Joebeemish,
"I have the RCBS rock chucker. Very nice single stage press. No complaints. I added the RCBS piggyback to try progressive loading."
After reading forums for years, I've seen a good number of posts that the piggyback isn't the best device RCBS ever came up with.
"What do you think of the Hornandy lock-nload, RCBS 2000 and Dillon 550 as far as producing ammo with consistent OAL?"
Every single one of them will give you the consistent AOL you're looking for, as long as you're not trying to get bench rest consistency. If you are, use bench rest reloading equipment.
I see you're reloading rifle and pistol cartridges. One thing worth mentioning is how the various presses powder measures handle rifle powders. The Dillon measures can handle the extruded powders, but often you have to modify the measure to get it to meter accurately. The RCBS and Hornady measures do a much better job of handling extruded powders. The RCBS has the safest primer handling, but you have to use the plastic strips. The Hornady has one major advantage over the others because of the Lock N Load bushings in that with these, you can switch a single die out (insert, twist and click) without changing the rest of the setup. For instance, this allows you to change a full length resizer out with a neck sizer so you can reload for your only bolt action after you're finished loading for your semiautomatics. The Dillons and the Hornady both have case feeder options. The RCBS is cast iron. The Dillon 650 and the Hornady LnL both have 5 stations vs. 4 and both are quite fast, especially with a casefeeder.
"Most people seem to like any of these presses, but does anybody have some measurement data on OAL?"
I've never had to keep any data, I just set the OAL and check it occasionally as I reload. I've got a Hornady LnL. If you do a good job of adjusting the shellplate advance (simple and easy to do) it gives you very consistent overall length. I've adjusted this twice. Once when it was new and once when I switched out the old style subplate for the new style subplate that takes a casefeeder.
"I think this would indicate the "rigidness" of the shell plate to die plate. Another consideration (if these all have rigid assemblies) is how easy it is to swap calibers."
The Hornady is the easiest of the presses to swap calibers on. That said, all over the progressives you mentioned are easy to swap calibers on, so it's "relative." Now the cost of the caliber exchange parts can affect choices quite a bit.
"This is challenging and time consuming on the RCBS single stage & piggyback."
Any of the progressives you mentioned will be simple compared to the RCBS piggyback setup you have.
ALL of the presses you've mentioned are top quality and will reload good ammo. You can't go wrong with any of them. To pick one, you really need to take a hard look at features and decide which one has the features you want.
