problem with 300 win mag chambering

[woodbutcher]

I chambered a barrel in 300 win mag. I went out to test fire it and had difficulty chambering round. I took the barrel back off and took a piece of brass with bullet seated to correct depth and marked the bullet ogive and neck with a black magic marker. When I inserted the round in the chamber I stopped at the point it bound up and turned it several times. When I removed the round the bullet had a distinct mark on the ogive. Upon inspection with a bore scope I found a copper ring at the neck/throat juncture. What would best way to remove this burr?

 

[Gundoktr]

Set the barrel back up and re-cut the chamber. This time use a good cutting fluid. If that is not the problem, get the reamer re-sharpened.

 

[woodbutcher]

Used Relion and Moly Dee for cutting fluid and it works very well. This is the exact formula Gordy Gritters uses.

This is the first chamber the reamer has cut. There is a slight burr around circumference at the end of neck and

beginning of throat. It should be easy to remove I just need to know the most prudent way to do it without

removing material where it does not need to be removed.

 

[Larryh128]

Look closely at the reamer, think there's an issue. The pilot could also be undersize for the bore. How deep does the ring appear to be?

 

[woodbutcher]

I taper bore the chamber and use a loose fitting pilot. A lot of people that use this method use no pilot. This chamber is very concentric so I know it works. I will have to examine the reamer under magnification to see if there is any anomaly.

 

[Rustystud]

Could the brass put into the chamber was just a little long? When a seated bullet was inserted and the bolt closed the pressure between the bullet and throat pinched off a ring of case neck leaving a deposit of copper.
The reamer may have a short neck, check the reamer and the drawing or spec compared to SAAMI spec.
Make a cast of the chamber and measure.
All your questions have an answer.
Nat Lambeth

 

[eww1350]

I taper bore the chamber and use a loose fitting pilot. A lot of people that use this method use no pilot. This chamber is very concentric so I know it works. I will have to examine the reamer under magnification to see if there is any anomaly.

I wonder if the taper boring went in too deep and left the ring there. set the barrel back one thread and run the reamer in to correct headspace and see if that clears up the problem..


Eddie in Texas