It all depends on the strength of the seeds. Sounds like you're using store bought seeds that have been washed, because 300g of unwashed seeds would be quite strong. Some unwashed seeds can have 1mg of morphine per 1 gram of seeds.
The first time I tried poppy seed "tea" (i.e., poppy seed wash) I did alot of research and sourced the strongest seeds (the kind used by poppy seed tea addicts), and washed an entire pound (454g) and drank it. I didn't have an active tolerance at the time but was under the impression that the effect would be pretty weak so I figured a whole pound would be a good dose. I was shocked to find that within 45 minutes I was high as hell, and it kept getting stronger. The first 2-3 hours were great, but then it continued getting stronger and I started getting concerned. Then I started throwing up and nodding pretty uncontrollably, combined with a sort of dysphoria presumably from the other alkaloid. I took a bunch of stimulants to try to combat the nodding and spent the next 6-7 hours pinned to a chair, nodding and occasionally getting up to throw up. After something like 10 hours I started feeling more manageably high and the euphoria started coming back. My eyes were totally pinpointed for a good 30 hours.
Yet if one drinks a pound of store bought seeds that won't happen. Part of my underestimation of poppy seeds came from my prior attempts years ago to use large amounts of store bought poppy seeds (which had zero effect).
Becareful though, seeds are no joke. That poppy seed tea I made with the pound of unwashed seeds felt like it could easily have been a lethal dose for someone without a tolerance (granted I didn't have a tolerance at that time but I have a high permatolerance). For instance, there is no way my girlfriend could have survived a dose like that without medical intervention; she would have lost consciousness within the first few hours and choked on her vomited. So again, don't underestimate poppy seeds like I did.