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Magwell · April 19th, 2016, 00:16

Ok, fairly large update:

Fixing the Hop Up.... While the stock hop up seems to work ok, it's plagued with some unique design flaws:

1. O ring - the O Ring is needed to keep the hop up wheel from rotating, or falling off. Using an O Ring that's too small (Lets face it, they dry out and crack/break over time) will allow the hop up to back off to zero very easily. Regardless of the Hop Up, the O ring should prevent the wheel from free wheeling/spinning easily.
2. Nub, or... what is that? Normally (Ie basically every other hop up design) hop ups use an arm which has a half circle notched out to accept a cylindrical nub, placed horizontally. The M249 hop up rotates this nub 90 degrees so it sits vertically, like a barrel. This means you cannot use any kind of non cylindrical nub, and a portion (let's say something like 20%, just a W.A.G.) of the arm movement is lost due to compression of the nub. If retaining the existing hop up, cut the end off the ink reservoir from a pen and use that instead to maximize hop up adjustability & tuning.
3. Barrel retention clip. It's plastic and seems to like to move around/fall off easily in some cases. Keep an eye on it when the hop up is removed and make sure the barrel is locked in.

So what options do we have? The Bullgear (also sold under different names) hop up makes a hybrid of the typical hop up and the M249 hop up. This allows for a larger window opening for use with flat hop nubs, H nubs, etc. It also has a C clip which is secured with a locking screw, preventing the barrel from loosening at all, unlike the original plastic retention clip. This is the route I chose, combining a flat hop with a 6.03 Tight Bore barrel.

Parts:

1x Bullgear CNC Aluminum Hop Up
1x Firefly Namazu Flat Hop Nub with Roller Bar
1x Madbull 6.03 Tight bore Barrel (363mm length - this may be different depending on your M249 model)
1x Prometheus Purple Bucking

Procedure:

I used this video for reference: https://youtu.be/ZqXbVQshNpI

1. Disassemble the hop up, check the window opening, cut the Firefly nub to suit and install the roller bar.
2. Turn the bucking inside out, use a knife or dremel to remove all material protruding from the bucking (ie alignment channel and contact patch). Invert it again so the bucking is in its original shape.
3. Insert the bucking on the barrel, rotated 90 degrees so you have a clean contact patch. If you like doing any other mods, ie dental floss, do this now.
4. Insert the barrel and bucking into the hop up, spray lube or water may help if its tight.
5. reassemble the hop up, install the barrel retention clip, dial, and O ring. It's a great idea to head out to Canadian Tire (Or Home Depot, or wherever) and just grab an assortment of plumbing O rings. You can test fit various ones to find the ideal amount of friction on the dial.
7. Barrel modification. On my M249, I had to dremel a bunch of material off the inside of my outer barrel in order for the new hop up to move in/out freely. It would bind up and not allow the barrel to seal correctly with the gearbox otherwise. See the pictures below.

So, what kind of effect did the new hop up, barrel and Hop Up system have?

Chrono results:
5 FPS drop over the stock barrel/hop up/bucking combination when tested at 19 deg C indoors. When tested outdoors in +23 deg C, there was no FPS difference.

Range results: We measured a range out this time, setting targets every 25 ft... Conditions were: +23, slight wind (11km/h gust), sunny, 10% humidity.
250 Ft accurately, 260 Ft inaccurately (BB spread seemed to widen this last little bit... some dropped at about 255 ft, others continued), and able to lob inaccurately to 270 ft. At 270 ft it's a waste of ammo, at the maximum range, dropping BB's at a person's feet - acting out the Matrix would be super easy... A team mate was down range for the finite ranging indicating BB hit locations. A stationary human size target (in this case an actual human lol) is very easy to hit at 260 ft.

Trajectory: The BB trajectory is slightly different, rather than a more or less straight flight path with an arc at the end then dropping off... the BB travels more or less perfectly straight, hops very slightly, then drops rapidly.

All in all, I'm pretty happy with these results. Can't wait to game it!

