cramps from kick sets

I have the problem of cramping up from kick sets -in the hamstrings specifically. I try my best to warm up and ease in to kick sets but can't get past 150 meters of moderate kickboarding before cramping up. Would love to get some input on how to warm up properly or technique pointers to alleviate cramping.
Comments
Don't kick?
Seriously though, I don't do kick sets. I only ever do 2-beat kick during OW swims anyway. No effort on my part on my kick will do diddly for my competitions.
We're all just carbon, water, starlight, oxygen and dreams
I had issues with my calves and toes cramping up pretty badly when I first started swimming marathon distances. Usually at around the 3-mile mark. My doctor recommended taking Magnesium. I did, and I absolutely stopped cramping. We're all different, but it's a possible remedy. All the best.
I tend to do a kick set after my warm up. My warm up is typically around 1600m and consists mostly of FS with some drill work. I wear fins for kicking and streamline position, so no kick board etc. Typical kick sets I do include 8 x 75m getting progressively quicker on each 25m with 15SR. 6 x 100m kick on lengths 1&3 fast FS on 2&4 with 20SR etc.