If you have a .204, no reason to build a 20P unless its just due to the .223 brass being easy as heck to get.
There is only a max of maybe 300 fps between them.
I had a 20P I built and was running 3800 fps w/32g bullets.
The 20 Practical will stay with the 204 Ruger all day. The Max between them is nothing. My 24" 20 Prac. will run a shade over 4000 FPS with a 32 grain bullet.
There are several reasons to build a 20 Practical. One is brass availability, you can find 223 brass everywhere. Another one is reliability. The 204 does not feed from all 5.56 magazines. The big one for me is the over all length. The 204 is to long for an AR. It is a common practice to lengthen out your OAL to get your bullet closer to the riflings. With a 204 there just isn't any room left. Bullets have to be seated deep in the case. [/quote
The 204 will feed perfectly with the Wright mag and that is a LANCER mag I have one and use them works great!!!!]
Exactly my point. The 204 WON'T work with just any magazine. It takes some trial and error to get one that will work. I'm not trying to bash your 204. I'm just pointing out the problems with the 204 in an AR.