Counter Bore

[T Bran]

I see this term a lot in surplus rifle discussions would someone please explain the process and it's effects on the weapon.
Thanks
Troy

 

[rcmodel]

Old military rifles often have the rifling worn away at the muzzle from years of cleaning rod use.

Counter-boring is simply running a reamer or drill bit down the muzzle far enough to remove the worn rifling and get down to where the good rifling ends.

Thinking of it another way, you are moving the crown of the rifling from outside the muzzle to further inside the muzzle.

rc

 

[Act2325]

Well put RC. I have gotten decent accuracy from some old mil-surps that were counter bored. Most 91/30's are counter bored and some shoot great!

 

[morcey2]

A counterbore is a quick and dirty, yet extremely effective way of salvaging a barrel with a damaged crown or rifling in the last inch or two of the muzzle. The Finns made it a habit to counterbore every captured or purchased mosin on which they didn't put their own barrel.

Matt

 

[Act2325]

Very true Matt. The Finns were smart. They knew the average Russian soldiers weren't "gun people". I can only imagine what they ran into with captured rifles. Its funny. You can find lots of Finnish produced Mosins without a counter bore. Those obviously had replaced barrels. Then there were the captures that were almost counterbored 99.99% of the time. Simple solution to a big problem when you need guns for men and not much industry!

 

[T Bran]

Thank you gents makes perfect sence to me now and now I know what to look for in a surplus rifle.
Troy

 

[Maverick223]

A counterbore if generally thought ill of, but it often aids accuracy for tired, old bbls, and also helps to protect the muzzle. In many ways it is a desirable addition, but it usually reduces the value a bit.