39gr of H4350 in my 18" was 2980fps. I started seeing faint/light E marks at 40gr, and a heavy bolt lift at 41gr. I dropped back to 39gr and called it for H4350. I went to 40.5gr with N555 at 2940fps and no PSI signs,Here's my actual fps and then what GRT calculates with a Sebert factor of 0.5. This is with a 16.5" barrel (PVA 100FB) and a Scythe Ti suppressor.
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