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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
preasure problems with 7 ultra
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<blockquote data-quote="Pdvdh" data-source="post: 288578" data-attributes="member: 4191"><p><strong>Re: pressure problems with 7 ultra</strong></p><p></p><p>Yes, excess case neck length can increase pressure if the case neck bottoms out on the throat in the end of the chamber and consequently gets swaged down onto the bullet - because the bullet is then pinched tightly into the case and can't blast free as easily at the moment of ignition. But measure the case neck length in the chamber before you trim them back too far. Don't know what model rifle you're working with, but my two Tikka T3s both came with 0.050" excess neck (above and beyond maximum case length) reamed into the chambers from the factory. They probably do this as a safety precaution so reloaders don't blow up their rifles if they fail to keep the case necks trimmed back. As a consequence I only trim to even up the case neck lengths. My Tikka chambers are both 7mm Rem Mags.</p><p></p><p>That barrel may have the problem Michael expressed. He's gone through two 300 RUM barrels and has convincingly demonstrated the throat erosion & increasing pressure phenomenon. He shoots a heck of a lot and keeps detailed records. Like he said - the 7mm RUM will likely erode throats faster than his two 300 RUMs did.</p><p></p><p>Keep us posted? I'd like to hear how this turns out as you investigate the cause(s).</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 288578, member: 4191"] [b]Re: pressure problems with 7 ultra[/b] Yes, excess case neck length can increase pressure if the case neck bottoms out on the throat in the end of the chamber and consequently gets swaged down onto the bullet - because the bullet is then pinched tightly into the case and can't blast free as easily at the moment of ignition. But measure the case neck length in the chamber before you trim them back too far. Don't know what model rifle you're working with, but my two Tikka T3s both came with 0.050" excess neck (above and beyond maximum case length) reamed into the chambers from the factory. They probably do this as a safety precaution so reloaders don't blow up their rifles if they fail to keep the case necks trimmed back. As a consequence I only trim to even up the case neck lengths. My Tikka chambers are both 7mm Rem Mags. That barrel may have the problem Michael expressed. He's gone through two 300 RUM barrels and has convincingly demonstrated the throat erosion & increasing pressure phenomenon. He shoots a heck of a lot and keeps detailed records. Like he said - the 7mm RUM will likely erode throats faster than his two 300 RUMs did. Keep us posted? I'd like to hear how this turns out as you investigate the cause(s). [/QUOTE]
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preasure problems with 7 ultra
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