I’ve got a Holland 577 2 3/4”NE that was sent back and opened to 3” 577/650. It was noted in the ledger that re-regulating was not required. With 25” barrels it places Woodleigh 650s running 1805fps sideXside. I always thought it was luck or trickery, but I found that original 2 3/4” 650gr Nitro and 3” 650gr Nitro loadings were the same. I used it on a Cape Buff 2yrs ago to test penetration, but no definitive results other than it will stop a charge and the Woodleighs hold together.