I don't think I've ever seen PSI data for 5.56 as that's not a SAAMI recognized round; have you seen any data on what is max pressure for 5.56?
MM
Yes, Western Powder's load data lists separate data for 223 and 5.56, with pressure data for both. Since they are the makers of that powder, it's the best source I know of.
I don't consider 5.56 pressure too hot for an AR, that's what they are designed to handle. That seems like an odd statement and I'm not really sure where you're coming from there.
Seems like a lot of guys here are used to going by 223 data, and think anything approaching 5.56 specs is "really hot". Never mind the millions of ARs actually shooting factory 5.56 ammo...
Also, I know from experience the typical "rule of thumb" estimates for velocity loss are essentially worthless; actual velocity loss when you cut down a barrel is so variable depending on the load that a guess of 25, 35, or 50 fps per inch is rarely correct. For example, light bullets usually lose more velocity in short barrels than heavy bullets, and those typical rules of thumb are based on medium to light bullets in hunting rifle barrel lengths. None of that is similar to what we're discussing here with 16" barrels and heavy for caliber bullets.
