300 win mag problems

[sniperjwt]

A Friend of mine just got his 300 Winchester Magnum back from gunsmith I am working up some loads. But I have noticed that when using new brass it chambers just fine but I bought some once fired brass and I cannot get them to chamber even after full length sizing them. I did the magic marker trick and marked the case to see where it is rubbing and it is just above the belt. I measured new brass and it measures around .505 and this once fired brass measures .512. The loads that I have shot out of the gun with the new brass I have been able to re use those pieces of brass. I sent the dies back to RCBS to see if there was anything they could do and the guy said that the dies I had we're fine and that there was nothing they could do. So my question is there anything I can do to be able to use the 150 pieces of once fired brass that I have or am I stuck trying to find new brass for the gun?
Any help would be appreciated
Thanks

 

[Lefty7mmstw]

Small base dies and tell your gunsmith to clean up the chamber. It likely has a bit of a burr at the tail of the body just before the belt. I've seen this on a couple of factory chambers and corrected it with fine grit wet or dry and oil. Your smith should correct it for you though.
Btw my browning 300 win blows once fired brass out to .513 just ahead of the belt and redding fl dies work just fine with it.

 

[sniperjwt]

What does it size them too?

 

[Greyfox]

It's very possible that the rifle that your once fired brass was shot in had an oversized chamber and and it will be difficult to get the brass sized down with a standard spec dye. Even though you run the brass through a standard dye the brass can have memory and spring back after sizing just enough to create difficult chambering. I have experienced this a few times over the years.

 

[rick523]

It's very possible that the rifle that your once fired brass was shot in had an oversized chamber and and it will be difficult to get the brass sized down with a standard spec dye. Even though you run the brass through a standard dye the brass can have memory and spring back after sizing just enough to create difficult chambering. I have experienced this a few times over the years.

+1 I have also ran into the same problem with 7mm Rem Mag's.

 

[sniperjwt]

It's very possible that the rifle that your once fired brass was shot in had an oversized chamber and and it will be difficult to get the brass sized down with a standard spec dye. Even though you run the brass through a standard dye the brass can have memory and spring back after sizing just enough to create difficult chambering. I have experienced this a few times over the years.

I did think the same thing after I bought the first 50 once fired and they did not work. I figured it would not happen twice so I found somebody that had 100 once fired brass and bought them and I have the same problem with them.

 

[Lefty7mmstw]

What does it size them too?

.507" at the same point just above the belt/ web where it first swells