Really??
The pinhole isn't the problem....
The reason there is a pin hole IS. Metalurgic flaw, previous muzzle obstruction, foreign object embedded in a shotshell, magnetic pull of jupiter on the steel.....whatever caused led to the hole is a problem. Besides the very likely problems with the integrity of the barrel something catching on an irregular surface on the way out and then splinters of barrel/lead/wad etc escaping...or a collision resulting in a partial or full muzzle obstruction.....
Are any of these possibilities worth risking for the price of an 870 barrel...any barrel???
Launching lead shot down a steel tube driven by an explosive propellant charge several inches from your head/face/eyes.......
Not bashin' ya...truly mystified that the question is posed tho.