04-28-2020, 04:07 PM
The 16 barrel is a 1:9 twist CMV carbine gas system from J&T Distributing. The 18 barrel is Stainless Steel 1:8 twist Grendel II Liberty barrel mid length gas system from Brownells. The 20 barrel is a Shilen 1:9 twist Stainless Steel DCM profile rifle length gas system purchased from Midway USA. The 24 barrel is an Alexander Arms CMV 1:9 twist with rifle length gas system.
The results for the 12 PSA and 12 Faxon 6.5 Grendel are from forum members who posted their chronograph results. The shorter 6.5 Grendel in shorter barrel lengths have gotten a lot more common in the last couple of years so I included the data. The results from 16, 18, 20 and 24 results were obtained using a MagnetoSpeed and five shot strings.
In my opinion a Hornady 123 grain SST with chronograph around 2475-2500 FPS from an 18 barrel. In cold weather the velocity will probably be closer to 2475 FPS. My results were from a 70-75 degree day so if the temperature is 90+ degrees the velocity will be around 2500 FPS IMHO.
The results for the 12 PSA and 12 Faxon 6.5 Grendel are from forum members who posted their chronograph results. The shorter 6.5 Grendel in shorter barrel lengths have gotten a lot more common in the last couple of years so I included the data. The results from 16, 18, 20 and 24 results were obtained using a MagnetoSpeed and five shot strings.
In my opinion a Hornady 123 grain SST with chronograph around 2475-2500 FPS from an 18 barrel. In cold weather the velocity will probably be closer to 2475 FPS. My results were from a 70-75 degree day so if the temperature is 90+ degrees the velocity will be around 2500 FPS IMHO.