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Rebuilding my 375 RUM

 
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  #22  
Old 06-15-2013, 01:03 AM
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Join Date: Dec 2009
Posts: 856
Re: building a 375 h&h

No not enough said. Not even close. Hodgdon data IS pressure tested data. With a COAL of 3.6", a 300g bullet, and H4350, the listed max charge of 81.5g produces produces 49,500 CUP. See Hodgdon pressure tested data here:

Cartridge Loads - Hodgdon Reloading Data Center - data.hodgdon.com

The max pressure spec for the 375 H&H is 54,000 CUP. No matter how you slice it, the Hodgdon data is WAAAY below any possible danger level. At a 3.6" COAL, they couldn't even get enough powder in the case to come anywhere near max pressure as shown by the compressed designation of the load. I have no doubt that you already know this.

Are you really going to assert that a pressure level that is a full 4,500 CUP BELOW spec max is dangerous?

My handloads, using the Hodgdon max charge H4350, with a COAL of 3.750 (which was .080 from the rifling) and using a 300g Hornady BTSP would have produced even LOWER pressure than the Hodgdon book loads. For a detailed explanation of why, see the following:

Berger Article on Cartridge Overall Length and Base-to-Ogive Daily Bulletin

Your claim that .375 H&H brass is weak is also not backed up by any facts. The cartridge itself is spec'd for modern pressure with a max of 54,000 CUP or 62,000 psi. Virtually every modern magnum is based on the same case and has the same pressure spec or HIGHER. The Weatherby cartridges, based on the same case as the .375 H&H, are spec'd at 65,000 psi. Given your considerable experience, you know all of that already.

You are correct in stating that the cartridge was originally designed for optimum performance using cordite. At that time, the pressure spec was held to 47,000 psi. Original loadings from when the cartridge were introduced showed a 270g bullet @ 2650 and a 300g bullet @ 2500. Most factory loads today track closely with those numbers. Both SAAMI and CIP have since revised the max pressure spec upward considerably since then, following the post WWII availability of IMR propellants. For the most part, it does not appear that factory loadings have followed suit. No doubt you know all of this, as well.

I don't have 50 years of experience like you do. However, I do my homework on things like this before I ever start loading rounds. I follow published data and safe reloading practices. The results I have obtained from actual loading and chrono data track closely with published information, as well.

I have read many of your posts and, believe it or not, recognize and respect you as an experienced and generally level-headed fellow. It has not been my intent to personalize this, and I apologize if it appears otherwise.

Despite your experience, however, I am not prepared to believe that you know more than Bryan Litz, Hodgdon engineeers, SAAMI and CIP engineers, and Roy Weatherby combined. Likewise, I am not prepared to allow baseless and demonstrably false assertions to be passed off as fact, regardless of the experience level of the person making said assertions.

At no time has anyone on this thread suggested anything even remotely unsafe. Everything that has been discussed is in line with published and tested information. It is incorrect of you and irresponsible to claim otherwise.
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  #23  
Old 06-15-2013, 09:01 PM
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Join Date: May 2012
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Re: building a 375 h&h

Why would you quote hodgdon's data showing 4350 4,500 psi low when it is a compressed load and won't fit the case at any higher charge? I've tried; you will bulge the case walls with a higher charge and make a useless round of it. You are playing an apples and grapefruit game here.
If you think the factory loads aren't up to stuff you haven't touched off factories in your 375.
You DO have a 375 don't you??
Please tell me you aren't just quoting a loading book here. I've been shooting 375's for over 15 years and am on my second rifle at present. The data is for the most part correct. The case capacity limits pressures more than many rounds we are used to though. This round has more in common with a 308 win than a 300 win as far as what powders you should use.
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  #24  
Old 06-15-2013, 10:25 PM
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Join Date: Dec 2009
Posts: 856
Re: building a 375 h&h

Yes, I have fired factory ammo through my rifle and yes, I own a .375 H&H, which I have fired the referenced Hodgdon load through. I quoted the Hodgdon load for two reasons:

1) It has been the basis of experimentation that I have done (You know this. We have had a pretty good conversation regarding my efforts along those lines.).

