Re: .204 Vrs .223
Ditto what Kevin said.
I have found a huge variation in data on the 223. One barrell does such and such, while another does something else.
The difference between the two is great.
In my humble opinion the bigger distractor for the 204; is barrel life.
My dad has a M70 pre-64 in 220 Swift, he bought it new in Bozeman. He has been very careful to never push it past 3700 fps in order to preserve the barrel. We will be taking it to Wyoming this summer on a Grandfather, Son, Grandson PD shoot. It will be a very special shoot/road trip. The rifle still shoots 1/2 moa.
Point being, push anything at 4000 fps on a steady basis and you will looking for a new barrel.
So if you down load a 204 to preserve the barrell, how does it then compare to a 223 Rem? Fine for PD's and etc.
Snohomish Co. Washington
NRA Life Member