458 Socom

[Fudmottin]

I know someone who does barrels for these. Unfortunately, my gun making budget for this year is over extended. But it might be a nice project for next year.

Who here has experience with it? How do you like it? Can you reach 500 meters?

I don't want the SBR hassle, so if I order a 458 Socom upper, it will have a 16 inch barrel. Does this hurt the load?

[Colohunter]

I was looking into these for awhile, but just built a 6.8. You would have a lot of drop out to 500 meters. I think the 16" would be fine, most people seem to like to shorter handier carbines in this cartridge. I think it is made more as a brush gun than a bench gun.

[Spook]

Yes you can get to 500,but the trajectory was more like artillery than a rifle. My guess is this cartridge was designed for close quarter combat rather than target of opportunity shooting.

[Fudmottin]

I'm not saying I would reach out to 500 all the time. That is mortar fire with any subsonic thanks to our friend gravity. Just the ability to do so would be nice though.

The reason for sticking with 16" is not just the SBR tax. Once a receiver is registered as an SBR, interstate transport becomes a big headache. I live very close to state lines and I do travel.

For the time being, silencers don't have that problem. Although I would have to rely on the GOPA because the surrounding states say nyet to them.

My 300-221 upper is a heck of a lot lighter than my 223 upper. I had the 223 done as a bench gun for long range shooting. The barrel of that weighs almost as much as the complete 300-221 upper.

I would expect a 458 Socom to be lighter still due to even more metal removed from the inside of the barrel.

[LouBoyd]

Just my opinions:
Long range subsonic shooting still requires low drag bullets. That's why the 300 Whisper is popular in the AR-15. It's about the heaviest low drag cartridge/bullet which can pass though an AR-15 magazine. The 338 Spectre can't handle the heaviest 338 bullets in an AR-15 magazine.
I own a 458 SOCOM RRA ar-15, and i don't consider it suitable for subsoinic shooting. It's fine as a short range hunting or urban entry rifle for bullets in the 90 to 350 grain range with standard supersonic loads.

The 458 SOCOM can be a great long range subsonic cartridge, but it needs at least a 30-06 length action and magazine. The Lehigh 582 grain 458 bullet is a good subsonic match for the case capacity of the 458 SOCOM That's the fifth cartridge in this picture:
http://i174.photobucket.com/albums/w108/ubvri/Ballistics/lehigh.jpg

[Fudmottin]

That puts a new spin on it. I guess one could go with a barrel on an Armalite AR-10 and get the action length of a 308. Still shorter than a 30-06 but close. That also makes it a much bigger project.

Could go with the DPMS LR308 too I guess.

Still, I think I'm probably going to pass. Leave that round for more serious people. If I was going to get that serious (hey, it's a new gun not just an upper), I guess I would skip over the SOCOM and go for one of the .510 wildcats if they don't go banning 50 caliber. I wonder how an AR-10 shooting a 50 caliber round would go over at the range.

[d-mon]

Hi,
What kind of barrel twist would be suitable to stabilize up to 500gr subsonic bullets of basic shape ie. flar base round nose?
I am just about to place an order for a barrel and want to make sure.

many thanks.
Nick

[Spook]

14 works for a typical jacketed 500 gr but the heavier /longer Lehighs require a 10

[LouBoyd]

I've bought an 8" twist Pac-Nor barrel to make a bolt action specifically for shooting the 582 grain Lehigh solid. The McGyro program says 10" might work but I wanted to be safe. 8" should be stable even transsonic at the elevation I shoot (mile+) 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.

[HUNTER2]

Isn't the 458 x 2 real close to the 450 marlin? Benifits of each?

[d-mon]

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

[LouBoyd]

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.

[d-mon]

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

[LouBoyd]

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.

[d-mon]

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

[blasternaz]

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

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.