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Posted: 8/20/2026 12:02:59 AM EDT
[Last Edit: lazyengineer][Edited]
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A friend is getting into reloading, to feed this beast. I've never loaded anything in that class, so handling such huge casings and powder charges and power levels, is past my current experience base. Any nuances or aspects or things I should watch for? |
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Ive dealt with my share of magnum cartridges over the years. I load a fair bit of 300 PRC with H1000, Retumbo and N570. I use Fed GMM LRMs or CCI 250s, Lapua brass, and shoot mostly 220 Bergers and SMKs. 300 RUM is pretty much the same as loading 300 PRC, just bigger. No belt to deal with, which is good. Use the correct powders, probably nothing faster than something like H1000. Match bullet to whatever twist rate he has. If he has a 8 or 9 twist, pretty much anything all the way up to 250gr bullets is doable, but 220s are a real sweet spot unless youre getting out there. Buy decent brass, Peterson or ADG. Be aware ADG generally has lower case volume because its a thicker case. Start at 20 thou off the lands. Primers will need to be a magnum for sure. And if he wants to shoot it alot? Order a barrel blank right away... 
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Originally Posted By lazyengineer: Usage will mostly be 1000 gong range, for starters at least What is barrel life like? I'll check on primers - i might not have magnum, but will look. He picked up a 8lb keg of MP703-1 (MagPro). And 250 count of 220gr SMK 220 SMKs are a good bullet if you just want to bang steel at a grand. Barrel life is probably 1500ish rounds. Magnum primers are a must. Mag Pro will work fine, but dont expect it to be laser accurate. If you plan on shooting the gun in 80 degree weather? Do your load dev in 80 degree weather. This is why I use temp stable powders. The per shot cost on the large magnums dictates to me that I need to make everything as accurate as I can. You have to consider that at a 1500 round lifespan on the barrel itself, you are blowing 50 cents worth of barrel out the end of it every time you touch one off as well. |
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I agree with Kaldor, if he truly wants best performance and best barrel life, he has to pick carefully what his load is and how he shoots it...My go to for powder for LR stuff is the 230 grain Berger H/T loaded on top of a RP 9.5 magnum primer, and 99.0 grains of Accurate RL-33 powder....That produces 3220FPS, 5295 ft.lb. energy....It is sub MOA easily....I've averaged 1600 ads per barrel on Barlein barrels, before they go over 1 MOA, the key is not trying to push velocity or fire rate..3-5 rds and the barrel will be smoking hot... My honest opinion, the 230/245/250 grain bullets may not be the best choice for the RUM, the more wind you fight the better the heaviest bullets work, but I find the 230 better for me than the 245/250, I think the 220 Berger may work even better than the 230 but I have not tried any yet.. Brass wise, All I currently use is RP brass since I have so much of it from years of buying when ammo was cheap, but ADG/Norma/Nosler have all been widely reported as tier 1 brass for the RUM... everything else I would avoid personally, most will eat primer pockets like a crack whore, especially Hornaday...If I had to buy brass today, I would try Norma brass, its widely available, it has been extremely consistent, high quality brass in other calibers I use it in like 375H&H, 6.5CM and 30-06.....ADG brass is great, but expensive and It has to be carefully worked up because it is slightly less capacity due to thickness I have heard... Go to powders are retumbo and H-1000 for lighter stuff, H869 and RL-33 and such for the heavies..I have tried most of the powders made over the years, my go to is normally one of these 4 depending on bullet...You want the slowest of slower powders, and accuracy and velocity can be far different in very similar powders, only way to know is work up a load and see what they do in your rifle...Loading long is also very helpful in the RUM, I currently load the 230 to just a hair under 4.00" versus the SAAMI spec length of 3.60".. Of course that means it is single feed unless you can use Wyatt's extended CFE-9 internal magazine setup, but it won't fit most aftermarket actions....If he does his part, the cartridge is capable of very impressive stuff, it all comes to him mastering the cartridge..Ask away, any questions you have, on the load or on shooting it and one of us can help with it, I've only taken mine out to 2000 yards, I want to push it one of these days, just gotta find the time to go do it... |
