Restvitamin

Hi guys follow mws user from New Zealand just getting into doing a DMR build but I'm unsure about what strength of spring I should put in with my uac lightweight bolt, I had an issue where the nozzle got destroyed and just dont want it to happen again, I only have a 500 fps limit on my local fields and we dont measure joules so no worries on that part I've read all 70 pages and I'm pretty much gonna go with the tan bucking and hopefully a brass nub if it's possible to be delivered here. Thanks in advance for any advice.