If you feel it's not overstimulation or colic, then it could be that he's going through a period of development. I read somewhere that when babies are learning a new skill, it's like they have a voice in their head that cannot be turned off which repeats the steps to the skill. Thus, they are more irritable.
Your baby has developed a sleep association. The sudden loud cry is due to overtiredness. At 4 months their sleep patterns mature. I actually wrote an article on this. Feel free to check it out. http://sgsupernanny.com/4-month-sleep-regression-what-is-it-what-can-you-do-about-it/
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Milk portion sounds normal. Could it be over stimulation before bedtime? young babies need time to wind down before bed. Do you have a sleep routine which you stick to?
Could it be colic ? does it happen at the same time of the day?
It could be overstimulation from the days activities.