I thought a bit about resurrecting a thread as a zombie, but as a mod on another site I always cringe when that happens. I have been catching up on all the fun you guys have been having without me, and just read the discussion on AR-postal matches. I wanted to share a few of the thoughts I had as I read that thread.
I am big on AR's. My safe has eight completed AR's that I call mine + most of the parts for a ninth. The safe also stores an AR each for five of my six kids, my wife, my mother and my son-in-law. They always took mine at the range, so I made them all build their own. The sixth son is away right now but will complete his when he returns.
And, just in case, I have about 10 stripped lowers waiting on whatever idea hits me next. Problem with lowers is they are often on sale for $30 and it is just so easy to order 3-5. And my local FFL often charges a single flat fee for multiple transfers. So, I tend to stock up anytime I get below three on the shelf.
I specifically build one of my AR-10's in 358 Winchester as a cast bullet gun. 358 Win just begs for cast bullets in my world view. I built it light and handy too. I have had some challenges getting function with 310 grain Thumpers, but I think I have those issues worked out now. Next range session will tell the tale. I also have a 280 grain SP mold.
I also have molds for the 30's (308, 300 Blackout) and for the 223's. Like the 358 Win, the molds are for bullets that are on the heavy side for the caliber, running 200-230 grains for the 30's and 80 grain for the 223.
Lessons I have learned.
Plain base and gas systems don't get along. After years of running BobS' load in my Garands with gas checked bullets I decided I was going to save some money and try plain base. I got through 3-5 clips before I started having issues with the gun not going into battery. At first I feared I had horked up the op rod, but eventually figured out it was just excessive lead build up in the gas cylinder. Since then I am committed to gas checks, or a powder coat at a minimum in any gun with a gas system.
Ultra-light bolt carrier groups don't play nice with heavy for caliber bullets. My beloved 358 Winchester "scout rifle" was built to come in at 6.5 lbs unloaded with iron sights. Doing that in 308 is pretty achievable by using a pencil profile barrel and watching your weight elsewhere. But in 358 my barrel options were more limited, and I ended up with a more medium profile barrel. I ended up splurging on a v-seven titanium BCG to try to buy back some ounces. The gun just won't run with bullets over 250 grains. It fails to go completely into battery. It may be the 7.62 Nato brass I am using is not quite to spec, but I rather think it also could just be physics of the light BCG and heavy round. I have 1K Starline 358 brass now, and I have checked headspace with a regular full weight BCG. Next range outing will tell me if I finally have a gun that can run heavies, or if I need to order a 200 grain mold
So, having rambled a bit about how much I like AR's and how stupid I am sometimes in my build decisions, let me get to a point.
Right now AR's are cheap. And they are easy to build. And surplus ammo to feed them is cheap.
We mostly came to bullet casting via the ammo is costly, gonna save money, hey reloading and casting is really fun too route. This new group is coming here via a different path. Hey, AR's are cool, and wow, they are easy to build and cheap to shoot, but what other gun stuff can I DIY.
And I think that is going to be how AR guys get into casting bullets. Like me, at some point, they are just gonna realize that no matter how fun AR's are to build, you reach a point where you just can't store any more. When that happens, they are going to look for other fun to do, I did it myself, gun tasks, and cast bullets is an obvious answer.
Looking forward to developing better and more applicable information about AR's as well as learning from you. Here's to aluminum rifles and tiny bullets!