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oneatatime
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Loading the 360 Nitro Express
Jul 20th, 2024 at 1:53am
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"360 Nitro Express" has a nice ring to it and is much easier to say than "38-55 with 300 grain bullets and maximum loads" which is our equivalent. Anyway, my Rigby is a 360 Nitro Express and it says so in so many words right on the top of the barrel at the breech. 360 2 1/4 inch case with 300 grain bullets and 30 grains of Cordite. 300 grains is 300 grains no need of translating. The twist of the barrel is fast to handle it (I think I measured it at 12). The actual groove diameter is .367+ and I got a 300 grain plain base mold from Accurate that looks like the original factory bullet and casts at .368+. I got a custom sizing die from S&S marked .369. I got a 38-55 Lyman M neck expanding die and chucked it in a drill press and filed it down to give me .001 neck tension and enough of a step to start a bullet. My brass is made from Norma 9.3x72R shortened to 2.25 inches and partially sized in an RCBS 9.3x72R die, neck expanded in a custom M die, and seated in a custom set 9.3x72R seating die (or possibly in a Redding 38-55 micrometer seater.) Bullets will be cast from 16 to 1. Federal LR Match primers will be used. A .370 Walter's Wad with .060 thickness will be seated under the bullet. Loading data will  be in next post.
  
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jhm
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Re: Loading the 360 Nitro Express
Reply #1 - Jul 20th, 2024 at 7:20am
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Very interesting... Sounds like something I would try and do. Right now my rabbit hole is an in process 38-72 Win. Borchardt. Then I got a Hepburn redo in 38-50 Rem. Pictures?



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oneatatime
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Re: Loading the 360 Nitro Express
Reply #2 - Jul 20th, 2024 at 11:13am
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JHM, pictures are up in the Single Shot Rifles section in the Greeley struck again! post.
  
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oneatatime
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Re: Loading the 360 Nitro Express
Reply #3 - Jul 20th, 2024 at 12:34pm
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Currently the designated perfect replacement for Cordite is Reloader 15 in the ratio of 1.19 R15 to Cordite. For my 30 grains Cordite this would be 35.7 grains of R15. This should match the original velocity and my rifle's sights and possibly at a lower pressure than the Cordite. When I found this out I quickly realized that R15 had vanished from the marketplace. While I was fretting over this and waiting for my mold to arrive it suddenly reappeared, of course at a much higher price! For my first tests I used some of the first bullets I had cast in the new mold at my usual 20 to 1 and Federal Large Pistol Match primers. On the cautious side I loaded the first rounds at about minus 20%, then 15%, then 10% and then a couple at 5%. I rounded this to 28 grains, 30 grains, 32 grains and 34 grains. All worked fine with the groups getting smaller, lower, and closer to the vertical line of the sights as I progressed. I was shooting at 50 yards (and my lowest sight is 100) so I knew they would end up a bit high. I kept a close eye on the fired primers as they were LP and the pressures were getting higher. The rifle has a large firing pin but it is well fitted to the block and has a nice contour. Based on all this I decided that for the next round of tests I would go to LR primers and cast at 16 to 1. We'll see. Now to cast.
  
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jhm
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Re: Loading the 360 Nitro Express
Reply #4 - Jul 20th, 2024 at 5:47pm
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You know I read the post a few days ago but didn't make the connection. Very nice rifle. Beautiful old school gun...



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oneatatime
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Re: Loading the 360 Nitro Express
Reply #5 - Aug 30th, 2024 at 7:26pm
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I loaded some of my 300 grain bullets with Reloader 15 loads that worked up to the levels of the original Cordite and shot at 100 to try to match the 100 yard fixed leaf on the rifle. I learned 2 things. One is that the Cordite load was a whomping, stomping load and the second is that the good old British wide V out there on the barrel and the bead front sight are more than a match for my old eyes at 100 yards. I've decided to see if I can find a more pleasant load that will shoot well, unless I need to knock a moose off his feet or something. I'll also dig out my variable aperture that clips on my glasses. Oh, the rifle handles the higher pressure of the Cordite level loads just fine. And I found another piece of information about the original owner that I posted in the "what you can find" thread in the General Discussion section.
  
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