Sorry I'll re-do my post for you mate since you won't take my word for it.
Maybe you didn't know but basically hop twist barrels are a magical science bullshit barrel. If you do it just right the gains are minor and in most cases probably a placebo.
However hop twist barrels are a really clever and interesting concept. They are designed to do two things:
The first is to allow air to flow around the bb as it moves through the barrel in a certain way to make the airflow transition from a laminar flow to turbulent flow whilst still inside the barrel.
The second is to cushion the bb from the sides of the barrel to give you a more accurate shot. The second point explains itself and is all people on the internet seem to grasp, but the first is not really understood as all of the source material is from obscure Japanese forums and is lost in the translation (if it was there in the first place).
The benefit of having a turbulent air flow is that is has less skin friction on an object than laminar flow. Establishing this inside the barrel, rather than two or three metres outside of the barrel has a large impact on the net energy loss of the bb as it travels through the air. Think about it, you're gun could chrono in at 330fet (100m) per second but it would not go 100metres in a second. Generally it would in fact only go 40-50 with the help of hopup. This is because all of this energy begins rapidly dissipating as soon as the bb begins to travel through the air. Air resistance is exponentially related to the speed of an object. This means that the energy loss is at its highest at distance zero from the barrel exit. So the sooner the bb gets in a turbulent flow the better, this results in less energy loss at the most critical location which translates to more range.
The problem with these setups is that they're "calibrated" for 0.2g bbs at around 300fps. Turbulent and laminar flows are based of the
Reynolds Number which has a key variable of VELOCITY not energy. So if you use 0.25s the speed is all wrong and it will basically function as a smoothbore but with a morderate fps loss due to the rifling (which are channels cut into the barrel rather than grooves protruding into the barrel). If you crank up the fps too high than the bbs will grind along ridges and go wild. Basically unless you use them just right, these barrels just give slightly sub-par performance or extremely bad performance.
But what if you get it right and all this bullshit im spouting actually does something?
Then you get a slight increase in range of about 5-10m which is quite nice when SEGs are only effective to 40m. But why bother with this on a pistol? Why bother using 0.2s to get kills at a range where these tiny 0.2s are just floating out of the air? People are likely to not even feel it (because you're using sub 300 fps and 0.2s after all). You can get the same gains from using heavier bbs with the normal setup which everybody does anyway (I can explain why this is the case too). Why bother having 0.2s for a pistol and 0.25s and above for SEGs?
If you're not in it for the science and doing it right than it's just not worth doing. So what I am trying to say is.....
Hop twists don't work off muzzle velocity.
Source : I have one.
(and a several university level qualifications in fluid dynamics)
Wed May 07, 2014 3:28 pm 
