I am building a heavy barreled ar and which chamber do I want?
I want to be able to touch the lands with a 50 gr Vmax bullet.
My choices are a 5.56 chamber,Sammi 223 chamber or the wylde chamber.
Whats the difference between these three?
Thanks for your help.

Go 5.56, then you can shoot anything without worry.
The leade of the chamber is shorter in a .223 chamber, good if you are shooting .223 for accuracy, not good if you want to shoot 5.56 milsurp ammo, as it will be too tight. With a 5.56 chamber, with the slightly longer leade, you can shoot any ammo safely, both 5.56 and .223.

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If you are thinking Wylde Chamber, I'm assuming you are looking at a Rock River Arms piece?  I called Rock River a week ago and asked this very question.  The sales guy indicated that the Wylde chamber in their varmint is rated for 5.56mm ammo.  The primary difference is that the chamber was modified to ease extraction.  The "downside" to it was that you will have to resize your brass if you reload.  Which you should do anyway.  

Perhaps you could give them a call and see if you get the same story?  You may also wanna see what they say about twist rate too.  (I'm suspect of sales people)  I'm in the middle of my first build, and will probably buy a RRA 20" flattop upper...  When I have the cash that is...