458 Socom load data

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Capt45 posted this 25 October 2017

Looking for some load data for a Ohas 45-405F.  These as cast with Lyman #2 weigh approx 430gr.  

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Ed Harris posted this 25 October 2017

If you carefully measure water capacity of the case with bullet seated, I think you will find that the .458 SOCOM compares very closely to the .45-70.  You would probably not get into any trouble using pressure tested load data from reliable sources, such as Speer No. 13 or No. 14, for the same weight bullet, adjusting the powder charge in direct proportion to their relative case capacities. Reduce the charge for the smaller case, and stick to starting loads listed for the 1895 Marlin or 1886 Winchester until you have established that the rifle functions OK, then work up carefully using a chronograph not exceeding the measured velocity of factory loads, if any exist for the SOCOM. 

Not a perfect solution, but the AR is a stronger platform than a Marlin 1895 Lever action or Winchester 1886 you would be using as source data.  While QuickLoad might yield a useful solution, I prefer to work up accurate loads which function the rifle reliably, carefully adjusting charge in proportion to measured case capacity using known pressure tested data in the closest available cartridge as a baseline. That method has worked with a great variety lot of experimental stuff and I haven't blown myself up yet.

If you get good function and accuracy without obvious pressure signs, you are way ahead of the game. 

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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Capt45 posted this 25 October 2017

Thanks Ed, now the journey begins.

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joeb33050 posted this 25 October 2017

START AT 10/UNIQUE, GO UP 1/2 GRAIN AT A TIME, LOOK FOR PRESSURE SIGNS , FUNCTION AND ACCURACY.

joe b.

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Ed Harris posted this 25 October 2017

If this is a .458 SOCOM built on an AR platform Unique probably isn't going to cycle the gun within safe pressure. 

I would opt for a powder in the burning rate range of IMR4198, RL7 or IMR3031.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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Capt45 posted this 25 October 2017

I have the 4198 and the 3031.

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Ed Harris posted this 26 October 2017

I would be inclined to try a "Trapdoor" load, about 40 grains of 3031 first and see if the gun cycles, then work from that.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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Capt45 posted this 26 October 2017

Probably get on that tomorrow Ed, have to take the wife to the doctor @1:00 then drive 100 miles to pick up the granddaughter at the airport @ 110 tonight.  Life ALWAYS seems to get in the way.

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joeb33050 posted this 26 October 2017

If this is a .458 SOCOM built on an AR platform Unique probably isn't going to cycle the gun within safe pressure. 

I would opt for a powder in the burning rate range of IMR4198, RL7 or IMR3031.

I believe, based on what I see at the range here in Florida, that UU grains of Unique will safely (but uncomfortably) cycle = extract/eject/chamber an AR15 style rifle; perhaps with some adjustment.

But,

Why would anyone want or need  to fire a 430 grain bullet out of a rifle faster than the gun could be cycled manually? If the zombies are coming, fire jacketed. We're talking pain here.

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joeb33050 posted this 26 October 2017

If this is a .458 SOCOM built on an AR platform Unique probably isn't going to cycle the gun within safe pressure. 

I would opt for a powder in the burning rate range of IMR4198, RL7 or IMR3031.

Or we could go to the internet:

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Capt45 posted this 26 October 2017

Why would anyone want or need  to fire a 430 grain bullet out of a rifle faster than the gun could be cycled manually?

Sorry, thought this was a cast bullet site.  I do it because I like to do it and it's considerably cheaper than the jacketed counterpoint.  I'm not wanting to sling this chunk of Lead supersonic, I want to push it sub sonic.

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Ed Harris posted this 27 October 2017

Joe, 

The breech pressure load table you posted tells us absolutely nothing about port pressure, which is critical to semi-auto function of his rifle. 

I don't know exactly where the gas block on his .458 SOCOM is located, but can say with some experience and relative assurance, based on the M16A2 and M4, that if peak CHAMBER pressure with BE is over 30 kpsi that about halfway down the barrel or so where the gas is drawn off to cycle the action, PORT pressure is probably going to be way below the 15,000+/-1,500 which is the design spec for the M4, and I'll stand by that unless you happen to have put a transducer down there to measure and can give us some hard numbers... 

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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Capt45 posted this 27 October 2017

Ed;

My upper is a Tromix that was purchased already built and I don't know much about it other than the price.  Right now my grandson has it and we are going to work up some loads this weekend.

Thanks for all your input.

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joeb33050 posted this 27 October 2017

Joe, 

The breech pressure load table you posted tells us absolutely nothing about port pressure, which is critical to semi-auto function of his rifle. 

I don't know exactly where the gas block on his .458 SOCOM is located, but can say with some experience and relative assurance, based on the M16A2 and M4, that if peak CHAMBER pressure with BE is over 30 kpsi that about halfway down the barrel or so where the gas is drawn off to cycle the action, PORT pressure is probably going to be way below the 15,000+/-1,500 which is the design spec for the M4, and

I'll stand by that unless you happen to have put a transducer down there to measure and can give us some hard numbers... 

Do you have a transducer, Ed? Do you have a source for this, or is it another opinion? Tell us how you know, Ed! Is this another bullet hardness/pressure imaginary fact like you and Mr. Davis started, oh so many years ago?

It was fairly quick to do it all in Quickload, once everything was set up for the cartridge, barrel length and bullet. It's just a matter then of selecting the powder in the drop down menu and changing the load. Since I would have to type in the info here, I thought it would be just as time efficient to type in a table in Open Office and make that a graphic file to post here. You can save the table graphic below and have the info without copying anything, by right clicking on it and save image.

Burn rate is from the IMR website. http://www.imrpowder.com/burn-rate.html

Image

Satisfactory powders for 458 Socom subsonic: Bullseye, Unique, 2400

Unsatisfactory powders:
1. Red Dot and Green Dot because at max chamber pressure, they yield velocities below your desired 1050 fps.

2. H322 because only 73.3% burn in barrel, and if a supressor is used it will fill up with unburnt powder. Same with 4831 with 37.4% burn in barrel, and IMR 4064 with 66.9% burn in barrel. These powders are all too slow.

3. Trailboss because with 100% fill, you can only get 832 fps; you cannot get enough in the case to work with this cartridge.
_________________
You can fool all of the people some of the time, and some of the people all of the time...and those are pretty good odds.

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joeb33050 posted this 27 October 2017

Any questions?

joe b.

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Capt45 posted this 27 October 2017

Joe;  of the pwds you've listed, I have most of them.  I am looking more at the 2400 at this time.  Hope to load some this weekend.

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Ed Harris posted this 27 October 2017

Joe, when I was employed in Ruger's engineering dept. at the Newport facility from 1984-87 I supervised thousands of rounds being fired in combination breech and port pressure tests of both 5.56mm and 7.62x39 ammunition in which the gas ports were located at various distances from the breech.  This testing pre-dated tranducer standardization, so was all done with radial copper using the government methods which were standard at the time. The purpose of the testing was to determine the best placement for the gas block in the AC556K SMG and an experimental 7.62x39 platform under development at that time.  Previously I had assisted in similar tests conducted at MCDEC, Quantico, VA during the development and operational testing of the M4 carbine. 

While I do not currently have access to such test equipment, during the years I did so for a living, as my primary occupation, I learned a bit about the time/pressure and bullet travel distances and adiabatic expansion characteristics of various propellants as well as the port pressures required to accelerate a mechanism to provide reliable semi-auto function and a sustainable cyclic rate.  I don't care to get into along distance urinating contest with you, but am simply trying to answer a reader's question based on my experience.  I consider the matter closed.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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