AR-15 Cast Bullets

I recently built this AR-15 from parts I had laying around, plus some new parts. The lower receiver is a Cavalry Arms Cav-15 that I put the parts kit in several years ago and used with a 16" A2 Dissipator upper from Model 1. Later I put the Dissy upper on a standard lower with collapsible stock, and traded it for a '77 shortbed F150 4x4 with a 460 and granny low 4 speed. That was a pretty good trade, I think. I wanted something lighter for a general knock-about AR anyway, so I bought a lightweight 16" chrome-lined barrel and installed it on an A1 upper receiver that I bought at a gun show a few years ago. I put a teardrop forward assist on it, and used an A2 aperture because I prefer the ghost-ring short range aperture over the smaller aperture of the A1 sight. The gas system is carbine length because it is cheaper, proven functional, and more likely to cycle with reduced loads (like these cast bullets, for example) as compared to the currently-popular mid-length gas system, or "middy" in the popular vernacular. I bought the standard black carbine handguards because they were on sale and they work. They are not tier one like a Magpul MOE, nor even tier two M4. They don't even match the color of the buttstock. But hey, I'm not an elite high-speed low drag operator; just a guy who likes to tinker for minimal expenditure. These small-diameter handguards worked in the '80s and they didn't suddenly stop working. Speaking of working, this load did not cycle the action. I was actually kinda' surprised, because the same load cycled my old Dissipator just fine. The Dissipator had carbine-length gas too, but this rifle has a heavier bolt/carrier/buffer assembly. The port may be smaller too, and this rifle is not yet fully broken in. No biggie. This load uses a 55 grain Lyman #225415 cast bullet over WC820, a fast-ish powder intended for .30 M1 Carbine. I will switch to something a bit slower to increase port pressure at the same velocity. That should do the trick. It did at least shoot to the same point of aim at 50 yards as the full-power ammo.