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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Blew a Primer _ Analysis
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<blockquote data-quote="Pdvdh" data-source="post: 1389189" data-attributes="member: 4191"><p>Follow-up information, after additional inspection and analysis.</p><p></p><p>On <u>December 17, 2017</u>, I fired a new load (bullet and powder) in my 30/375 S.I. This cartridge is a Rich Sherman (user name <strong>elkaholic</strong>) improved cartridge design. The 375 Ruger is the parent case. The case is blown out with a 40 degree shoulder, and necked down to .308 caliber.</p><p></p><p>Components and load specifics of the 12/17/2017 testing are:</p><p></p><p>Casing: Hornady 375 Ruger</p><p>Primer: Federal GM215M</p><p>Powder: <strong>77.0</strong>gr Alliant Reloder 26</p><p>Bullet: 196.5 grain Badlands Precision - 0.010" jump until rifling contact</p><p>LabRadar MV: <strong>3192</strong>fps</p><p>Ambient Temperature: 30F</p><p>Consequence: I only fired one round because the casing web OD just forward of the rim expanded 0.0026" with this single firing. This load was over maximum pressure for the Hornady casing, based on that measured case web expansion. The primer remained in the primer pocket. No gases escaped the case head.</p><p>________________________________</p><p>On <u>January 15, 2018</u>, I tested MV with a lower powder charge.</p><p>All the above component and load specifics remained the same, except a different Hornady casing was used, and the powder charge was reduced.</p><p>The temperature was 5F colder than on December 17, 2017.</p><p></p><p>Casing: Hornady 375 Ruger</p><p>Powder: <strong>73.8</strong>gr Alliant Reloder 26</p><p>Temperature: 25F</p><p>LabRadar MV: <strong>3101</strong>fps</p><p>Consequence: A tiny wisp of smoke was noted. Upon removing the casing from the chamber, the primer was missing. The gas/smoke escaped the perimeter of the primer. I found the primer on the top of the magazine follower. The ID of the primer pocket measures 0.215", which is 0.006" - 0.007" greater than the ID of a new unfired Hornady case primer pocket. The OD of the fired Federal primer measures ~0.211". This cartridge which was charged with 3.2gr <em><strong>less</strong></em> Reloder 26 produced 91fps less MV.</p><p></p><p>The 1/15/2018 Hornady case was exposed to less pressure, producing less MV; all consistent with a powder charge 3.2gr less than the cartridge fired on 12/17/2017. Higher pressure and higher MV was produced in the 12/17/2017 case, yet it held its primer and no gas escaped the primer pocket.</p><p>The 1/15/2018 Hornady case web and primer pocket swelled ~twice as much as the 12/17/2017 case, resulting in the release of gas against the bolt face; even though the 1/15/2018 case was loaded with 3.2gr less Reloder 26.</p><p>_______________________________</p><p></p><p>Conclusion: The 1/15/2018 Hornady case head was 'softer', with a lower elastic yield strength than the 12/17/2017 Hornady case head. I'm unable to reach any other conclusion.</p><p></p><p>Further information: I had prepped four shells for an abbreviated ladder test with the LabRadar. The case that blew the primer was the lowest powder charge, and the only cartridge fired. Next day I pulled a bullet on the cartridge with the next higher charge of powder, and weighed the powder charge. Case was marked 74.6gr powder. Re-weighed the powder charge at 74.6gr. Spot on. Confirmed the powder looked exactly like Reloder 26. High confidence the 73.8gr case was correctly loaded with 73.8gr. Also, the lowered MV is consistent with the lesser powder charge, compared to the 12/17/2017 cartridge.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 1389189, member: 4191"] Follow-up information, after additional inspection and analysis. On [U]December 17, 2017[/U], I fired a new load (bullet and powder) in my 30/375 S.I. This cartridge is a Rich Sherman (user name [B]elkaholic[/B]) improved cartridge design. The 375 Ruger is the parent case. The case is blown out with a 40 degree shoulder, and necked down to .308 caliber. Components and load specifics of the 12/17/2017 testing are: Casing: Hornady 375 Ruger Primer: Federal GM215M Powder: [B]77.0[/B]gr Alliant Reloder 26 Bullet: 196.5 grain Badlands Precision - 0.010" jump until rifling contact LabRadar MV: [B]3192[/B]fps Ambient Temperature: 30F Consequence: I only fired one round because the casing web OD just forward of the rim expanded 0.0026" with this single firing. This load was over maximum pressure for the Hornady casing, based on that measured case web expansion. The primer remained in the primer pocket. No gases escaped the case head. ________________________________ On [U]January 15, 2018[/U], I tested MV with a lower powder charge. All the above component and load specifics remained the same, except a different Hornady casing was used, and the powder charge was reduced. The temperature was 5F colder than on December 17, 2017. Casing: Hornady 375 Ruger Powder: [B]73.8[/B]gr Alliant Reloder 26 Temperature: 25F LabRadar MV: [B]3101[/B]fps Consequence: A tiny wisp of smoke was noted. Upon removing the casing from the chamber, the primer was missing. The gas/smoke escaped the perimeter of the primer. I found the primer on the top of the magazine follower. The ID of the primer pocket measures 0.215", which is 0.006" - 0.007" greater than the ID of a new unfired Hornady case primer pocket. The OD of the fired Federal primer measures ~0.211". This cartridge which was charged with 3.2gr [I][B]less[/B][/I] Reloder 26 produced 91fps less MV. The 1/15/2018 Hornady case was exposed to less pressure, producing less MV; all consistent with a powder charge 3.2gr less than the cartridge fired on 12/17/2017. Higher pressure and higher MV was produced in the 12/17/2017 case, yet it held its primer and no gas escaped the primer pocket. The 1/15/2018 Hornady case web and primer pocket swelled ~twice as much as the 12/17/2017 case, resulting in the release of gas against the bolt face; even though the 1/15/2018 case was loaded with 3.2gr less Reloder 26. _______________________________ Conclusion: The 1/15/2018 Hornady case head was 'softer', with a lower elastic yield strength than the 12/17/2017 Hornady case head. I'm unable to reach any other conclusion. Further information: I had prepped four shells for an abbreviated ladder test with the LabRadar. The case that blew the primer was the lowest powder charge, and the only cartridge fired. Next day I pulled a bullet on the cartridge with the next higher charge of powder, and weighed the powder charge. Case was marked 74.6gr powder. Re-weighed the powder charge at 74.6gr. Spot on. Confirmed the powder looked exactly like Reloder 26. High confidence the 73.8gr case was correctly loaded with 73.8gr. Also, the lowered MV is consistent with the lesser powder charge, compared to the 12/17/2017 cartridge. [/QUOTE]
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