Hello gentlemen. I feel I'm in a bit of a pickle with the AR I own when it comes to cast boolits and the assortment of reloading components I've got. I've got a couple of questions but let me give you some facts about my situation first. The 16" barrel has a 1/7 twist. The gun has a selector at the end of the gas tube to let me switch from normal pressure delivered to the action vs slightly higher pressures (for cold weather or very dirty conditions). It's a Sig 5.56 rifle. I also have a theory the selector can be thought of as switching from .223 pressures to 5.56 pressures; but I've never seen any documentation hinting at that concept. Anyway, most of the brass I have is 5.56 brass but the primers I have are*REM PRIMER 6-1/2*SMALL*RIFLE. I was given advise that 6-1/2 primers are fine for .223 but not the best for 5.56. To make matters a bit more dicey I've heard that my powder, H335, is great for .223 but not the best for 5.56 either. So all that to say I feel like I've got the components for reloading .223 but almost all of my brass is 5.56. So here are my questions 1) can I load a typical .223 load of H335 into my 5.56 brass with 6-1/2 primers and be perfectly fine? And 2) Am I going to have a real tough time getting cast boolits to pan out for me with my 1/7 twist rate? I know small cast boolits can be a challenge to start with. So far I haven't tried reloading any of my .223/5.56 stuff I bought *because I'm on the learning curve and working with my pistol components currently.*
My goal is to be able to cast for my 5.56 because it is so fun to shoot and very accurate with the j-word stuff I've been shooting so far. While I'm at it I might as well throw one more question in here. I'm under the impression that the only difference between .223 and 5.56 brass is that 5.56 brass has a thicker case wall than ..223. And all the outside dimensions are identical between the two meaning the internal case volume is smaller for 5.56 resulting in higher pressures generated from