One of our employees brought a Ruger All Weather 7mm mag to work today. He's shipping it back to Ruger for a friend of his so it can be rebarreled. There is a noticable bulge (or doughnut) about 5 or 6 inches from the muzzle. If you look inside the barrel you can clearly see a ring (for lack of a better word) inside the bore and the rifling from the ring to the muzzle doesn't appear as sharp as the rifling from the chamber to the ring.

So, any thoughts on what could have caused this? The only thing that came to my mind was that maybe it was shot with too much oil in the bore. It was only shot 5 or 6 times before the guy noticed this. I'm interested in what some of you knowledgable folks think.

Someting was in the bore at that point. A patch maybe. Oil would not do this. It always pays to make sure the hole goes all the way through before you pull the trigger.

An obstruction of some kind was encountered by the bullet. It could have been congealed oil, or a patch, or a bullet fragment, or a pebble, which reinforces the need to check your bore at some point before firing, if possible.

George

Here's some additional info. The bulge around the barrel appears very uniform. It's not higher on one side than the other. Likewise, the ring around the inside of the bore is uniform all the way around, not more on one side.

It doesn't take much to bulge a rifle barrel. All the things mentioned before will do it or a little snow, spider web(the ones that make a web like a little lint ball), mud-dauber nest, fuzz from a rifle case, styro-foam from the box. Any of those may do it. No way to know after the fact. It's all academic naval contemplation now. The bullet cleared the obstruction but not before the damage was done.

A uniform bulge is typical. My theory is that the bullet slows momentarily causing pressure to spike behind the bullet. The gas pressure is what bulged the barrel.

How well does the rifle shoot?

I have seen rifles that shot as well (or even better) after the barrel was bulged, than when they were pristine.

AC

If the rounds he was firing were reloads, then it is possible that one of the rounds had like a half powder charge or something.
It takes real ignorance and carelessness to bulge a barrel.
A customer many years ago brought in a 7.5" Vaquero with six 'rings' in his barrel and wanted to know if there was anything I could do.
Disgusting.

-Spencer

I too have seen some guns shoot WAAAAAY to nice to have a ring in the barrel. When I used to compete in PPC had a good friend who had a nice s&w 25-2. Shot mostly action shooting, but also saw it shot on paper and man would it shoot. He told me he was shooting fast double action and his powder hopper had ran out of powder, he drove another round down the barrel before he figured out what happened. Also knew a guy who hunted with a 7x57 with a ring just behind the front sight. The deer he shot never knew it had a bulged barrel.

Good luck and good shooting,
Eterry

Well, oil is most likely. Possibly water, but nearly always liquid of some kind. I have known of two guns that were bulged by oil. It is typicaly from guys who "oil" the bore very liberaly for rust protection, then forget to wide most of it out before shooting it. Nearly always out near the muzzle. Have seen pistols like this too. Oil to protect then damage it! ugh. Mostly, I hear if it shoots good leave it and learn. Ruger may not fix it either!!