AR Sponsor
Posted: 5/18/2011 8:59:49 AM EDT
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Looking to buy a 458 socom upper soon and would like some setup ideas. Would appreciate any pictures you may have to post.
Thank you. |
...it belongs to one of the members who frequents the retro forum
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Here are my three ARs and the pistol:
16 inch heavy barrel .936 at port with CAR gas, 14 inch DD Lite rail: 
20 inch woody, .750 at port with midlength gas: 
12.5 inch SBR, .750 at port with handgun gas, DD 12 inch lite rail: 
And you don't have to stick with the AR platform: 14 inch Savage Striker: 
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Very nice 
Thank you |
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Velocities with the .458 SOCOM are almost all the same regardless of barrel length. Of the 3 of my 4 that I have measured, the fastest is the 14 inch bolt action handgun by just a few FPS. The 16 inch is only a few FPS faster than the 12.5 inch.
The dreams of getting 2500 fps using a 24+ inch barrel are just that, dreams. 16 inches is more than enough to get 99% of the velocity out of the .458 SOCOM. Also note that all barrels are Pac-Nor stainless. And you may be surprised to find that differing rifling twist do not mean a whole hell of a lot either no matter what some may claim. Note that the barrel that should be the slowest is in fact the fastest. 1:18 is supposed to give the highest velocities but in mine, t'ain't so. Here are the actual measurements taken on the same day, same loads, 15 feet from the muzzle: 300 gr. TTSX H110 31.5 gr. 12.5 inch, handgun gas, 1:14 twist = 1649.0 fps 14 inch bolt action pistol, no gas, 1:14 twist = 1685.6 fps 16 inch, CAR gas, 1:18 twist = 1666.7 fps. |
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Quoted: Velocities with the .458 SOCOM are almost all the same regardless of barrel length. Of the 3 of my 4 that I have measured, the fastest is the 14 inch bolt action handgun by just a few FPS. The 16 inch is only a few FPS faster than the 12.5 inch. The dreams of getting 2500 fps using a 24+ inch barrel are just that, dreams. 16 inches is more than enough to get 99% of the velocity out of the .458 SOCOM. Also note that all barrels are Pac-Nor stainless. And you may be surprised to find that differing rifling twist do not mean a whole hell of a lot either no matter what some may claim. Note that the barrel that should be the slowest is in fact the fastest. 1:18 is supposed to give the highest velocities but in mine, t'ain't so. Here are the actual measurements taken on the same day, same loads, 15 feet from the muzzle: 300 gr. TTSX H110 31.5 gr. 12.5 inch, handgun gas, 1:14 twist = 1649.0 fps 14 inch bolt action pistol, no gas, 1:14 twist = 1685.6 fps 16 inch, CAR gas, 1:18 twist = 1666.7 fps. Why do you think that is? Is a bolt gun inherently faster than a gas gun? |
| The first gut reaction answer is the lack of gas being pulled off to operate the action. The honest answer is no idea really. If I were to give you what I think is the honest answer it would be that is it just barrel to barrel differences. Even though all are Pac-Nor stainless barrels, seeing barrel to barrel differences in velocity such as this between two seemingly identical barrels is extremely common. The velocity spread I am seeing between the different barrels is well within the shot to shot ES of the loads. Seeing a 20 to 30 fps ES is extremely common and if I were a betting man, I'd wager that the difference is due to just that, barrel to barrel differences, not twist, length, or lack of a gas port. |
| My woody is a midlength. A middy does not look much if any different than a CAR or rifle. While my woody has a rifle front sight the midlength GB is hidden under the forend, but it is still a middy gassed firearm. Do be aware that midlength gas systems in the .458S can cause functioning trouble. Some SBR and CorBon loads will not function reliably in a midlength gas nor will H110 loads many times. My CAR and handgun gassed rifles function flawlessly with H110 but the midlength gas will not run at all. H110 is too fast and the pressure curve is not correct for midlength gas, but switch over to the slightly slower Re #7 and the midlength runs like a bat out of hell, and Re #7 will also work just fine in the handgun and CAR length gas systems, although it does not give quite the velocity in the 12.5 and 16 inch rifles or 14 inch handguns as does H110. |
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Quoted:
My woody is a midlength. A middy does not look much if any different than a CAR or rifle. While my woody has a rifle front sight the midlength GB is hidden under the forend, but it is still a middy gassed firearm. Do be aware that midlength gas systems in the .458S can cause functioning trouble. Some SBR and CorBon loads will not function reliably in a midlength gas nor will H110 loads many times. My CAR and handgun gassed rifles function flawlessly with H110 but the midlength gas will not run at all. H110 is too fast and the pressure curve is not correct for midlength gas, but switch over to the slightly slower Re #7 and the midlength runs like a bat out of hell, and Re #7 will also work just fine in the handgun and CAR length gas systems, although it does not give quite the velocity in the 12.5 and 16 inch rifles or 14 inch handguns as does H110. I'll definitely try out some Re7 when I get mine built. Marty said that my barrel would probably not like H110, but he recommended 4198 (not sure if he means H4198 or IMR4198, but I've seen a bunch of loads for each). Will the Re7 be a good choice for the 405 grn Remington pills in an 18" barrel? Thats all my local shop has right now in .458, but I'm likely to be waiting a month or so to get brass anyway. |
| I cannot answer first hand on that. I have not tried any 400 gr pills. The only ones I have loaded are 250, 300, 500, and 525. Sorry. H4198 or IMR 4198 both will work just fine. Just be sure to use the correct data because while very close and will function similarly, they are not the same powder. |
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