Geez, I spent about an hour looking for something to back up my bullsh--, I mean, statements based on what I thought was correct.
What I found was some good information on
snipercountry.com.
The link to the article:
www.riflebarrels.com/twistii.htm...and a quote from it to help get the idea across:
If a bullet is fired from a barrel that has no rifling, the force exerted on the nose of the bullet by the air will cause it to flip over and its trajectory will be wild.
To overcome this tendency, a bullet is spin-stabilized by rotating it about its long axis. The amount of spin required is determined by the specific gravity, shape and construction of the bullet, bullet velocity, and the density of the air it is going to travel through.
It is interesting to note that this force, or overturning moment, acting on the bullet nose is greatest when the bullet first exits the barrel. If a certain bullet-barrel combination will stabilize a bullet at the muzzle, the bullet will remain stable for the rest of its flight. Why is this so? As a bullet flies on toward the target and beyond, it is losing velocity rapidly as any trajectory table will show. For example a 68 grain bullet from a 6PPC leaving the barrel at 3150 fps will be going 2786 fps at 100 yards and 2449 fps at 200 yards (ballistic coefficient of .265 and standard metro conditions). The rotational speed of the bullet or its RPM's decreases at a much slower rate. The overall result is a lessening force acting on the bullet nose, and that force is being overcome by a proportionately greater spin rate compared to forward velocity. The down-range bullet therefore is more stable than it was at the muzzle. The only exception to this occurs when the bullet passes through the speed of sound. At that velocity, about 1180 fps, it may lose stability.I wouldn't spout off in an attempt to baffle anyone.
If I'm ignorant of facts and discover something to expose that, I'll admit my ignorance.
Better to do that, than remain a fool.
I hope this is good information for your bbl. length choice.
Look into the snipercountry.com forums for great info on bbl. length/rigidity (OK, you perverts, knock it off!); twist rates; muzzle BRAKES; etc.
Good stuff.
My Bushmaster V-MATCH A3 upper is the standard version, 24" bbl., which at present is the alternate upper for the original A2 Dissipator.
I would someday consider an A3 20" pre-ban upper just to have for the collection.
A new post-ban lower is on the list first, to be the other component in the V-MATCH equation.
Two rifles are more fun than one!