I think that the Gunner might look better with shorter exhaust pipes. I'm sure people will be looking into other options. I saw this Akrapovich exhaust set-up for the HD Street, and I thought it would be a good look for the Gunner.
You have to be careful fiddling with exhausts, especially on HD's and I think by extension victorys. The stock pipes are designed with internal crossovers to give you some semblance of a midrange. Why do you think so many big crusiers going BRAWP BRAWP BRAWWWPPPPPP, will scream like a banshee and accelerate like a baby. Straight pipes kill any midrange, they're grat for making power at the top of the band, which is proper fro racing applications but on the street you want it at the bottom and in the middle...
We said the primary tube size is important to these gas speeds. Keeping things simple, this is summed up as “the larger the tube, the lower the speeds”. For the expanding, hot gases a slower speed means a higher pressure and, conversely, a higher speed is a lower pressure.... BERNOULLI explained this mathematically for us a long, long, time ago.
Generally we want a lower pressure and a higher speed in the exhaust. Having a highly negative pressure in the exhaust during the overlap period when both inlet and exhaust valves are open, is the key to making power. Design will influence this but, in regards to the primary tube size, we can simplify things a bit.
The primary tube size will go up in relation to engine size. The size of the tube should be slightly larger that the exhaust port area which, in itself, will most likely be “D-shaped”. The “D-shape” flattens out the floor to the port to increase the flow on the “short” side or floor of the port. Having the tube size much larger than this “slightly larger” is no benefit whatsoever. Simply put, an increase of of 1/4” in diameter will shift the rpm band up about 600 rpm for the same size engine.