Drilled and Tapped Pre ‘97 Mossberg 590 Mariner question.

[Gridiron504]

Hey guys. New to the forum. I just got a Mossberg 590 Mariner that was made before 1997, which is important because that’s apparently the year they started factory drilling holes for rails and sights on the receiver. I own a two other 500’s and decided that this one I was going to have some fun with. So I sent it off to an experienced gunsmith to get four holes drilled and tapped on my 590 in order to mount a rail and a small red dot. The vortex venom. I bought a rail from brownells designed for the 590 and got the holes drilled in the exact spot they would be in from the factory so that I can interchange rails if I ever need to. But my question is, when I got him and mounted my optic, I noticed that one hole was drilled and tapped all the way through the receiver. You can see the hole when the bolt and slide are pulled back. I will include pictures below. I know my way around a weapon, but I’m no gunsmith. Does anyone know if this hole will have any effect on my firearm in the future or after a large amount of range use? It doesn’t interfere with the bolt whatsoever.

 

[Bobster]

I always liked the shiny Mariners!

Holes for mounting scope rails usually go all the way through in many firearm receivers I've seen. It is not uncommon. If you removed the bolt you would probably see the other holes. About all i would do is make sure there is no roughness inside the receiver and don't use screws that are too long and protrude into the receiver...