Relying on a spring, rather than screws, crimps and/or solder for a tight, low resistance, sound connection just seems wrong to me.
Think I must be a Grumpy Old Dinosaur :-(
How can I joint a 6mm?
40A flimsy spring push connector. Coarse stranded as well as solid conductors are fine in these.
https://www.tlc-direct.co.uk/Products/WA173.html