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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
preasure problems with 7 ultra
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<blockquote data-quote="NZ Longranger" data-source="post: 288732" data-attributes="member: 14"><p>Chris,</p><p>3284 fps with a 180gn Berger out of a 7mm RUM is over the edge unless you're running a 30" barrel? Out of the usual 26" barrel even in the sloppy factory chambers with the long throat 3200fps is about maximum. </p><p>If you're right on the edge pressure wise, the carbon build up and slight throat roughening as you fire progressively more rounds can push you over the edge, especially if the temperature is warmer as well.</p><p>Case length can be an issue, but most factory RUM chamber lengths are 2.875" or longer. Even a tight custom chamber will usually take brass 2.870" long with out spiking pressure. Don't trim until you've actually measured your chamber length, or you may trim too much.</p><p>Don't be put off the RUM, so long as you don't run it over the edge or expect to fire large numbers of rounds through it in rapid succession, it'll give superb long range performance with managable recoil that is hard to beat. I have built many 7mm/404's and 7mm RUMs and have never found them a problem to load for. I use mainly 2218/H50BMG powder and anywhere from 99 to 104 grains with the 180 Bergers and 175 SMK's depending on throat length. I have always got good barrel life when used in big game hunting situations. They are not varmint or match rounds, but a 180 Berger at 3200 fps out of a 26" barrel is a pretty darn good long range hunting performer!<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p>Greg</p></blockquote><p></p>
[QUOTE="NZ Longranger, post: 288732, member: 14"] Chris, 3284 fps with a 180gn Berger out of a 7mm RUM is over the edge unless you're running a 30" barrel? Out of the usual 26" barrel even in the sloppy factory chambers with the long throat 3200fps is about maximum. If you're right on the edge pressure wise, the carbon build up and slight throat roughening as you fire progressively more rounds can push you over the edge, especially if the temperature is warmer as well. Case length can be an issue, but most factory RUM chamber lengths are 2.875" or longer. Even a tight custom chamber will usually take brass 2.870" long with out spiking pressure. Don't trim until you've actually measured your chamber length, or you may trim too much. Don't be put off the RUM, so long as you don't run it over the edge or expect to fire large numbers of rounds through it in rapid succession, it'll give superb long range performance with managable recoil that is hard to beat. I have built many 7mm/404's and 7mm RUMs and have never found them a problem to load for. I use mainly 2218/H50BMG powder and anywhere from 99 to 104 grains with the 180 Bergers and 175 SMK's depending on throat length. I have always got good barrel life when used in big game hunting situations. They are not varmint or match rounds, but a 180 Berger at 3200 fps out of a 26" barrel is a pretty darn good long range hunting performer!:) Greg [/QUOTE]
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preasure problems with 7 ultra
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