I was range testing some loads in my 300 Win Mag, and some of my ammunition would not chamber. The brass was weight sorted, and some were from another rifle. I had FL sized them all, so the fail to chamber was a bit of a surprise.
Bottom line, the brass from the other rifle had been fired in a larger chamber than mine, with a near full pressure load. Some measuring of fired cases revealed that my chamber was near minimum in the region just ahead of the belt, and my FL die would size that area of the case about -0.001", on the cases fired in my rifle. The brass from the other rifle were touched by the die, sized a fair bit, but because the brass is fairly thick at that point, the brass sprung back enough to be too big to chamber in my rifle. In my 300 Win Mag FL die this area doesn't get reduced much, it ends up at app 0.514" and will not chamber. My 375 Weatherby die reduces this to app 0.513" and this allows the case to chamber, just. In the picture the shiny part just ahead of the belt is the area that "rubbed" as the case was chambered. This area now measures 0.5125".
The SAAMI minimum spec for the chamber in this area is 0.5136". My chamber is a whisker smaller than that at this point. Interestingly, the CIP spec for a minimum chamber has this @ 0.5142".
In my Waters book, Ken measured 0.515" on his brass, for a max load.
Just a FYI post, to show the interesting stuff that shows up. This rifle was built in 1974, is well used, and I'm assuming it shot mostly factory.
Bottom line, the brass from the other rifle had been fired in a larger chamber than mine, with a near full pressure load. Some measuring of fired cases revealed that my chamber was near minimum in the region just ahead of the belt, and my FL die would size that area of the case about -0.001", on the cases fired in my rifle. The brass from the other rifle were touched by the die, sized a fair bit, but because the brass is fairly thick at that point, the brass sprung back enough to be too big to chamber in my rifle. In my 300 Win Mag FL die this area doesn't get reduced much, it ends up at app 0.514" and will not chamber. My 375 Weatherby die reduces this to app 0.513" and this allows the case to chamber, just. In the picture the shiny part just ahead of the belt is the area that "rubbed" as the case was chambered. This area now measures 0.5125".
The SAAMI minimum spec for the chamber in this area is 0.5136". My chamber is a whisker smaller than that at this point. Interestingly, the CIP spec for a minimum chamber has this @ 0.5142".
In my Waters book, Ken measured 0.515" on his brass, for a max load.
Just a FYI post, to show the interesting stuff that shows up. This rifle was built in 1974, is well used, and I'm assuming it shot mostly factory.
