I'm glad to hear Kevin mention Benchmark. I've got some rounds loaded with 2 different bullets with Benchmark. I'll probably even try those before I load up any more with Varget. Then I'll take the best of both and compare against each other later.
I know that FL sizing is the overall preferred method with semi auto's. Hard to disagree with the reasons why. However, I wanted to see if I could get good functioning with NS only for one or two fireings.........Successful test so far, 40 rounds fired, not a single malfunction.
I won't push my luck very far with this particular gun, and I'll probably go to FL sizeing after all the cases have 2 fireings on them.
Yes, FL sizing is an absolute must with any Service Rifle, not just the ARs. You may or may not need S/B dies, that depends on how tight the chamber is, how "loose" the sizing die is, etc.. Most don't, but it sure doesn't hurt anything, and it's better to err on the side of more clearance.
Not saying that N/S cases won't work in the ARs, just that at some point you will have problems with them. It's a bit like making a mad dash across a freeway during rush hour traffic, surviving, and declaring that it's perfectly safe; it's not, and eventually, you're gonna become a bumper sticker on a Mack truck if you keep doing it often enough.
If you're lucky, you'll eventually get a round that won't fully chamber, but is jammed so tightly in the chamber that you can't extract it by simply pulling on the charging handle. This leads to setting the butt on the ground and stomping on the charging handle (yes, I've seen military armorers doing this, frantically, on the line at Perry). Not to mention the really ugly possibllities that this potentially invites, you can usually count on a bent charging handle, and some other cosmetic damage to the reciever. All in all, not a good thing.
It's foolish to learn from your own mistakes, if you can learn from the mistakes of others. Trust me, it's cheaper, less painful, less embarrassing and saves a whole lot of frustration this way. Full length on the Service Rifles always, neck sizing (if you absolutely must) only on the bolt guns.
I have a standard M4 with a 16 barrel. A few summers ago, I spent three months formulating the perfect combo and ended up with CCI 400 primers, 55gr. Moly Vmax bullets, Winchester cases and 24.5grs of Varget. My best five shot group at a 100yrds was 3/8”i.e. one raggedy hole. Because of part swapping, I ended up re-sighting in the rifle and somehow ended up shooting paper plates at 595yrds. I shot a few rounds of miscellaneous stuff out of my range bag and couldn’t hit the 2x4’ backstop. I then found ten rounds of my Varget loads. The first five shot grouped at 3.5” and the second at 4.5 “. That deer season I decided to take my newly found tack driver hunting and dropped a large three point at 316yrds.
I have also used Varget in another AR I built, a lightweight 18” SS fluted barrel with 1:8 twist. No paper results with this one but to my surprise I was able to detonate two water jugs, one right after the other, at 758yrds. One jug was taken with a Black hills 69gr HP and the other with a Berger 70gr bullet loaded with the same load described above.
Yes, it is true I have a bias for Varget it just seems to work.