That recoil looks pretty severe.
Did the capsquares survive intact?
Yup. Everything appears to be fine. It's a pretty rugged little carriage. But that is a pretty big slug (around 14 ounces, I believe, or about a 6000 grain projectile). That's pretty big for such a little gun.
If I ever decide to get creative, I might think about taking Bruce's carriage design and blowing it up a bit, maybe putting 24" or even 36" wheels on such a carriage. Sure, the gun will look pretty tiny on a such a big carriage, but I think it might be a bit more suited to power it is putting out. Mabye I'll see if I can chrono the projectile coming out, if I can get my hands on a cheap/used chrono that I don't mind taking a beating (once I get a better feel for where it's hitting and can reliably repeat hits in a small enough target). Though the keyholing may make that impossible.