I am just getting into finding a load for a new rifle. We went out the other day and ran a test with incremental powder weights through a chronograph. I have a custom rifle with a 24' proof barrel. I am using Berger 140 Hybrids which in my rifle would give me an OAL to land contact = 2.895. My test rounds were seated to an OAL of 2.865. I know some of these charges may shoot great, but we have not had the weather to go and shoot groups. I have not noticed any signs of pressure and have reached a low SD, but do I go any higher with charge weight? I was hoping to be at least at 2700. Another thought was that it was 48 degrees during the test. Do I need to about these loads when it is 90 degrees? I am fairly new to this kind of precision, so any insight or direction would be greatly appreciated.