Does a ported barrel have a slower muzzle velocity than a non ported barrel? (both using the same type shell) If so how much slower??
I know that I have covered this a few times before, but it never hurts to drive another stake into the heart of the “porting” monster. Besides, I may have changed my opinion.
Modern smokeless powders almost always get their burning done within the first two feet of the barrel or less. This means that by the time the shot load hits the porting area, it is going just about as fast as it ever will. Porting has little effect.
However, porting does have some effect. It is easy to show that shotgun loads lose velocity in shorter barrels. If you compare a 26″ barrel to a 30″ barrel with the same load, you will note a very slight fall off in velocity (just as you can show a fall off in velocity if the barrel is too long- it’s due to friction). If velocity can fall of a bit due to four inches less barrel, then some small part of it “ought” to happen with porting. The problem is that the difference is so small that it is difficult to measure against the normal shell to shell variation. We are talking really small numbers here of a few feet per second. This has nothing to do with what happens with pistols or rifles. We are talking shotguns here and that is another ball of ballistic wax entirely.
So, with the right equipment and specially selected slow burning powder, I am sure that you could show a slight loss of velocity to porting, just as you can show a very slight reduction in muzzle jump on a ported shotgun. In neither case is it big enough to matter. However, the muzzle blast from porting may well matter.
Shotgun Report’s Technoid
(Often in error, never in doubt.)