Thread: suppressor pressure

Ok for those who know more than me and there's quite a few of you , can you explain this? I have been developing loads for my rifle using it's muzzle brake. Started at 62gns working up in .5's to 65. had no pressure signs and good speed so stopped as I was happy enough. I settled on 64gns for no other reason than up till then every .5 gave 30fps and after that it was 20 then 10 so figured a good place to settle.
Put a new suppressor on , hardy gen 6 and first shots stamped the brass and very tight bolt. Reduced loads to 62gns and same thing. While still at 62gns I remove the suppressor and didn't put the break on as I didn't have it with me and all things back to how they should be! Not a hint of pressure or stamping or sticky bolt. The hole is the right size in the suppressor and can't see anything wrong with it.. It's done up tight and only just resting on the barrel. I checked the specs and it's the right size for a 7saum . What's the go? Where has all this extra pressure come from?