A tight inlet at the rear of the tang will result in damage IF the breech is no solidly bed, either with strong wood, or glass. If this was a VERY heavily recoiling rifle,
like the 4 bore Bill Raby is building, I would also consider inletting and bedding in glass, a piece of steel as a rearward "stop". I've done this on "unmentionable"
.375 and .45 calibre rifles, with complete success. Soft wood is prone to compression, which loosens contacts and creates movement.