Forums
New posts
Search forums
What's new
Articles
Latest reviews
Author list
Classifieds
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Rifles, Reloading, Optics, Equipment
Reloading
Pressure changes with seating depth
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="johnnyk" data-source="post: 1751786" data-attributes="member: 307"><p>Push the bullet back far enough into the case and it will raise pressure because of the now smaller case capacity that has been created. I'm speaking with reference to going by the reloading manual and starting with a SAAMI seating depth, which I personally never do. I usually start at .010" off the LaG's with every bullet I try, no matter the ogive.</p><p>Although I will say I recently received a valuable lesson with seating depth(s) while trying to find a sweet spot for the Berger 95gn VLD in my 6BR Norma. I tried various depths and then called Berger, which they suggested I try it jammed but at charges closer to starting loads, as some of their techs had discovered this. I reduced powder levels to starting loads and tried the jam. That worked great and I found a superb load within a few shots. That's just that bullet though and not all Bergers or rifles will react this way.</p><p>As you slowly work back from/off the LaG's pressure will decrease until you reach a certain spot or depth. Then you're approaching "SAAMI" depth's and in some rifles that may be magazine depth or with some bullets it may be lightly compressed. </p><p></p><p>I read an article a while back about seating depth for revolver cartridges, wherein the author was using SAAMI depth reloads (read as pressure) and then seated the bullet out farther, up to his cylinder's length. His findings were once the bullet was seated out deeper, pressure went down enough so that more powder could be added to increase velocity and still be within the pressure limits established by SAAMI.</p><p>This made me think of Weatherby cartridges, which are loaded to their established SAAMI length/pressures. The chambers, however, have a bit of freebore, which causes the bullet to pick up speed before it encounters the LaG's of the barrel. This concept seems to work well.</p><p>I recently rebarreled my .300WinMag. The 26", factory barrel with SAAMI cut chamber shot really good and was what I call a "fast" barrel. The primers always seemed to be cratered though, no matter the load, from mid to top loads tried. I never worried about it because no other pressure signs were apparent.</p><p>I assume this was because of a tight chamber. Finding the seating depth for reloads with various bullets was a little depressing for me. I think a cartridge just looks better with a bullet run out farther than the "book".</p><p>I replaced that shot out barrel with a 8t, 28" Pac-Nor, which I also ran a Ryan Mantha finishing reamer through before installing. I think this reamer was created so that the 215gn Bergers could be loaded with a COAL in the 3.7" range, as it did for me. Accuracy and speed are still there but no cratered primers and no other high pressure signs. It's the same charge as the old barrel liked but feels milder in the P-N</p><p>barrel. The benefits of this chamber are not only apparent with Bergers but also with the 212gn ELD-X's. Their ogive is not the same as the Berger (more tangent that secant, kind of a hybrid look) but the velocity and accuracy are almost identical but the ES & SD are a little lower for the Hornady's. Go figure.</p><p>In summary; you have to find that ideal seating depth for pressure and accuracy. Too much in either direction (into the lands or into the case) will cause excessive pressure, relative to your powder charge.</p><p>This is long but I hope it helps.</p></blockquote><p></p>
[QUOTE="johnnyk, post: 1751786, member: 307"] Push the bullet back far enough into the case and it will raise pressure because of the now smaller case capacity that has been created. I'm speaking with reference to going by the reloading manual and starting with a SAAMI seating depth, which I personally never do. I usually start at .010" off the LaG's with every bullet I try, no matter the ogive. Although I will say I recently received a valuable lesson with seating depth(s) while trying to find a sweet spot for the Berger 95gn VLD in my 6BR Norma. I tried various depths and then called Berger, which they suggested I try it jammed but at charges closer to starting loads, as some of their techs had discovered this. I reduced powder levels to starting loads and tried the jam. That worked great and I found a superb load within a few shots. That's just that bullet though and not all Bergers or rifles will react this way. As you slowly work back from/off the LaG's pressure will decrease until you reach a certain spot or depth. Then you're approaching "SAAMI" depth's and in some rifles that may be magazine depth or with some bullets it may be lightly compressed. I read an article a while back about seating depth for revolver cartridges, wherein the author was using SAAMI depth reloads (read as pressure) and then seated the bullet out farther, up to his cylinder's length. His findings were once the bullet was seated out deeper, pressure went down enough so that more powder could be added to increase velocity and still be within the pressure limits established by SAAMI. This made me think of Weatherby cartridges, which are loaded to their established SAAMI length/pressures. The chambers, however, have a bit of freebore, which causes the bullet to pick up speed before it encounters the LaG's of the barrel. This concept seems to work well. I recently rebarreled my .300WinMag. The 26", factory barrel with SAAMI cut chamber shot really good and was what I call a "fast" barrel. The primers always seemed to be cratered though, no matter the load, from mid to top loads tried. I never worried about it because no other pressure signs were apparent. I assume this was because of a tight chamber. Finding the seating depth for reloads with various bullets was a little depressing for me. I think a cartridge just looks better with a bullet run out farther than the "book". I replaced that shot out barrel with a 8t, 28" Pac-Nor, which I also ran a Ryan Mantha finishing reamer through before installing. I think this reamer was created so that the 215gn Bergers could be loaded with a COAL in the 3.7" range, as it did for me. Accuracy and speed are still there but no cratered primers and no other high pressure signs. It's the same charge as the old barrel liked but feels milder in the P-N barrel. The benefits of this chamber are not only apparent with Bergers but also with the 212gn ELD-X's. Their ogive is not the same as the Berger (more tangent that secant, kind of a hybrid look) but the velocity and accuracy are almost identical but the ES & SD are a little lower for the Hornady's. Go figure. In summary; you have to find that ideal seating depth for pressure and accuracy. Too much in either direction (into the lands or into the case) will cause excessive pressure, relative to your powder charge. This is long but I hope it helps. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Reloading
Pressure changes with seating depth
Top