I wanted to give a public thank you to both Bartz and Not Just Guns of Mason MI. I'm in the process of building my first 450BM AR-15. I purchased a 16" Bushmaster upper that came with 1 5rd magazine. I wanted to try out the Bartz mags after reading many of the threads here that spoke their praise. I contacted Bartz and was referred to Not Just Guns. Their service was prompt and they answered all my emails in a timely matter. Long story short, I have two 5 round Bartz magazines heading my way to eastern Ohio! Gotta get this gun built, have a public land SC hog hunt coming up first week of March.