joelkdouglas
Handloader
- Jun 5, 2011
- 1,310
- 3
I got my 7mm Mashburn Super back from Kevin Weaver. I think it's almost all sorted now. Kevin reamed out the chamber again with a deeper throat, and test loads today velocity is up, pressure down with previously used loads.
Why velocity is going up with the same powder I don't know...but I don't want to second guess. I assume it has something to do with pressure and bullet release.
Changes: I abandoned the Nosler brass. Kevin thought it was too soft and running into the bolt head. And as noted above the new chamber.
This brass wasn't previously fire formed. I'm trying to get some velocity data and fire form at the same time.
Here's the velocity numbers:
These velocities are really outstanding for the pressure. I was previously getting heavy bolt lift and deep ejector marks at 3050 fps with 160s. To get 3180 with 165s really surprised me with the first shot. Again, I don't know why velocity went up with the same charges, but they did.
No donuts, I form/trim/Fl sized the brass and then neck turned it before firing:
Downside, and I think the only thing left to sort out, is brass still gets into the ejector hole. I only saw this when the loads got a little more stiff (76+ gr Retumbo), but I'd be open to ideas how to get this to stop.
Why velocity is going up with the same powder I don't know...but I don't want to second guess. I assume it has something to do with pressure and bullet release.
Changes: I abandoned the Nosler brass. Kevin thought it was too soft and running into the bolt head. And as noted above the new chamber.
This brass wasn't previously fire formed. I'm trying to get some velocity data and fire form at the same time.
Here's the velocity numbers:
These velocities are really outstanding for the pressure. I was previously getting heavy bolt lift and deep ejector marks at 3050 fps with 160s. To get 3180 with 165s really surprised me with the first shot. Again, I don't know why velocity went up with the same charges, but they did.
No donuts, I form/trim/Fl sized the brass and then neck turned it before firing:
Downside, and I think the only thing left to sort out, is brass still gets into the ejector hole. I only saw this when the loads got a little more stiff (76+ gr Retumbo), but I'd be open to ideas how to get this to stop.
