Sunday, 26 June 2016

Mod: Flywheel Brass Guide (19/32" in an RS)

Something I've always hated about flywheels is the apparent lack of accuracy. Whether because I'm bad at setting up flywheel blasters or they just hate me, who knows. One of the steps I took towards trying to improve accuracy was switching to Worker flywheels, which as I noted in my review, work quite well. I decided to try a brass dart guide, as it was something I had the materials for on hand, and something that has had a lot of varying results.

I decided to use 19/32" brass as some of the tests I've come across involving 9/16" appear to affect muzzle velocity noticeably, and I wanted no muzzle velocity loss. I felt that 19/32" brass would be wide enough to not significantly impact muzzle velocity, but still narrow enough to improve dart flight paths.
I used a piece of brass 10.7cm long. I don't know how different a little longer or shorter would be, but I don't have the spare brass to find out. These measurements are based off the following "barrel" segment measurement, and the geometry of the flywheel cage.
The "barrel" section is just shorter than a dart, measured so that the dart tip would be exiting the "barrel" when the tail end is just leaving the flywheels. This measurement was based off what Hawki007 recommended on Reddit, and to me it makes sense. Any shorter and the dart tip is still free to flail about before the dart has finished accelerating, any longer and the dart will start dragging along the brass after leaving the flywheels.
The back halfpipe cutout I made to be 1.8cm. It could be a little longer, but I didn't want it interfering with mags at all.
The distance from the back of the pipe to the back edge of the flywheel cage is 2.1cm.
These are the horrendously awful cutouts I made for the flywheels. I was in a bit of a rush and had no idea how to make super clean, super nice circular cutouts, so I went for rectangle. The edges are all grinded down smooth and the flywheels fit in just fine, I just wish I knew how to make not-awful looking cuts for these.
Test fitting the brass guide. As awful as the edges look, the flywheels don't touch them at all so hopefully they don't cause me too much trouble. I haven't had them cause any trouble yet, but I may look at re-doing the brass guide more cleanly.
Brass guide in place, with the epoxy curing. If the brass guide isn't perfectly aligned with the faux barrel, you're going to have problems.
One last quick alteration to the flywheel cage, these middle ridges have to go from both sides.
I just used pliers, not pretty but it gets the job done.
One last alteration I had to do was remove the entire lower section of the brass form the magwell end. From what I've seen, most other peoples' brass guides maintain the lower lip, though I've mostly seen them on Stryfes, which have a much lower effective/combat ROF than Rapidstrikes. I found that especially at high ROF, darts loved to collide with the lower wall of the brass, jamming up the entire system. Removing that section of the brass allows the darts to slide up the ramp as usual instead of straight jamming if alignment isn't perfect. Again, while the cuts are rather messy, all sides have been grinded down to be smooth.
Finally everything done and installed. Note that this is installed in my Bullpup RS, hence the weird carry handle segment and the mess inside the magwell.
With a clip (mag) loaded in. The top dart should be cupped nicely by the brass halfpipe. This protrusion of brass also helps stop darts from popping out the top of clips (mags), something I have experienced before with worn out darts. This prevents top loading, but given the games I play and my playstyle, this is not an issue to me.

I've fired hundreds if not thousands of darts through the brass guide, both Kooshes and FVJs. I've fired lots of my own Kooshes indoors at home for testing, and a lot of FVJs through several Melbourne Nerf events. Once I'd cleaned up all the cuts and in particular removed that bottom lip, darts fed perfectly fine through the brass. Throughout all the events it's been used in so far, I've had maybe 1 or 2 jams.
Comparing my Bullpup RS side-by-side with my RS rifle, also with Worker wheels, I saw two contrasting results. Since my Bullpup RS had Falcons in it at the time, and the RS rifle Blade 180/-3240s, I felt that they were fairly well matched for comparative purposes. Using FVJs, there was no significant difference. FVJs with Worker wheels already have very good grouping at less than half a metre spread at ~8m, and it is largely to them that I attribute the greatly improved effectiveness of my RS's in combat. Using Kooshes however, there was quite a significant difference. My RS rifle would have a fair number of Kooshes go off at fairly wide angles (spreading up to ~0.75m wide at ~8m range), while my Bullpup RS would keep all of the Kooshes in relatively tight groups, probably around 0.25m wide at the same range.
With stock flywheels in my Bullpup, I saw noticeable accuracy improvements over not having a brass guide. However it was probably only a little better than having just Worker flywheels, if not directly comparable. If it's a decision between a brass guide or Worker wheels, then definitely go for the Worker wheels first.
Through several chronograph tests at several different MLF events, I have seen no significant muzzle velocity difference between my Bullpup RS and any other overhauled RS with Worker wheels, without a brass guide. I believe that 19/32" is wide enough to not significantly slow down the dart after it has left the flywheels, compared to 9/16", which I have seen in several builds reduce muzzle velocity noticeably.

Is a brass guide worth doing? If done right and you want the absolute best performance possible then definitely. Accuracy is significantly improved, and the brass also helps stopping darts from popping out of the top of the mags. You may want to consider removing the lower lip, as especially at higher ROF it will cause issues with darts getting stuck, but with that removed, a well cut brass guide should cause no issues. Because of the raw amount of time and effort required to make and install a brass guide, I probably won't be doing another one, but I'm glad that I did one for my Bullpup.

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