To me your loads and velocities say you are on or close to the SAAMI 62k pressure limit.
I ran my numbers through GRT and am around 61400 at 39gr h4350 peterson brass. I've got a longer than saami freebore so should be a touch lower in reality. I've got a 20' barrel averaging 3055 fps but just cracked 100 rounds through barrel. GRT underestimates my measured velocity by about 40 fps if that's helpful at all. Seeing zero pressure signs primers look new when popped other than the firing pin impact.
You must not being using grt correctly. Freebore is irrelevant and it would be with 1 or 2fps if you correct the burn rates and use measured case volumes like you should.
Still a decent program...... and damn close im running 42.2 grains of n555 behind a 80.5 berger 3205 fps from a 22" ...same rifle dose 80 eldx at 3175 with 41.5 n555 and 41 grains with a 80 eldm dose 3129 fps all load using alpha brass and fed 210 m. All loads half moa or under 3.633" with 80.5 and 3.685" coal with 80 eldm/x zero pressure all loads are at least a full .5-.6 under anything that would even signify pressure at all.
Your definitely not high those load are closer to 59k-61 depending on freebire length and seating depth ect your gtg
If your showing zero signs of pressure you could go up most likly .3-.7 more most likly max befor seeing slight ejected marks or swipe or flat primers ext. I typically run min .015" off and most everything at .025-.032" off and can most the time stomp a little harder.
How long of a barrel? Im running n555 with a 22" and getting 3200 but this barrel only at 90 rounds needs more break in.
That is a big delta between measured and predicted velocities, my differences have been 50fps or less so there may be a variable off. I just went through this exact thing wanting to run 4350 and 88s without a lot of data and also not wanting to push my brass to hard on first fire. That's what led me to start checking my work with GRT. I settled on 39gr for now going 3060 from a 20" if that helps at all. Grt shows 61400 for that load. Tried single shots up to 41gr and still no heavy bolt or ejector marks but when I popped the primers they were starting to muffin top or flatten very slightly. I had a pretty flat spot in velocities between 38.5 and 39.5gr then a pretty big jump from 39.5 to 40 so took that as a pressure sign and will stay at 39 at least until all my brass is formed. At 39gr the primers are coming out looking like new. As stated by others I just cracked 100 rounds on barrel so things could change
22'', I think the summer heats has sped it up some also. I won't push it any harder, if anything, back off a little. I'm actually using 39.5 in a Wilson Steel barrel from Urban Rifleman on another forum, that's a little over 3200fps right now, I'm breaking it. It shoots so well, with zero pressure at that node, I'm sticking with it for now.
