Believe it or not, SSD's are not the best choice for recording video, which is in effect what you are doing.
They don't do sequential writes any faster than an average platter drive.
They do excell at reads which is what gives the impression they are faster.
Grab this, it's from BlackMagic who is one of the most reputable names in video editing gear.
https://itunes.apple.com/us/app/blackmagic-disk-speed-test/id425264550?mt=12
It'll benchmark your drive and tell you what it can handle.