How so?
7mm-08 A.I. gained 120 fps with a 162 gr.
I meant just the 223 version. Each case will vary and parent case design will affect how much gain the Ackley form yields.
The more sloped the body of the case the more velocity will be picked up. IIRC for a 20 percent case volume increase exprct about 4 percent velocity increase, if you holding pressures the same.
10% is what I added to the load, once formed, and it made 10% more speed.
24.6 gr made 2800 fps (fire forming) 113 fps/ per grain of powder.
26.4 gr makes 3085 fps. 116 fps/ per grain of powder.
The pressure increases once formed. I have not been able to get the pressure up, while fire forming, even on compressed powder charges. The brass is just flowing so far, dropping pressure.
Now, can a .223 chamber make more velocity than a fire forming .223 A.I. chamber? I think, yes it certainly will.
edit: 7mm-08 A.I. chamber fire forming 2700 fps.
Fire formed> 3.5% increase in charge =4% more velocity.