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
Neck Tension
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="Mikecr" data-source="post: 1724912" data-attributes="member: 1521"><p>The scales of this internal ballistic process are extreme.</p><p>Very small, very fast, very sensitive.</p><p></p><p>Beginning with powder;</p><p>If you load a shell case with primer/powder and no bullet, on firing you get WOMF.</p><p>Fold a piece of paper and gently set it on top of the powder column,, on firing you get BOOM. With any real initial confinement you get POW.</p><p>Confinement leads to pressure, and pressure speeds the powder burn. All powders are variable in burn rate, and potentially to either end of burn rate charts.</p><p></p><p>On releasing of a bullet;</p><p>With partial neck sizing no further than seated bullet bearing, and a bullet in place, the neck OD is cal + neck thickness. Necks are not 'squeezing' bullets, but resting against bullet diameter with only their spring back force. How far would a neck in this common scenario have to expand to freely release a bullet? REALITY: Difficult to measure with an electron microscope. Perhaps billionths of an inch.</p><p>When folks claim you need ~2-3thou of neck clearance to be safe,, that's as likely analogous to 2-3ft on scale..</p><p>How much pressure would the primer/powder need to exert against the entire area of a case to expand a neck ~0.000000001"? I don't know, maybe 10psi depending on the case area and angles,, it ain't much. A folded piece of paper resting on the powder column would immediately jack the pressure this much. Engraving force is a little higher, so a bullet will not go far on primer firing alone, but it would be fully released here and travel for a moment.</p><p>If this process suddenly relied on overcoming bullet seating friction (pull force), primer firing would not move a bullet, and every gun in existence would explode on it's next firing with current powder loads..</p><p></p><p>Scenario #2; You FL size necks to leave something like 3thou interference.</p><p>Everything about this is excess, and causing extreme starting pressures, with extreme variances of that. Now you likely have a sized length of neck behind & smaller than seated bullet bearing. This, binding the base-bearing junction with forces including neck hardness, donut thickness, and shoulder angle. Such a neck would have to expand way way more (~2thou) before releasing a bullet. This is actually beyond expansion to outright upsizing.</p><p>Unless running an unerbore that relies on extreme starting forces, don't FL size necks. And you might as well stop downsizing necks so much that you're just re-upsizing them with bullet seating. This is not what bullets are for.</p><p></p><p>Crimping is unique. The neck would expand to release the bullet, but the bullet is still held back by the crimp(for a short period). In this case I'm sure the bullet has to overcome both the force and a friction of that crimp, or be held until the neck has upsized to clear the crimp from bearing. That's where you really need neck clearance.</p><p>I imagine the ballistic results would be similar to FL sized necks.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 1724912, member: 1521"] The scales of this internal ballistic process are extreme. Very small, very fast, very sensitive. Beginning with powder; If you load a shell case with primer/powder and no bullet, on firing you get WOMF. Fold a piece of paper and gently set it on top of the powder column,, on firing you get BOOM. With any real initial confinement you get POW. Confinement leads to pressure, and pressure speeds the powder burn. All powders are variable in burn rate, and potentially to either end of burn rate charts. On releasing of a bullet; With partial neck sizing no further than seated bullet bearing, and a bullet in place, the neck OD is cal + neck thickness. Necks are not 'squeezing' bullets, but resting against bullet diameter with only their spring back force. How far would a neck in this common scenario have to expand to freely release a bullet? REALITY: Difficult to measure with an electron microscope. Perhaps billionths of an inch. When folks claim you need ~2-3thou of neck clearance to be safe,, that's as likely analogous to 2-3ft on scale.. How much pressure would the primer/powder need to exert against the entire area of a case to expand a neck ~0.000000001"? I don't know, maybe 10psi depending on the case area and angles,, it ain't much. A folded piece of paper resting on the powder column would immediately jack the pressure this much. Engraving force is a little higher, so a bullet will not go far on primer firing alone, but it would be fully released here and travel for a moment. If this process suddenly relied on overcoming bullet seating friction (pull force), primer firing would not move a bullet, and every gun in existence would explode on it's next firing with current powder loads.. Scenario #2; You FL size necks to leave something like 3thou interference. Everything about this is excess, and causing extreme starting pressures, with extreme variances of that. Now you likely have a sized length of neck behind & smaller than seated bullet bearing. This, binding the base-bearing junction with forces including neck hardness, donut thickness, and shoulder angle. Such a neck would have to expand way way more (~2thou) before releasing a bullet. This is actually beyond expansion to outright upsizing. Unless running an unerbore that relies on extreme starting forces, don't FL size necks. And you might as well stop downsizing necks so much that you're just re-upsizing them with bullet seating. This is not what bullets are for. Crimping is unique. The neck would expand to release the bullet, but the bullet is still held back by the crimp(for a short period). In this case I'm sure the bullet has to overcome both the force and a friction of that crimp, or be held until the neck has upsized to clear the crimp from bearing. That's where you really need neck clearance. I imagine the ballistic results would be similar to FL sized necks. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Reloading
Neck Tension
Top