April 19th, 2016, 00:16	#11
Magwell Trader rating Join Date: Sep 2012 Location: Edmonton, AB	Ok, fairly large update: Fixing the Hop Up.... While the stock hop up seems to work ok, it's plagued with some unique design flaws: 1. O ring - the O Ring is needed to keep the hop up wheel from rotating, or falling off. Using an O Ring that's too small (Lets face it, they dry out and crack/break over time) will allow the hop up to back off to zero very easily. Regardless of the Hop Up, the O ring should prevent the wheel from free wheeling/spinning easily. 2. Nub, or... what is that? Normally (Ie basically every other hop up design) hop ups use an arm which has a half circle notched out to accept a cylindrical nub, placed horizontally. The M249 hop up rotates this nub 90 degrees so it sits vertically, like a barrel. This means you cannot use any kind of non cylindrical nub, and a portion (let's say something like 20%, just a W.A.G.) of the arm movement is lost due to compression of the nub. If retaining the existing hop up, cut the end off the ink reservoir from a pen and use that instead to maximize hop up adjustability & tuning. 3. Barrel retention clip. It's plastic and seems to like to move around/fall off easily in some cases. Keep an eye on it when the hop up is removed and make sure the barrel is locked in. So what options do we have? The Bullgear (also sold under different names) hop up makes a hybrid of the typical hop up and the M249 hop up. This allows for a larger window opening for use with flat hop nubs, H nubs, etc. It also has a C clip which is secured with a locking screw, preventing the barrel from loosening at all, unlike the original plastic retention clip. This is the route I chose, combining a flat hop with a 6.03 Tight Bore barrel. Parts: 1x Bullgear CNC Aluminum Hop Up 1x Firefly Namazu Flat Hop Nub with Roller Bar 1x Madbull 6.03 Tight bore Barrel (363mm length - this may be different depending on your M249 model) 1x Prometheus Purple Bucking Procedure: I used this video for reference: https://youtu.be/ZqXbVQshNpI 1. Disassemble the hop up, check the window opening, cut the Firefly nub to suit and install the roller bar. 2. Turn the bucking inside out, use a knife or dremel to remove all material protruding from the bucking (ie alignment channel and contact patch). Invert it again so the bucking is in its original shape. 3. Insert the bucking on the barrel, rotated 90 degrees so you have a clean contact patch. If you like doing any other mods, ie dental floss, do this now. 4. Insert the barrel and bucking into the hop up, spray lube or water may help if its tight. 5. reassemble the hop up, install the barrel retention clip, dial, and O ring. It's a great idea to head out to Canadian Tire (Or Home Depot, or wherever) and just grab an assortment of plumbing O rings. You can test fit various ones to find the ideal amount of friction on the dial. 7. Barrel modification. On my M249, I had to dremel a bunch of material off the inside of my outer barrel in order for the new hop up to move in/out freely. It would bind up and not allow the barrel to seal correctly with the gearbox otherwise. See the pictures below. So, what kind of effect did the new hop up, barrel and Hop Up system have? Chrono results: 5 FPS drop over the stock barrel/hop up/bucking combination when tested at 19 deg C indoors. When tested outdoors in +23 deg C, there was no FPS difference. Range results: We measured a range out this time, setting targets every 25 ft... Conditions were: +23, slight wind (11km/h gust), sunny, 10% humidity. 250 Ft accurately, 260 Ft inaccurately (BB spread seemed to widen this last little bit... some dropped at about 255 ft, others continued), and able to lob inaccurately to 270 ft. At 270 ft it's a waste of ammo, at the maximum range, dropping BB's at a person's feet - acting out the Matrix would be super easy... A team mate was down range for the finite ranging indicating BB hit locations. A stationary human size target (in this case an actual human lol) is very easy to hit at 260 ft. Trajectory: The BB trajectory is slightly different, rather than a more or less straight flight path with an arc at the end then dropping off... the BB travels more or less perfectly straight, hops very slightly, then drops rapidly. All in all, I'm pretty happy with these results. Can't wait to game it! __________________ Last edited by Magwell; April 22nd, 2018 at 15:10..