Pressure signs

[JB Short]

I have been loading for several 270WSM rifles the past few years, but ran into something that baffles me a bit. I am loading for the first time 140 accubonds w/Retumbo powder, Win cases and 215M primers. I used 71grs as a max and backed off 8% or 65.2grs as a starting point. By the time I reached 67.8grs my primers were cratering slightly. I tried a load at 69 and the bolt became sticky. This rifle normally shoots at near max loads without an issue. Does this seem unusual to anyone? I don't have a chronograph so I have no idea about velocity. Is that max already? The bullets are not jammed into the rifling.

 

[sp6x6]

Sound like it is and you should use chrono to verify max. The new lots of Retumbo has run hooter for some shooters on this site in past year, compared to older Retumbo. They have had to down load a favorite 1-3 grns.

 

[JB Short]

Thanks sp6x6, I have been finding some info since I posted this problem and it sounds like I need to back up a bit.

 

[flashhole]

There is another thread in this forum discussing the same problem with Retumbo. I wonder if the burn rate is the same, new to old. The chemistry could be identical but if the burn rate is faster it could explain the pressure issue you are experiencing.