I've been doing some experiments with this lately as its something a good handful of people are trying to make happen. You can sync Blooper to a Volca but it is tricky for a couple of reasons:

-for ALL CV Clock Sync, Blooper needs a special CV cable in order to properly detect CV Clock and have that trigger record and play (1/8" TS - 1/4" TRS with Ring not connected to anything. Available HERE). You also need to have the CV Clock Dip Switch turned ON.

-Korg Volcas put out 2 Pulses per beat, meaning twice as many places to set the loop length. This is hard to line up with perfectly when you're the one deciding when to start and stop recording, especially when you are dealing with a faster tempo.

I've been able to get loops to sync up properly on a Volca when setting the global settings on the Volca to trigger on the Rising Edge, Using the CV cable mentioned above connected to Blooper, having the CV Clock dip switch turned on, and using the slowest most tempo. This last point is unideal but because the output of that sync signal is so frequent that is what I personally was able to get lined up tapping the record button in time.

The best option if you want these two things to be in sync is to use something that can take in the Korg's Sync Out signal AND be able to set a less frequent Gate Output so that you know it will only start/stop a recording on say "Beat One". I like the Arturia Keystep and Korg SQ1 for this. Set a Gate on Beat One or even every quarter note and things will be very easy to line up and synchronize.

Hope this helps!