaner like the large Dillon vibratory cleaner if you want a lot of capacity. You do have to watch what happens with the dust when you separate cases from it. There is a lot more lead in that dust than around a casting bench, and it's in water-soluble salts (the unhealthy form). The mechanical reasons for cleaning are to protect your sizing dies from grit scratches, to shine the cases so they are easier to find in the grass after a self-loader flings them away, and to get out carbon so it doesn't promote barrel erosion. Only the stainless pin and ultra-sonic methods thus far seem to succeed in all three areas completely. So for your precision work you may want to use one of those methods. If you don't mind losing some cases in the grass, you can just shake them in a milk jug with soapy water, rinse and dry to remove dirt. You can add a little citric acid to get a degree of yellowing and removal of heat oxidation. You can also add just enough to bring the detergent pH to 7, so it doesn't affect the brass at all. The vibratory tumbler will do the same, cleaning off grit, but will als0 polish the outside and, to a lesser degree, the inside. You can also put cases into a rotary tumbler with the same solution, but without pins, which gives you more capacity for cases, but the insides and primer pockets won't get very clean as they do with the pins in place.
If the case lube die adversely affected primer pockets it wouldn't be usable and they wouldn't make it. You will still want to lube case necks on the inside for bullet seating, and that has to be done before you start the load cycle.
I'm not sure what you mean by using .277 die sets for 6.8. They only make the X-die in two .277's and those are .270 WSM and .270 Winchester. Neither will work with the 6.8 SPC. Case sizing requires an exact match to case profile all over. Unlike straight wall pistol cases, where a .38 Special and .357 can share dies, once you have sides that taper and shoulder you are in for unique sizing dies for each cartridge.
Likewise the Redding Competition Seating dies are cartridge-specific and must be made not only for the correct bullet diameter but with the whole case profile matching the die so the sliding sleeve matches the case body. So you 6.8 Rem will require a different loading routine.
Fortunately, Forster's Benchrest Seater die is available in 6.8 SPC. It also has a micrometer head option. The only difference between this die and the Redding is the Redding has a floating seater stem rather than a fixed one. However, the Forster die's reputation is good. I don't own any only because I started with the Redding as my first sliding sleeve seater, and it worked so well I developed brand loyalty. But I don't honestly know how much difference that one feature really makes.
If you are using the X-dies you only have to use a trimmer once on each case, but for a large volume even that can take awhile since you have to trim more than usual. I have not been too impressed with how the various case chucks work on most lathe trimmers in general, so I use a Wilson trimmer for small runs instead. I use a Giraud for high volume. A Gracey costs less and also works well. Like the special RCBS cutter, these tools have cutters that deburr and chamfer and trim simultaneously, but we're talking only two or three seconds per case. You can find YouTube demos of the various trimmers to get an idea of what I'm talking about.
You may want to be careful using the term 'pigg-back' in a post discussion RCBS equipment. RCBS has a progressive adapter for the Rock Chucker Supreme called a Piggy Back, so some confusion is possible.
A number of cartridges share common head designs that can share shell plates, but your rifle rounds all have different head dimensions and will need different shell plates.
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