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- - 458 Socom (http://www.quarterbore.net/forums/showthread.php?t=2360)

Thanks Louboyd and spook for the information.
When I contacted pacnor regarding the twist rate, they suggested 1in 8", but obviously it is for the lehigh bullets that I am not going to use because not available in NZ.
I hesitate between the 1 in 14" or th 1 in 13" that might help to make sure things are just right. The 1 in 13" is a 3 grouves barrel, is there any difference with the 6 or 8 grouves ones? for shooting jacketed or cast bullets?

Please Louboyd, keep us posted with your results, that sounds very interesting.

Nick

458 cartridges for heavy low drag subsoics.

These are all are similar in performace in order of case capacity.
cartridge h20 length max-psi case type head
450 Marlin 79.0 2.080 47862 belted mag 458 WM
458x2 Amer 73.0 2.000 59988 belted mag 458 WM
458 Socom 61.6 1.573 35000 rebated 308
458 Whisper 60.0 1.750 45873 belted mag 460 Wby

All have good and bad points. For my experiments I want a high pressure rating. The SAAMI ratings are more for the type of firearm they're expected to be used in than any limitation of the brass. I didn't believe the 458 Socom or 458 Whisper would feed from a Rem 700 magazine very well either. It was the availability of dies and reamers that made the final decision for me.

I have the reamer, the brass and the dies, the bullets;
I just need the barrel and to choose what action to go with...

Nick

Quote:

Originally Posted by d-mon (Post 12061)

I have the reamer, the brass and the dies, the bullets; I just need the barrel and to choose what action to go with...
Nick

What specific bullets do you plan to shoot. Where do you shoot (elevation and temperature) That will determine twist rate.
Do you plan to use a suppressor? Do you care how loud it will be? Do you wish to also be able to shoot supersonic. That will determine barrel length.

You can buy a prefit barrel from Pac-Nor (and perhaps other barrel manufacturers) in a wide choice of twists with everything done but chambering. Bolt actions without extractor cuts are the easiest to fit. A Rem 700 or Post 64 Win 70 is easy to work with. Pick one with a 308/30-06 bolt face. If you want an AR-15 just buy one from Rock River Arms. It's already chambered in 458 Socom. Single shots are usually more diffcult to barrel than bolt actions because of the extractor work.

Hello Lou boyd,

i intend to use subsonic ammos mainly, with a silencer, and intend to shoot bullets no bigger than hornady's 500gr round nose.

Altitude is going to vary a lot, as I am in New Zealand and one day you can hunt at 200m and the next at 1200m.

I will get just a contoured barrel blank as I have the tooling and experience to fit properly on an action.

As action choice: winchester post 64, howa, and remington would be the first 3 one I am thinking about, because angled rail are easy to get for them.
I also thought about shortening a mauser action down to the right size for the 458 socom and feeding from a ruger mini 14 mag.

I do not really see the extractor problem with single shot action???
omark or barnard action haven't got an extractor cut on their barrels.

thanks.

Nick

I assume this is based on the 458 WM? Seems like a larger bore version of our old "2 x 4" round for deer hunting in the WI swamps and heavy timber. WW '94 rebarreled to .40 and cartridge opened up to and trimmed to 2 inches. long time ago...
Sounds like a nice project, please keep us informed of your results.

Blasternaz

Quote:

Originally Posted by LouBoyd (Post 12035)

It will be on a Rem 700 Long action using a 458X2 American cartridge (sixth in the row shown above). I haven't finished it so I can't tell you whether it will even shoot.

I chose the 458x2 over the 458 Socom because it has a much higher pressure rating. I'm of the opinion (but no solid proof) that fast burning high pressure minimum volume loads (within reason) for subsonics give low muzzle pressure and (most important) the smallest velocity dispersion. I'll find out if that's true with this beast. It will be a 16" barrel (to be legal). 10" would be a bit better ballistically. I'll experiment with lubrication to minimize bore friction. That may or may not prove to give better velocity uniformity but I expect it will.

Practical use? None. I'm only interested in learning about ballistics.