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
Hunting
The Basics, Starting Out
Handloading dies question
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="Kennibear" data-source="post: 926990" data-attributes="member: 51650"><p>"Off the lands" means the bullet is seated back from contact with the origin of the rifling. Try to see it it this way: you drop the bullet into the chamber and it slides forward into the barrel until it rests against the start of the barrel's rifling. Then you take a case and push it onto that bullet and close the bolt behind it. When that bullet/case comes out of the chamber the bullet is seated far out enough to contact the lands if it is put back in. This is called "jammed" or as long as the bullet can be safely seated out of the case where the bullet is just touching the lands. Anything shorter than that is going to be "back off jammed" or the measurement less than that is the bullet "jump" to the rifling. Example:</p><p></p><p>In 375 Ruger, my current development project, maximum COAL is 3.340" which is the common maximum COAL for most SAAMI "standard length" cartridges e.i. 30/06, 300 WinMag, 7 mm RemMag, 270, etc.</p><p>The Speer 270 grain SpBT 375 caliber bullet is in full contact with the rifling at a measured length of 3.557"</p><p>The Savage 116 detachable box magazine has an actual inside length of 3.528" even though the standard length cartridge max is 3.340". Some clearance is required in the magazine to function reliably and keep the bullet noses from being battered when the gun recoils. So I have loaded the preliminary trial ammo at a length of 3.400". This is short enough for the magazine, longer than standard to reduce the bullet jump, and safer than having the bullet "jammed" against the rifling with a load that can only be single fed into the chamber rendering the rifle a single shot.</p><p></p><p>So the math is: 3.557" jammed length - 3.400" loaded length for a bullet jump of 0.157". Or, the bullet is seated "off the lands" 0.157". When fired the bullet will slide unhindered for 0.157" when it then stops against the rifling origin until pressure rises high enough to push the bullet into the rifling and out the barrel. This is more than most people like to have their bullets "jump" but less than if the bullets are loaded to SAAMI's maximum COAL. If the cartridges stay put in the magazine under recoil I will definitely load the bullets out further consistent with them feeding up out of the mag into the chamber.</p><p></p><p>All of this makes perfect sense the first time you measure the contact length of a bullet in your rifle and start dialing in the seating die for seating that bullet. My 45/70 has almost no "jump" at SAAMI maximum because the bullet leade is so short in Ruger's chambers. Might explain why it is so accurate.</p><p></p><p>Feel free to PM any questions you have as I will gladly help anyone starting out in this fabulous hobby.</p><p></p><p>KB</p></blockquote><p></p>
[QUOTE="Kennibear, post: 926990, member: 51650"] "Off the lands" means the bullet is seated back from contact with the origin of the rifling. Try to see it it this way: you drop the bullet into the chamber and it slides forward into the barrel until it rests against the start of the barrel's rifling. Then you take a case and push it onto that bullet and close the bolt behind it. When that bullet/case comes out of the chamber the bullet is seated far out enough to contact the lands if it is put back in. This is called "jammed" or as long as the bullet can be safely seated out of the case where the bullet is just touching the lands. Anything shorter than that is going to be "back off jammed" or the measurement less than that is the bullet "jump" to the rifling. Example: In 375 Ruger, my current development project, maximum COAL is 3.340" which is the common maximum COAL for most SAAMI "standard length" cartridges e.i. 30/06, 300 WinMag, 7 mm RemMag, 270, etc. The Speer 270 grain SpBT 375 caliber bullet is in full contact with the rifling at a measured length of 3.557" The Savage 116 detachable box magazine has an actual inside length of 3.528" even though the standard length cartridge max is 3.340". Some clearance is required in the magazine to function reliably and keep the bullet noses from being battered when the gun recoils. So I have loaded the preliminary trial ammo at a length of 3.400". This is short enough for the magazine, longer than standard to reduce the bullet jump, and safer than having the bullet "jammed" against the rifling with a load that can only be single fed into the chamber rendering the rifle a single shot. So the math is: 3.557" jammed length - 3.400" loaded length for a bullet jump of 0.157". Or, the bullet is seated "off the lands" 0.157". When fired the bullet will slide unhindered for 0.157" when it then stops against the rifling origin until pressure rises high enough to push the bullet into the rifling and out the barrel. This is more than most people like to have their bullets "jump" but less than if the bullets are loaded to SAAMI's maximum COAL. If the cartridges stay put in the magazine under recoil I will definitely load the bullets out further consistent with them feeding up out of the mag into the chamber. All of this makes perfect sense the first time you measure the contact length of a bullet in your rifle and start dialing in the seating die for seating that bullet. My 45/70 has almost no "jump" at SAAMI maximum because the bullet leade is so short in Ruger's chambers. Might explain why it is so accurate. Feel free to PM any questions you have as I will gladly help anyone starting out in this fabulous hobby. KB [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Hunting
The Basics, Starting Out
Handloading dies question
Top