VELOCITY VERSUS BARREL LENGTH
Barrel length is not a stand-alone determiner of velocities and therefore energies. Factors such as barrel/cylinder gap, (in revolvers) chamber dimensions, chamber throats, (in revolvers) barrel throats, rifling depth and dimensions, rifling style or type, barrel material, bullet material and powder burn rate, etc., all have an impact on velocity achieved.
The above factors may far supersede the effects that barrel length alone has on velocity developed when firing any given load from any given firearm. Barrel length can only be meaningful in determining velocities if all else is always equal and the truth is “all else” is seldom, if ever equal.
As a few real world examples; I have two Marlin rifles chambered in 35 Remington. One has an 18 inch barrel and the other has a 22 inch barrel and yes the 18 inch barrel gives higher velocities with every type of ammo I’ve tested. I have two Marlin rifles chambered in 45 Colt. One has a 20 inch barrel and the other has a 24 inch barrel…………the 20 incher shoots faster with every type of ammo tested. Colt used to make the famed
Python model, chambered in 357 Remington Magnum, but every Python I ever tested, produced substantially slower velocities than most other makes and models of revolvers, with like barrel lengths! Why? Colt made the python with a choked barrel to enhance accuracy. What I mean by choked is that the bore of the barrel was tapered, starting at the rifled end of the forcing cone/throat and was .001 inch smaller at the muzzle. Yes this typically enhanced accuracy, but caused the Python to generate roughly 100 to 150 fps less velocity, with a 6 inch barrel, than most other makes of revolvers, if all (or most) else was equal……. This “Python” situation is a perfect example of how barrel internals can determine velocity to a greater degree than barrel length.
Often, customers want to know “what velocity” they will get with one of our loads out of their 24 inch wiz bang (insert any brand of rifle or handgun). I am not comfortable with giving meaningless answers to satisfy a customer, based on assumptions, as I truly desire to be helpful to our customers. Hence, this short article to explain the dynamics of how unknown barrel internals affect velocity generated from all barrels. This may also be a good time to read my article entitled “
HOW WILL THIS AMMO FEED AND FUNCTION IN MY GUN”.
In short, the only way to really know what velocity a given load will develop in a given firearm is to fire that load, from that firearm, through a chronograph that is properly working and properly set-up…….Oh yes, I have seen lot of improperly set-up chronographs, which results in folks getting misleading numbers.
Far too often, we humans are using generalizations in dealing with firearms. If we want exacting results, in any endeavor, we have to use exacting means. It takes time, knowledge and money to do things correctly in any pursuit. Exacting firearms usage is no different. If you want to know what velocities your firearm is generating with any given ammo badly enough, you’ll end up going to the expense of investing in a quality chronograph. I have three Oehler chronographs. I bought my first one in 1985. I’m certain the various Oehler models are not the only good chronograph on the market, but my results with Oehler have been very good, so I’ve never seen a reason to change. Hopefully this short article can be of some usefulness to our customers. Good shooting and God bless.