2) To demonstrate that, when I used this same load data with a LONGER COAL, there is no way that I am pushing pressures or "hot rodding" with said load.

In that context, the "apples and grapefruit" statement is nonsensical. You DID read the ENTIRE thread, right?

My rationale for saying factory rounds are underloaded has been clearly laid out and the data speaks for itself. Relative to its potential, yes I believe the .375 H&H is underloaded by the factory. I understand why that is and I have stated as much.

Bottom line here is that people can have opinions all day long. No opinion trumps hard data to the contrary.
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  #25  
Old 06-16-2013, 04:15 PM
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Join Date: May 2012
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Re: building a 375 h&h

Benchracer, I've read the thread but haven't kept up very well here lately.
I thought you had a 375 but the names sometimes blur; sorry on that one.

The 4350's aren't that good in the 375 as they are too bulky- we've talked about that I think. Rl15, v540, 4895, and the like will get you to max. pressure with about any bullet. I do stand on the apples and grapefruit one though as even lawyered up hodgdon is at 50,000 to 51,000 cup with the powders that will actually make pressure. They could go up a grain or two at times but the extra 50 fps isn't going to do squat; you really need to step up in cartridge to get a meaningful gain here.
I haven't pushed any factories through a barrel with a strain gauge so I can't say with certainty that they are or aren't underloaded, but win 300 silvertips's were over 2500fps in my old win 375 and that's with crappy win ball powder. Given that they are intended for african climates where you can get well over 100 degrees I'm not thinking they are cream-puffing it too much.
In the end I'd rather have a 375 h@h at 2500 to 2600 fps with a 300 and let the bigger rounds hit it harder; I want my ammo to work anywhere I take the gun without building the loads for specific temp. ranges.
You do what you wish and have a good one. Apologies if I sounded a bit harsh on the last post.
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  #26  
Old 06-16-2013, 05:38 PM
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Join Date: Feb 2008
Location: North Dakota
Posts: 67
Re: building a 375 h&h

Good for you! The .375 H&H is a wonderful cartridge! I shot my PH's in South Africa last month for kicks(we were not hunting dangerous game). With open sights on his CZ we were banging targets at 400 meters. It was a pleasure to shoot. My next gun will be a .375 H&H!
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  #27  
Old 06-21-2013, 02:42 PM
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Re: building a 375 h&h

Well My OCD got the best of me with a little prodding from from a buddy... I am just going to rebarrel into a 375 ultra 26"+ brake... I have all the stuff and love the ultra... so I guess that is how im going to go now...I am a huge H&H fan but the ultra is just way too awesome to not do especially since I already have all the components
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Mike

Anything less than overkill is underachievement!

" Real elk guns start with the number 3 or bigger and blow two holes, one in and one out." - My Dad
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  #28  
Old 06-22-2013, 05:48 AM
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Join Date: Dec 2009
Posts: 856
Re: building a 375 h&h

Quote:
Originally Posted by Tikkamike View Post
Well My OCD got the best of me with a little prodding from from a buddy... I am just going to rebarrel into a 375 ultra 26"+ brake... I have all the stuff and love the ultra... so I guess that is how im going to go now...I am a huge H&H fan but the ultra is just way too awesome to not do especially since I already have all the components
The .375's have really grown on me since I bought my H&H. Regardless of the flavor, it is still good to see someone build a .375. Can't argue with a RUM flavored cartridge at all! It seems to me that the .375 diameter is just starting to have decent long range bullets made for it. I hope that trend continues. IMO, the .375's are so much more than just close range smashers.

Do you plan to use a faster twist than 1/12? I look forward to reading more details about your build.
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