Need suggestions on increasing neck tension

[searcher]

I would do as Stool says. I have shot competitively with an AR-15 (not AR-10) and never crimp ammo. You just need to get enough tension on the neck as others have described. Do put just a bit more than you find you need to cover variables such as differences in neck thickness, whether the cases have been cleaned of all powder and carbon (which otherwise act as a lubricant in the neck), etc. A little more is better than not enough as a rule...