I used new bullets at 448 they were and 480 grain. They had nasa lube 4 grooves, a postell bullet it was, from the bull shop. I bought a 100, only place had a full 448 for me. Thought sure this is what I needed. 73 gr of 1fg, fired fairly far apart and cleaned with Thompson center cleaning patches every shot. I had a clean barrel. So why would it overheat so bad in the morning that I needed a damp cloth and time too cool her.