Gray Mark
macv,
I am assuming that this is a 'blued' GM barrel, and that the "gray mark" is on the breech face....? ?
If so, it is a combination of the bolt / breech contact and powder fouling...! ! Not to worry...! !
When firing my S&W K-22 revolver, the forward face of the blued cylinder gets a ring around each chamber; this is a combination of powder fouling and leading...! !
Remember, the 10/22 is a "blow back" action: the recoil and hot gasses of firing a round push the bolt rearwards, and as soon as the mouth of the case clears the chamber, the powder gasses blow out into the action; the returning bolt slams these gasses, and the debris they carry, against the breech face of the barrel, grinding the debris into the pores of the steel...! !
It is not a problem...! !
macv,
I am assuming that this is a 'blued' GM barrel, and that the "gray mark" is on the breech face....? ?
If so, it is a combination of the bolt / breech contact and powder fouling...! ! Not to worry...! !
When firing my S&W K-22 revolver, the forward face of the blued cylinder gets a ring around each chamber; this is a combination of powder fouling and leading...! !
Remember, the 10/22 is a "blow back" action: the recoil and hot gasses of firing a round push the bolt rearwards, and as soon as the mouth of the case clears the chamber, the powder gasses blow out into the action; the returning bolt slams these gasses, and the debris they carry, against the breech face of the barrel, grinding the debris into the pores of the steel...! !
It is not a problem...! !
