Hate to revive an old thread but I finally got around to putting an order in for the SBR a couple weeks ago. Got it in the mail last week, installed it, and cut two turns of the bolt latch spring as mentioned above. Went out to the range last Friday night and did about 30 mag changes only loading about 5 rounds per mag, with 3 different 25 round mags (my original one and 2 new ones). The bolt locked back after the last round every single time using Walmart Federal 550 Bulk.

Really happy with it as I have had my BAD Lever on my Colt 6720 for a while now and always wanted to put one on the 15-22 as well. Thanks to NDZ for making a great product!