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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Powder Bridging for Kiwi Nate & Tang et al
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<blockquote data-quote="Kiwi Nate" data-source="post: 363955" data-attributes="member: 8533"><p>Well, I can qualify my 7mm RUM experiences as being consistant if thats any help. Thing is, this was a .200" freebore chambering rather than the factory .400" freebore. I forgot to mention this in the beginning and I am very sorry about this, I had forgotten. I am not one to BS people so- my bad.</p><p> </p><p>The range testing went like this (velocities are rounded to nearest 50fps):</p><p> </p><p>162gr SST 86gr Retumbo 3100fps</p><p>162gr SST 86gr Retumbo 3300fps bolt jammed.</p><p>I thought that I had stuffed up my reloading so fired another shot:</p><p>162gr SST 86gr Retumbo 3100fps</p><p>Then another:</p><p>162gr SST 86gr Retumbo 3300fps bolt jammed.</p><p>Went back to the bench, cleaned the scales (thinking that they must be sticking). Loaded another few rounds:</p><p>First shot 162gr SST 86gr Retumbo 3300fps bolt locked up. No further testing done at 86gr- lesson (finally) learned. </p><p> </p><p>Increased load to 90 grains Retumbo 3200fps. Max pressure, poor case life.</p><p> </p><p>Freebore was increased to .400" as per factory specs and I started again with 91 grains Retumbo. Muzzle velocity was 3235fps.</p><p> </p><p>Current pet load: 91gr Retumbo 180grVLD 3184fps. Groups .5MOA without brake, .3MOA with brake. I shoot it without the brake as I can't stand the noise and gas/ground debris blow back (spiral ports). </p><p> </p><p>As for H50BMG. 94 grains behind the 162 grain bullet yeilds 2800fps, safe load. Can only guess that it could be reduced to 91 grains for 2700fps with regard to testing 162-180 grain bullets at reduced velocities. Would still have to take a 300-400 yard shot to duplicate 1000 yard shots.</p><p> </p><p>It takes 102-104 grains of H50BMG to get the 7RUM up to pressure/ accuracy. Unfortunately, at these charge weights, its no different than hitting the bore with a gas cutting torch.</p></blockquote><p></p>
[QUOTE="Kiwi Nate, post: 363955, member: 8533"] Well, I can qualify my 7mm RUM experiences as being consistant if thats any help. Thing is, this was a .200" freebore chambering rather than the factory .400" freebore. I forgot to mention this in the beginning and I am very sorry about this, I had forgotten. I am not one to BS people so- my bad. The range testing went like this (velocities are rounded to nearest 50fps): 162gr SST 86gr Retumbo 3100fps 162gr SST 86gr Retumbo 3300fps bolt jammed. I thought that I had stuffed up my reloading so fired another shot: 162gr SST 86gr Retumbo 3100fps Then another: 162gr SST 86gr Retumbo 3300fps bolt jammed. Went back to the bench, cleaned the scales (thinking that they must be sticking). Loaded another few rounds: First shot 162gr SST 86gr Retumbo 3300fps bolt locked up. No further testing done at 86gr- lesson (finally) learned. Increased load to 90 grains Retumbo 3200fps. Max pressure, poor case life. Freebore was increased to .400" as per factory specs and I started again with 91 grains Retumbo. Muzzle velocity was 3235fps. Current pet load: 91gr Retumbo 180grVLD 3184fps. Groups .5MOA without brake, .3MOA with brake. I shoot it without the brake as I can't stand the noise and gas/ground debris blow back (spiral ports). As for H50BMG. 94 grains behind the 162 grain bullet yeilds 2800fps, safe load. Can only guess that it could be reduced to 91 grains for 2700fps with regard to testing 162-180 grain bullets at reduced velocities. Would still have to take a 300-400 yard shot to duplicate 1000 yard shots. It takes 102-104 grains of H50BMG to get the 7RUM up to pressure/ accuracy. Unfortunately, at these charge weights, its no different than hitting the bore with a gas cutting torch. [/QUOTE]
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