Hey Fred, Welcome back. We missed you.
MT3030 seems to be the only one who got my idea. It was not to increase the powder capacity of the 223. It was only to get a longer neck on a 223 case. And a more accurate cartridge. I just think with a longer neck it could be a more accurate cartridge. In general, a 222 will out shoot a 223 any day of the week, all other things being equal. Part of this reason is the case neck length. The 222 has a neck that is 1.5 bullet diameters long. The 22PPC has a case neck length that is 1.28 bullet diameters long. The 222 mag has a case neck length that is 1.18 bullet diameters long. The 223 has a case neck length that is 0.9 bullet diameters long. By running a 222 mag case thru a 223 FL die it would bump the shoulder back by about 0.0289". Not much granted, but it would then give a case neck length of 0.2927 which is 1.3 bullet diameters long. The 223 is my favorite to shoot, I just wish it had a longer neck. By running a 222 mag reamer into a 223 chamber not only lengthens the neck but the overall case length too. Course you could always stop the mag reamer short of moving the shoulder forward but it would not give you the maximum neck length you could get by just making the standard 223 chamber with the longer neck. You could still shoot standard 223 cartridges if you wanted to. Kind of like shooting 22 longs in a 22 long rifle chamber. Course you wouldn't want to do this on a regular basis but you could just the same. Accuracy might suffer a bit too. I think it is generally understood that a longer case neck tends to make for a more accurate cartridge. I have made chamber casts of both my 223 Handi and my 223 Savage barrels. The lead or throat on the Handi is about twice as long as the one on the Savage. By making the neck longer it would eliminate some of this long throat and consequently long jump to the lands. Who knows, maybe you can make a silk purse out of a sows ear. I can't see where it would be very costly to just make the standard 223 throat longer. Anyway it is something to think and plan about when you can't get to the range or your waiting on parts to arrive for a favorite project. :?