If you look in the reloading section, you'll see a post I put up (one which folks seemed to step around) that lists a formula for determining the worth of putting up with an Ackley chamber. Basically, it it this: Velocity increases at 1/4 the increase in powder charge for a given barrel bore diameter and barrel length. So, if you could add 10% more powder, you might get 2.5% increase in velocity. "Handloader" magazine (US) did an investigation of this long standing "rule" in 2006 and found it to be correct. If, say, you had a 140 grain bullet at 2800 fps and you could get an additional 10% powder into the Improved case, you will get about 70 fps added velocity. If that's worth it to you, then go for it. ~Muir