Try some different cases (different headstamp, ie:Winchester seem to have the largest capacity's) The Lake City (LC) are mil-surp and have the least capacity.... Thicker in most all dimensions, but are very good,strong cases......But won't hold as much powder, and will develope higher pressures with a given powder weight..... Use them with caution..... Drop charges 5% below those recommended for Commercial cases..
You too have found out what I found out about 10yrs ago when Varget first came out......... I couldn't get the recommended charges to fit the cases, hence I couldn't get anywhere near the velocities published.
Varget works very well with bullets 69gr or heavier. Charges are lower, hence take up less space.....
However, for all 55gr bullets or heavier, I prefer the VERY similar Reloader15, and of course BLC2. These are denser and allow full charges.
Two other powders that are excellent, but are quite bulky for the .223 are IMR3031 an H4895. The max charge of Varget and H4895 are what you can get in the case and still seat the bullet for bullets 55gr and lighter...............
