I'm a bit of a 'reluctant advocate' of the chain / pullback system on the powder measure. I loaded 1000s of rounds on my early turret and Pro 1000, neither of which had a provision for manual return--the spring return was the only one available.
While the exact reason(s) remain a mystery, the spring return very rarely "hangs"--it does not return to recharge the disk. Long-time Lee users know that, I think. On the Turret, such a hang is typically readily spotted--the measure is right in front of you when it happens. On a Progressive, there's so many more things happening at once with three-to-five cases being worked on that you can miss that empty case and end up with a squib load--I know I did: They were extremely rare, but they would happen. I have a hunch that they happened about once every 5K-10K rounds--and I never blew up a gun, but I would rather it didn't ever happen again.
So, this year when I broke out Load-Master again, I did update one of the measures and installed the chain return kit, if only to "try it out." After setting it up successfully, I have come to appreciate it, simply because I worry less about that part of the reloading process. Because of its positive return action, that leaves monitoring the powder amount in the hopper to ensure reliable dispensing of the charge.
The chain-and-spring solution is ingenious, if cheap, but it does work and is really part of the Lee approach. The rod is a better idea, I think--and would probably lead to less maintenance stops for a broken chain. OTOH, if the chain breaks, it should be heeded as a warning to check out the dispensing system for a bind that caused it to break.
I've only loaded perhaps 2K of rounds with the chain return in place, but nothing has broken, stretched, or whatever. I do have to conscientiously remember to not leave the ram at full bottom in order to not stress the spring and chain, but I'm getting used to that now.
Jim H.
. Good luck Looks good.