willowwolfe1975
Member
- Joined
- Jan 31, 2016
- Messages
- 16
Hi everyone,
I hope someone can help with my pressure issue.
First off the rifle is:
7MM STW
28" Lijja barrel.
Trigger tech trigger.
NDT ESS chassis
Scorpion optic.
I built this gun around the Berger 195 EOL.
Using data provided by Berger.
Info received for IMR 7977, 7828, and Retumbo.
I have no issues with 7977 or 7828 and have developed insanely accurate loads. However, with these powders I have pressure signs in the mid range of load data.
My loads were developed over the winter (-35-40C) where midrange still produced pressure.
My load for retumbo was also midrange for the data provided (76.3g), I am not up against the lands (40 thousands away), and this load worked best.
Now it is much warmer, about -20. I was shooting and blew out primers (scary). So I backed off and even made some test rounds at 0.5 grains below the minimum load suggested by Berger (74.5). Today, (-14C) I started with the less than minimum load (74.0) and again blew primers; actually had to hammer the bolt open. The pressure slammed back the ejector pin and snapped off the keeper pin so that it is now lodged within the bolt (thats okay I single feed anyways). I was under the impression that retumbo was not too temperature sensitive. I have also backed off the lands another 10 thousandths of an inch (now shorter than bergers COAL).
Any ideas??
My only other thought is with resizing my brass. I only neck size, and I am on the 4th reload. Could this have anything to do with it?
Please help!
I hope someone can help with my pressure issue.
First off the rifle is:
7MM STW
28" Lijja barrel.
Trigger tech trigger.
NDT ESS chassis
Scorpion optic.
I built this gun around the Berger 195 EOL.
Using data provided by Berger.
Info received for IMR 7977, 7828, and Retumbo.
I have no issues with 7977 or 7828 and have developed insanely accurate loads. However, with these powders I have pressure signs in the mid range of load data.
My loads were developed over the winter (-35-40C) where midrange still produced pressure.
My load for retumbo was also midrange for the data provided (76.3g), I am not up against the lands (40 thousands away), and this load worked best.
Now it is much warmer, about -20. I was shooting and blew out primers (scary). So I backed off and even made some test rounds at 0.5 grains below the minimum load suggested by Berger (74.5). Today, (-14C) I started with the less than minimum load (74.0) and again blew primers; actually had to hammer the bolt open. The pressure slammed back the ejector pin and snapped off the keeper pin so that it is now lodged within the bolt (thats okay I single feed anyways). I was under the impression that retumbo was not too temperature sensitive. I have also backed off the lands another 10 thousandths of an inch (now shorter than bergers COAL).
Any ideas??
My only other thought is with resizing my brass. I only neck size, and I am on the 4th reload. Could this have anything to do with it?
Please help!
