(Update July 28th, 2015: I took the SCAR-L with above Guarder two-piece hop up and it functioned flawlessly in about two midcaps’ worth of testing on the field in both semi and full-auto. Consistency was solid and I was actually quite impressed with the range, although this could be attributed to the Maple Leaf 70 degree bucking and tightbore as well. Either way, it worked flawlessly, and seems so far to be an effective fix.)
Perhaps against my better judgement, I accepted a VFC SCAR-L in a trade. I absolutely love the SCAR platform for its handling and aesthetics, but completely abhor VFC’s SCAR for a single reason – the terrible, terrible, terrible hop unit design. It is made of poor quality plastic (leading to sheared hop adjustment wheels), it’s a bit too tight in diameter and thus only reliably accepts VFC hop rubbers, the hop up arm is shorter than standard and thus aftermarket hop nubs/rubbers aren’t nearly as effective in it, and worst of all, it is proprietary. Or so I thought.
Some internet sleuthing revealed that old-school two piece V2 M4 hop up units have been tried and tested in the VFC SCAR with good results. I’m kind of angry at myself for not thinking of it sooner – two piece hop units, like the VFC SCAR hop, are open ended at the bottom, allowing for the lower receiver to swing out during disassembly. Could it work? Could this be the answer to all my VFC SCAR-related problems, and make a solid, reliable platform out of a piece of junk?
The answer so far is: Yes. Read more after the break.
I ordered two hop units from Guarder and JG, as they were the only ones available on Ehobby where I was making the order along with some other miscellaneous airsoft bits and bobs. Ideally I’d like to get my hands on a Tokyo Marui one for some of that good ol’ TM magic, but figured the Guarder and JG ones would have to do for now. I ended up using the Guarder one as I have a little more faith in that brand than I do in JG. Note that the Guarder unit doesn’t come with hardware, so you’ll have to salvage one from a V2 unit (in my case, the JG one did come with hardware, so I took the stuff from that). Don’t use the VFC hardware, because as I mentioned earlier the hop arm is a little shorter than standard.
The next step is to shave down the “fins” on either side of the hop unit that keep the unit in place in the forward outer barrel block. Using the VFC unit as a guide, you’ll want to file/dremel the fins until they are roughly the same size, to allow the grub screws on either side of the outer barrel block to hold the unit in place. You want to be careful here, as if you shave too little the unit won’t spring back far enough to form a seal against the gearbox, as the stock hop unit does.
Above is the unit installed into the outer barrel block. Fits perfectly!
A chrono test yielded stable hop results of +/- 3 fps, which isn’t the most consistent range in the world but I suspect the other gearbox compression parts are causing the variance. I’m pretty happy with the results anyway, and I’m sure some fine tuning on the other internal parts will yield more consistency. Of note is the fact that I didn’t lose/gain any fps in comparison to the stock hop unit, meaning that the Guarder unit is working just as it should.
One thing to keep in mind: when reassembling the gun and mating the lower receiver to the upper, take care not to slam the lower back into the upper. As the Guarder unit doesn’t have the slanted fins that allow it to make way for the nozzle/gearbox, it may get jammed and damaged as a result. I use a small tool to push the hop forward as I push the lower receiver up and into the upper.
And that’s that – a fix for the VFC SCAR’s most glaring weakness. Now I can adjust the hop level and use aftermarket parts without fear of breaking the hop unit or incompatibility. The VFC SCAR platform is relevant again. Huzzah!
(funny story: I received this AEG in a trade from a teammate, who in turn received it from a former teammate, who I believe I might have sold the AEG to years back… meaning I purchased this AEG years ago and have now got it back. Guess it was meant to find its way back to me :P)