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Which process for hop up chamber removal on M4A1?

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#21 threadkill



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Posted 06 October 2008 - 04:49 PM

I finally got some time to try a few different combinations of bucking and nub, and to my surprise, the Firefly bucking and h-nub seemed to perform a little better than stock and H-nub. This was based on having fewer flyaways when shooting at long distances just to watch bb flight (calm wind conditions for most part). This was however during a short test; more to try, and getting the Firefly properly centered was the key, which is why I am writing.

During initial installations of the Firefly, I never could be sure that it was properly centered so the inside fins were directly under the nub. The chance of being offset is due to having to slightly rotate/twist the barrel and bucking while coaxing the bucking into the hop chamber. It is obvious that the bucking is deforming to some extent due to the fact that it has to be shortened in order to reinstall the c-clamp. That is, it starts out the same length as the stock bucking, so must be compressed and elongated to some degree. Stands to reason that it could also be stretching or twisting laterally, which would off-center the fins.

I was able to at least partially check for a centered bucking installation by installing the nub last. I did this by removing the gears from the hop chamber, which allowed the nub adjustment arm to hang down, exposing the hole in the side of the barrel. With the bucking and hop chamber fully installed on the barrel; c-clamp in place, I could look through the end of the chamber and barrel, and then insert a probe (about the size of the nub) through the space the nub arm normally sits. With the probe centered, and looking into the barrel with a light and magnification, I could push up on the probe to simulate the nub pressing into the bucking and see the fins pushing up into the barrel.

What's interesting is that on more than one occasion, the fins were not close to being centered. I'd then remove the bucking, re-lube, and then try a different combo of light twisting and pushing. After a few tries, I was able to center the fins; confirmed by the above test. I then installed the nub on the arm, attached the spring, pushed the nub arm up and into place, and then reinstalled the gears on the hop chamber. When I next get a chance to try a nub test, I'll switch nubs while leaving the barrel and bucking in place.

I'm sure you old hats have done this already, but I thought posting my experience might help another noob or new Firefly bucking user along. Being a bit of a geek and a tinkerer, this was also a great experiment and upgrade trial. I learn something new each time. This should also keep me occupied until my cylinder and M130 spring arrive, which I recently ordered... Never ends, huh?


PS - During some related searches, I encountered another long thread with the FireFly/H-nub argument, with a few stating that they preferred the combination. If I can find it again, will edit this post to include more data. Almost seems this entire subject needs it's own thread.

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