So you are saying you get stretching at the web and you have the primer backing out? That's interesting. Are you sure it isn't just the shoulder blowing forward rather than the web stretching back?
What is the copper bullet you are using and what COL are you loading to? Also, what is the water overflow capacity of one of your fired (but not yet resized) cases? (To find case water "overflow" capacity, you leave the spent primer in the fired case and weigh it and measure the case length and then fill with water level with the mouth and with no meniscus and weigh it again. The difference in the two weights is the case water overflow capacity in grains).
In QuickLOAD with a Barnes Flat nose seated out to 2.782", I couldn't get past about 2200 fps without raising pressure (adjusting case capacity) to 62,000 psi. GRT's powder model is a bit different and it let me reach 2380 at about 54,000 psi.
What is the copper bullet you are using and what COL are you loading to? Also, what is the water overflow capacity of one of your fired (but not yet resized) cases? (To find case water "overflow" capacity, you leave the spent primer in the fired case and weigh it and measure the case length and then fill with water level with the mouth and with no meniscus and weigh it again. The difference in the two weights is the case water overflow capacity in grains).
In QuickLOAD with a Barnes Flat nose seated out to 2.782", I couldn't get past about 2200 fps without raising pressure (adjusting case capacity) to 62,000 psi. GRT's powder model is a bit different and it let me reach 2380 at about 54,000 psi.