11 December 2014
Assuming you are sizing the bullets to .226 or smaller, the only thing that could be forcing the bullets to be seated that far back with that bullet is a bore too tight for the nose of your bullets. When you push a sized bullet into the bore fairly hard (20-30 pounds of force) with a dowel and drive it back out where are the marks that stop forward motion?
The 223 rifles I have tried bore riders in (a Ruger, a Remington, 4 Savages, and a Tikka) would all accept a .220 nose - a couple without making decent land marks on the nose.
It is hard to find groove diameter but easy to find bore diameter. I would suggest slugging just ahead of the throat. If the groove diameter is under it might, or might not indicate a tight tight bore diameter. With a skinny bladed caliper you might be able to measure bore diameter on the slug. Has anybody tried that?
I don't know how hard the bullets were that you tried, but the simplest fix might be very soft bullets. If you have some soft (under 10 BNH) alloy available try some bullets of that. It could be that you have a tight bore that would be just right for your mold in that bore riding design if you can seat a soft bullet so only a little more than the gas check is in the neck
The next simplest fix would be another barrel. You should not be having that kind of trouble just because it is a 22. Bullets from all of my motley collection of bore riding 22 molds have have shot well (under 1.5moa) in all the rifles listed above. There is no magic involved.
The bore ahead of the throat could be reamed by the right gunsmith with right reamer for the kind of fit you want on the nose. This could give you a custom fit without the swaging that many do. If your mike is on, a .219” bore should take your bullets made of anything from linotype to 30 to 1.