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Rifles, Reloading, Optics, Equipment
Reloading
seating depth
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<blockquote data-quote="royinidaho" data-source="post: 102656" data-attributes="member: 2011"><p>"How much can seating depth affect preasure?" This is where I wish I had a strain gage pressure measurement device to go with the chrono. Maybe it would prove my 'obversations as incorrect'? But my observations have been when the bullet is seated further out, pressure and velocity go down noticably. I then increase powder to usually achieve a higher velocity at the same pressures as w/the shorter seating.</p><p></p><p>I tend to load at close to maximum pressures and velocities and I think its a bit of a different world up there. The rate if increase of pressure line it trending pretty steeply as a small amount of powder increase will result in a very large increase in pressure if the powder is all getting ignited w/in the bbl. So 'careful' is the key word.</p><p></p><p>W/my 27" Lilja in 270Win the first indication of pressure is a titch of a sticky case upon extraction. The cam action of the bolt has to move the case very little then it just falls out. This makes for a very distinctive indicator of too much pressure. Using this indicator I increase the COL then increase powder till I get to that "sticky point" then increase COL, repeating the process until I get max out on the velocity or achieve the velocity I desire. With the 270 the goal was 3200 FPS w/130gr bullet. When I got there I stopped figuring that was sufficient for the cartridge. Could have gone more but 3200 was enough. This process achieves maximum velocities and most accurate loads and cases that last more than 20 reloads.</p><p></p><p>My experience is the same with a 338 Win. Less pressure with longer COL. I have had it rebarrelled to 338 RUM and would expect to find the same trends.</p><p></p><p>This seems to conflict with the above post (Rifle Mag article) which apparently was a bit more scientific/lab approach???</p><p></p><p>HTH.</p></blockquote><p></p>
[QUOTE="royinidaho, post: 102656, member: 2011"] "How much can seating depth affect preasure?" This is where I wish I had a strain gage pressure measurement device to go with the chrono. Maybe it would prove my 'obversations as incorrect'? But my observations have been when the bullet is seated further out, pressure and velocity go down noticably. I then increase powder to usually achieve a higher velocity at the same pressures as w/the shorter seating. I tend to load at close to maximum pressures and velocities and I think its a bit of a different world up there. The rate if increase of pressure line it trending pretty steeply as a small amount of powder increase will result in a very large increase in pressure if the powder is all getting ignited w/in the bbl. So 'careful' is the key word. W/my 27" Lilja in 270Win the first indication of pressure is a titch of a sticky case upon extraction. The cam action of the bolt has to move the case very little then it just falls out. This makes for a very distinctive indicator of too much pressure. Using this indicator I increase the COL then increase powder till I get to that "sticky point" then increase COL, repeating the process until I get max out on the velocity or achieve the velocity I desire. With the 270 the goal was 3200 FPS w/130gr bullet. When I got there I stopped figuring that was sufficient for the cartridge. Could have gone more but 3200 was enough. This process achieves maximum velocities and most accurate loads and cases that last more than 20 reloads. My experience is the same with a 338 Win. Less pressure with longer COL. I have had it rebarrelled to 338 RUM and would expect to find the same trends. This seems to conflict with the above post (Rifle Mag article) which apparently was a bit more scientific/lab approach??? HTH. [/QUOTE]
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