Product Overview
If you have a CryoStructure or Blackwidow lower you will need to modify the Spring on our BFM nutsacks. You can either modify spring on the actual Magazine or purchase the Spring Kit. The CryoStructure/Blackwidow Lower spring indent is not wide enough to fit our spring. The Spring is the part that helps retain-the magazine. You will need to do the modification using a Dremel or Small Grinder to the portion of the spring engaging the lower to 7/16 width. (see pictures on this page that show the modification. Once you have taken 1/16 off each side We encourage you to apply "Blue" to the spring. We use black oxide to treat the spring to prevent any sort of corrosion. Bluing or black oxide will help spring remain in excellent condition. Kit Comes with 1 spring and 2 ,1/8 inch black rivets. You can perform this operation while on the magazine-using caution not to touch the Nylon Top, -or you can remove spring and re-rivet when complete. Feel free to call our email our team to discuss further details.