The bottom line to be safe is to use the published numbers that are out there, especially those from Marty as the real world has shown that these are safe, in as much as broken bolts are concerned. Again in reality, these pressures signs, like flattened primers, case head expansion and brass markings are in and of themselves not good. In reality, when we reload, we try and use conventional brass indicators to help us decide whether we are over the line.
#.458 SOCOM SUBSONIC TWIST RATE SOFTWARE#
And what we have are numbers generated from Ballistic software that generates the theoretical pressure for most of the loads that are out there. Marty designed the round to be held at 35K PSI out of deference to the bolt. There is to date no pressure data that has been made available as far as I know. we had someone as us to use an old 22 twist microgroove blank he had. We offer any odd twist you want as long as we can find it. RRA offers ONLY 14 twist, because of its ability to be used with all loads If you will never shoot anything other than 300 gr JHP, we can make you a barrel with 22 twist.īut, the 14 twist is the "jack of all trades" giving good accuracy with the 300 gr loads, decent velocity with the 300 gr loads, good accuracy with the 500-600 gr loads and enough stability to allow short suppressed rigs. If, like Jack, you will never fire a round heavier than 450 gr, the 18 twist will allow you to load a little more powder before seeing pressure signs. That way, if you run a 9.3" upper, suppressed with 600+ gr loads, your suppressor will not becoming a topic of good-spirited heckling back at the FOB. The last line is in reference and in direct agreement with what Jack stated - if you wish to have the broadest flexibility, you need to go with 14 twist. ġ4 twist is the all around best twist to use for this caliber If you have fantasies of being some kind of hi speed lo drag operator and want to use 600gr sub sonic loads in a suppressed 458, then you need to go 1 in 14".ġ4 twist DOES NOT degrade accuracy with any other loads, as low as 86 gr. 1 in 18" rifling will allow you to load to higher velocities before encountering pressure signs than 1 in 14".
The cartridge lacks the capacity to give good hunting performance with bullets over about 400gr. I went with 1 in 18" and suggest the same for anyone who sees this as a hunting rifle. 458 SOCOM will ever get shot enough for this to matter much. Also faster twist rifling picks up jacket fouling faster and also wears faster. Read a bit about the evolution of the 6.8 SPC for some good discussion on this point. So for jacketed bullets 1 in 18" is probably optimum for up to about 450gr.įaster than optimum rifling is slightly less accurate, but rifling slower than the minimum required will cause the bullets to yaw and tumble in flight making any accuracy imposible.įaster than necessary rifling increases chamber pressure, so loads must be kept milder to avoid pressure problems.
Required spin rate for stability depends more on length to diameter ratio than weight and modern jacketed bullets are longer than a plain lead bullet of the same weight. Modern BPCR (black powder cartridge rifle) shooters have found that 1 in 18" is more optimum for finest accuracy with 500gr to 550gr lead bullets. Not optimum for finest accuracy, but reliably stable. It selected 500gr because it was the longest heaviest bullet that would still stabize reliably in a 1 in 22" twist. The government later decided that it wanted a longer heavier bullet for better long range performance. The original 45-70 had a 1 in 22" twist because that was found to be optimum for the 405 gr lead bullet that was originally standard. 458 Socom is more or less a rebated rim 45-70.
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