What to look for in a hop-up unit?

[Immelmann]

Hey guys, I was hoping someone could help me get an idea of what to look for in a hop-up unit. I'm looking at buying an AGM MP44, and while everyone seems to praise its sturdiness and metal gearbox, it seems to be universally agreed that it's inaccurate as crap. From what I understand most of its issues are related to a cheap hop-up that requires readjustment every few shots (if it even does anything), but the good news is that it's just a standard M4 unit.


Three of my uneducated considerations include:
Tokyo Marui

Modify

Madbull

My only concern with the Madbull is that I can't tell whether I'll be able to adjust it once installed. It appears to have the adjuster knob on the rear, so I don't know :S
Here are two pics I found of the stock unit:




Any help would be greatly appreciated!

[Amos]

The modify one is fine.

[Forever_kaos]

I have the modify unit in mine, works great!

[Stealth]

A "bad" hop-up unit could be mis-diagnosed. A few things should be considered before beginning to swap hop units:
1) Is your hop rubber making a good seal with the nozzle?
2) Is your hop unit moved as far back towards the mechbox as possible?
3) Are there any air leaks between the inner diameter of the hop unit and the hop rubber and barrel?
4) Is your inner barrel "locked down"? (ie: any movement of the inner barrel when the gun is fully assembled?) You should be using barrel stabilizer rings. I personally use some custom barrel lock-down bits from HS5.

After you've checked all of those, then you can start taking a look at the unit itself.
1) The hop unit should fit against the mechbox and outer barrel with minimal play or wobble. Axial movement of the hop unit will cause inconsistencies
2) The adjustment wheel should be tight, if it's basically free-spinning, that is what causes the hop adjustment to unwind itself.

The Marui one wouldn't even work on your gun, unless you are currently running a 2-piece hop up a la Marui old-school plastic M4 body.

The Madbull unit can be adjusted once installed. I have one, it leaks..somewhere. I don't use it.

ALL things being equal, Modify hop units consistently give me 30fps less than a G&P, Systema and Lonex unit. It's actually a very consistent unit and looks/feels quite nice, but the fps loss is puzzling and somewhat alarming. I do like the solid nub that it comes with though. I've since moved away from the Modify unit.

Last week I was at Ultimate Airsoft and for whatever reason my SBR that had a Modify hop unit decided to stop feeding correctly. I thought it was the ammo (bastard .2g), but tested it with my regular Madbull .28 and it had the same problem. Swapped over to a G&P hop unit, worked fine the rest of the night. IMPOSSIBRU???


More info/testing/comments here:
http://www.airsoftcanada.com/showpos...7&postcount=16

[Immelmann]

Not having one myself means I can't diagnose anything yet, but by the sound of it it's just a generally crappy unit.

By consistent do you mean accuracy or velocity? And is the FPS loss worrisome enough to warrant looking at other brands, eg. G&P? Or should I just go for the Modify?

[Rusty Lugnuts]

i spent a bunch of time looking into hop ups a couple months ago, i remember i had decided on the G&P metal hop up. it's about $ 25 bucks at a retailer in toronto.

[Stealth]

Originally Posted by Immelmann

Not having one myself means I can't diagnose anything yet, but by the spun of it it's just a generally crappy unit.

By consistent do you mean accuracy or velocity? And is the FPS loss worrisome enough to warrant looking at other brands, eg. G&P? Or should I just go for the Modify?

Inconsistent FPS = decrease in accuracy.
Loss of FPS, put it this way, if you put an M120 spring, you're expecting ~400fps. If you get only 370fps, how would you feel? If you don't mind, then go for the Modify.
I would go ahead and say your mileage may vary but I DID test with 2 Modify units and a boxful of other units...

[Immelmann]

Apparently this shoots hot enough that the loss might not be a problem, but I'll see what happens. The local field limit is 400fps, so if anything that should be a good thing. I'll still probably have to look into springs though.

[MaciekA]

Originally Posted by Stealth

ALL things being equal, Modify hop units consistently give me 30fps less than a G&P, Systema and Lonex unit. It's actually a very consistent unit and looks/feels quite nice, but the fps loss is puzzling and somewhat alarming. I do like the solid nub that it comes with though. I've since moved away from the Modify unit.

We need access to some high resolution 3D scanners so that we can figure out what differences in internal design are causing these issues, in detail. Either that or some kind of X-Ray photography when the gun is assembled and nozzle is fully forward. I'd love to know what "reference" gearboxes, buckings, and receivers are being used by Modify / Lonex / etc to determine the optimum dimensions and shapes for their units.

[nstahl.19]

My G&P hop up that came stock in the G&P AEG had all kind of problems. Didn't matter how hard you tightened the screw, the hop up wheels would always slip, unless I jammed it at the max hop, where it would stick. I took it apart cleaned it, deburred it, didn't do much. So basically whenever I tried to set it, the spring would force it back down. When I did have it set, with out it moving, after a single shot it would slip. Could just be the hop up gear/wheel set, they didn't seem to align properly. I'm yet to try a new one.

[Stealth]

Originally Posted by MaciekA

We need access to some high resolution 3D scanners so that we can figure out what differences in internal design are causing these issues, in detail. Either that or some kind of X-Ray photography when the gun is assembled and nozzle is fully forward. I'd love to know what "reference" gearboxes, buckings, and receivers are being used by Modify / Lonex / etc to determine the optimum dimensions and shapes for their units.

Honestly in my mind the ONLY reference that should be used is Marui which - fortunately - Systema has seemed to duplicate quite well.

[Stealth]

Originally Posted by nstahl.19

My G&P hop up that came stock in the G&P AEG had all kind of problems. Didn't matter how hard you tightened the screw, the hop up wheels would always slip, unless I jammed it at the max hop, where it would stick. I took it apart cleaned it, deburred it, didn't do much. So basically whenever I tried to set it, the spring would force it back down. When I did have it set, with out it moving, after a single shot it would slip. Could just be the hop up gear/wheel set, they didn't seem to align properly. I'm yet to try a new one.

Yeah G&P hop units tend to do that, there's an easy fix for it - just sand down the post where the adjustment wheel sits such that when the screw is installed the pressure isn't on the post but the wheel itself. Then the wheel won't slip. Alternatively a small lock washer works.

[nstahl.19]

Originally Posted by Stealth

Yeah G&P hop units tend to do that, there's an easy fix for it - just sand down the post where the adjustment wheel sits such that when the screw is installed the pressure isn't on the post but the wheel itself. Then the wheel won't slip. Alternatively a small lock washer works.

Thanks, that was going to be my next try.