Thread: 308 barrel length velocity loss

There is alot of variables when it comes to barrel length vs speed so theres no real once size fits all, you can estimate and theres some general rule of thumb "x fps for y inches of barrel" you can follow but alot of things can change the outcome like powder type used, and how hot the load is as that effects not just the peak pressure but the pressure curve as a whole.

Also worth noting that its not a linear thing, the shorter you go velocity exponentially drops. For instance a .308 shooting a 168ELDM in front of a stout load of 2206h, Will lose right around 50fps going from 24" to 22". However if you were at 18" and went to 16", you would lose around 80fps.

In respect of the OPs question, As some others have confirmed with real world results, Powder dependent if your doing 2680fps currently, you should land somewhere right around 2540fps.