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My new .300 RUM
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<blockquote data-quote="Mark_in_utah" data-source="post: 7314" data-attributes="member: 1503"><p>Since I just got a 700 LSS in .338 RUM, and I've been going through the process breaking of it in and working up loads, I can share a few observations:</p><p></p><p>1. Your cases might be getting squashed because there is no chamfer in the factory cases. Take your little tool and chamfer the inside of the mouth just a tad. My factory cases were nice, but still had a few questions when loading them up for the first time. Once I started chamfering the mouths, which is normally not a big concern, the force to seat the bullet dropped in half. It was an unusual occurance.</p><p></p><p>2. My factory barrel was ROUGH! I had 160 rounds down the barrel and it was still fouling really bad and the accuracy wasn't all that great. That was after pillar bedding the laminated stock, floating the barrel, and adjusting the trigger to 3 pounds, AND installing a Vais brake and re-crowning the muzzle. My 'smith scoped the bore and the last half of the barrel was STILL very rough. I talked to a guy that had a .300 RUM that had the same problems. Very rough bore and poor accuracy. He had his barrel lapped and it solved the problem. I ended up fire lapping my barrel using Tubbs Final Finish. Check it out, it works well. Now it's shooting well.</p><p></p><p>3. The factory crown was BAD! The factory tool chattered on the crown. Not a pretty sight. Check it over closely.</p><p></p><p>I'm now getting a 9/16" pattern, which is a ragged hole with this using 250 grain GameKings and 83.2 grains of IMR4831 scooting along at 2859 fps. I got up to 3004 fps, but the accuracy wasn't there.</p><p></p><p>The loading charts are very conservative. I ran out of space using WC872. 104 grains is a compressed load, and is about the same speed as H870 or H1000. I've put up to 93 grains of WC852 (mil-surp 4831) and got 3077 fps. So far no visible pressure signs. Your .300 may like slower powders more, but don't be afraid to give 4831 a try.</p><p></p><p>4. Plan on bringing a towel soaked in ice water to the range to cool the barrel. I can get off about 20 rounds an hour and keep the barrel cool enough to hold with my hand. Shoot 5 shots, wrap in cold towel, clean barrel if needed. When cooled, shoot 5 shots and cool it down again.</p><p></p><p>5. Recoil will be about double that of a 7 mag. Plan on it. Take the appropriate precautions. A 10 pound bag of lead shot I've heard does wonders. My brake works well for me.</p><p></p><p>Have fun and burn LOTS of powder!</p><p></p><p>Mark in Utah</p></blockquote><p></p>
[QUOTE="Mark_in_utah, post: 7314, member: 1503"] Since I just got a 700 LSS in .338 RUM, and I've been going through the process breaking of it in and working up loads, I can share a few observations: 1. Your cases might be getting squashed because there is no chamfer in the factory cases. Take your little tool and chamfer the inside of the mouth just a tad. My factory cases were nice, but still had a few questions when loading them up for the first time. Once I started chamfering the mouths, which is normally not a big concern, the force to seat the bullet dropped in half. It was an unusual occurance. 2. My factory barrel was ROUGH! I had 160 rounds down the barrel and it was still fouling really bad and the accuracy wasn't all that great. That was after pillar bedding the laminated stock, floating the barrel, and adjusting the trigger to 3 pounds, AND installing a Vais brake and re-crowning the muzzle. My 'smith scoped the bore and the last half of the barrel was STILL very rough. I talked to a guy that had a .300 RUM that had the same problems. Very rough bore and poor accuracy. He had his barrel lapped and it solved the problem. I ended up fire lapping my barrel using Tubbs Final Finish. Check it out, it works well. Now it's shooting well. 3. The factory crown was BAD! The factory tool chattered on the crown. Not a pretty sight. Check it over closely. I'm now getting a 9/16" pattern, which is a ragged hole with this using 250 grain GameKings and 83.2 grains of IMR4831 scooting along at 2859 fps. I got up to 3004 fps, but the accuracy wasn't there. The loading charts are very conservative. I ran out of space using WC872. 104 grains is a compressed load, and is about the same speed as H870 or H1000. I've put up to 93 grains of WC852 (mil-surp 4831) and got 3077 fps. So far no visible pressure signs. Your .300 may like slower powders more, but don't be afraid to give 4831 a try. 4. Plan on bringing a towel soaked in ice water to the range to cool the barrel. I can get off about 20 rounds an hour and keep the barrel cool enough to hold with my hand. Shoot 5 shots, wrap in cold towel, clean barrel if needed. When cooled, shoot 5 shots and cool it down again. 5. Recoil will be about double that of a 7 mag. Plan on it. Take the appropriate precautions. A 10 pound bag of lead shot I've heard does wonders. My brake works well for me. Have fun and burn LOTS of powder! Mark in Utah [/QUOTE]
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