Rick,
I have loaded many hundreds of Dacron filled cartridges and can not grasp the concept of Ringing a chamber unless the loader wasn't doing what he was supposed to:
But that said: Why bother when you can shoot tighter groups with powders that do not require fillers!
i'm all for faster powders with cast bullets. When one grasps that shooting cast in a rifle is not the same as shooting "jacketed' then "Grasp" the idea that cast requies different powders then Jacketed.... It is as simple as that!
Now if you wat to shoot cast at 3000 fps you got to figure out First: Why ! Then Second: How!
Being one of the odd ducks here, I agree with some of what you say and disagree with some. I think it would be much more accurate to say that "reduced loads require different powders than full-power loads, regardless of projectile". I routinely shoot cast bullets at near jacketed velocity with powders one would use with jacketed bullets, because that's what the job calls for. Also, I use the same powders for full-power loads in typical pistol cartridges whether using cast or jacketed bullets ("WOW, did he just say he shoots jacketed in pistols???" Yeah, once in a while, unfortunately).
Now for a little philosophy, not that anyone asked for it. I can answer why and how, sort of, because I don't consider a cast bullet to be relegated strictly to the arena of reduced target loads. Why shoot cast bullets at or near the full velocity potential of the cartridge? Same reason anyone would shoot jacketed bullets at or near the full velocity potential of the cartridge. How? VERY carefully! This is where the normal rifle powders and occasionally some compacting buffer come into play. Buffer can help simulate the engraving pressure of a copper-jacketed bullet with a cast-bullet load and bump the initial pressure for a good burn. Buffer also insulates the bullet base from the raw powder gas and makes a good pressure seal during the initial engraving event, and while it isn't called for in every or even most full-power loads, it definitely has its place.
Gas-operated rifles have certain pressure and gas volume requirements to operate, so the cast bullet loads must take this into consideration. An M1A or AR-15 isn't going to run off of Unique, but just because you want to shoot cast bullets in one doesn't mean you have to settle for making the rifle a straight-pull repeater. Believe it or not, buffer and even Dacron work fine in gas-operated rifles if used appropriately and can really help even-out velocity variations from some powders loaded to the lower end of or below their ideal pressure range. Sometimes a slow-for-cartridge powder shoots better than a "normal" powder for high-velocity cast bullet loads, but needs a little filler to make it burn correctly. A good example of this is the .308 with cast bullets in the 175-185 grain range, loaded up to 23-2600 fps. You wouldn't normally choose H4831 or Reloder 22 for that, even with jacketed, would you? But with cast, you might, and it's too slow for the cartridge unless packed in the case solidly. In this instance with 4831 or even H-414, taking up the slack air space with buffer helps quicken the burn, yet maintains the benefits of the slower powder's easy launch qualities and velocity potential.