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Originally Posted By AKSnowRider: I agree with Kaldor, if he truly wants best performance and best barrel life, he has to pick carefully what his load is and how he shoots it...My go to for powder for LR stuff is the 230 grain Berger H/T loaded on top of a RP 9.5 magnum primer, and 99.0 grains of Accurate RL-33 powder....That produces 3220FPS, 5295 ft.lb. energy....It is sub MOA easily....I've averaged 1600 ads per barrel on Barlein barrels, before they go over 1 MOA, the key is not trying to push velocity or fire rate..3-5 rds and the barrel will be smoking hot... My honest opinion, the 230/245/250 grain bullets may not be the best choice for the RUM, the more wind you fight the better the heaviest bullets work, but I find the 230 better for me than the 245/250, I think the 220 Berger may work even better than the 230 but I have not tried any yet.. Brass wise, All I currently use is RP brass since I have so much of it from years of buying when ammo was cheap, but ADG/Norma/Nosler have all been widely reported as tier 1 brass for the RUM... everything else I would avoid personally, most will eat primer pockets like a crack whore, especially Hornaday...If I had to buy brass today, I would try Norma brass, its widely available, it has been extremely consistent, high quality brass in other calibers I use it in like 375H&H, 6.5CM and 30-06.....ADG brass is great, but expensive and It has to be carefully worked up because it is slightly less capacity due to thickness I have heard... Go to powders are retumbo and H-1000 for lighter stuff, H869 and RL-33 and such for the heavies..I have tried most of the powders made over the years, my go to is normally one of these 4 depending on bullet...You want the slowest of slower powders, and accuracy and velocity can be far different in very similar powders, only way to know is work up a load and see what they do in your rifle...Loading long is also very helpful in the RUM, I currently load the 230 to just a hair under 4.00" versus the SAAMI spec length of 3.60".. Of course that means it is single feed unless you can use Wyatt's extended CFE-9 internal magazine setup, but it won't fit most aftermarket actions....If he does his part, the cartridge is capable of very impressive stuff, it all comes to him mastering the cartridge..Ask away, any questions you have, on the load or on shooting it and one of us can help with it, I've only taken mine out to 2000 yards, I want to push it one of these days, just gotta find the time to go do it... Good info here! My 300 PRC is the same for heat. I shoot some informal leagues, and every now and then I bring it out for fun. We have to shoot 10 for score. If I shoot too quickly, the barrel is smoking hot, so I have to cadence myself to shoot a round about every 45 seconds to not overheat the barrel so much. Im pushing 220 Bergers at 3050 from a 30" barrel with N570. I single feed mostly, but when I use mags I use AICS 300 RUM mags which allow for a 3.750 OAL. Kudos to Manners for cluing me in on that one when they made my stock. You would definitely need a custom stock to handle that Wyatts setup, but a 4" OAL is massive! |
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I'm shooting Retumbo and 7825SSC (can't find any more) under Barnes 200gr LRX Rifle is shooting under MOA @ 100 ,strings a little vertically if you shoot fast. Speeds are beyond Barnes load recomendations as are powder charges but no pressure signs in my rifle. She weighs 10lbs 9oz with glass and chassis so not too hard to shoot with the brake or suppressed. Easily rings steel @ 1K  ,Nice cloveleafs @ 600yrds.
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Originally Posted By Kaldor: Good info here! My 300 PRC is the same for heat. I shoot some informal leagues, and every now and then I bring it out for fun. We have to shoot 10 for score. If I shoot too quickly, the barrel is smoking hot, so I have to cadence myself to shoot a round about every 45 seconds to not overheat the barrel so much. Im pushing 220 Bergers at 3050 from a 30" barrel with N570. I single feed mostly, but when I use mags I use AICS 300 RUM mags which allow for a 3.750 OAL. Kudos to Manners for cluing me in on that one when they made my stock. You would definitely need a custom stock to handle that Wyatts setup, but a 4" OAL is massive! Yes, loading really long is the way if you really want to push performance..when I was working up the original 230 load, I went all the way up to 3348 fps velocity, before starting to see pressure, but accuracy wasn't quite as good plus it would have only been a hunting load for under 55 temps, since anything higher would have gotten into pressure...The Wyatts setup is the setup for a internal magazine, I run a chassis and use accurate mags 300rum CIP 3.850" mags... This pic shows the 3.600" SAAMI length compared to the 3.850" CIP mag I load point blank bear rounds(200barnes LRX @ 3.775") and my hand feed 230 grain Berger @ 3.975".. Attached File Accurate 3.850" CIP mag with 200 grain Barnes LRX loaded to fit... Attached File |
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