I have read where guys have said you can load a little hotter for a bolt gun, is this true ?
Meh. Not as much as it might seem.This is where an adjustable gas block on the AR would come in handy
SAAMI pressure for 223 Rem is 55,000 PSI . Its been said, the difference in measuring methods are the reason for the 7,350 PSI difference??5.56 X 45MM NATO
CIP COMMERCIAL AND NATO/MIL SPECIFICATION (62,350 PSI)
This is your answer... I would hope your AR has a 5.56 chamber , which should be stamped on the barrel... If not stay way away from 5.56 territory... Sit down and read this and understand the difference in the two Chambers and why the 5.56 can be loaded hotter... Also pay attention to what barrel length the data was recorded on , I have seen them as long as 24 inches for 5.56 and most ARs are between 16 and 20... Reading pressure signs on an AR is different than a bolt gun also.. Then you get into over gassed guns especially on the M4 which is very common , ejection patterns and what to look for and how to tune buffers and springs if it is...etc etc etc....http://www.accuratepowder.com/load-data/ gives hotter Nato load data. NATO data should be used only in 5.56 chambers. Imo. SAAMI pressure for 223 Rem is 55,000 PSI . Its been said, the difference in measuring methods are the reason for the 7,350 PSI difference??
https://www.accurateshooter.com/cartridge-guides/223rem/ this is a great read on the difference in chambers and a lot more.