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Discussion Starter · #1 ·
I haven’t seen much talk about this but I’m sure someone on here has insight. Is it better to have a fixed arm with a solid nub or would it be better for a spring pressure arm ( like what comes out of the box ) with a fixed nub? I’m going for consistency and accuracy, not capability of weight hop. I imagine an arm locked down with a solid fixed nub would be best no?
 

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A two piece setup (arm + nub) is theoretically better because the nub can conform to the shape of the bucking regardless of the radial position of the arm. However, there is so little radial movement that I'm not sure this makes a huge difference. I'm a huge fan of Masada's arms, which compensate for this offset angle and result in a virtually flat pressure on the bucking. I like the one piece setup because it involves less moving parts, and theoretically more consistency.
 

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Discussion Starter · #4 ·
A two piece setup (arm + nub) is theoretically better because the nub can conform to the shape of the bucking regardless of the radial position of the arm. However, there is so little radial movement that I'm not sure this makes a huge difference. I'm a huge fan of Masada's arms, which compensate for this offset angle and result in a virtually flat pressure on the bucking. I like the one piece setup because it involves less moving parts, and theoretically more consistency.
I forgot to mention I’m machining a chamber and all the parts so there will be little to no play or rotation. I wasn’t sure if the spring had a benefit or not. I feel like the spring is just one more variable that can be avoided.
 

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If you are referring to the spring on the AA chamber, its only there to apply back pressure to the arm to push it against the adjuster. Other than that, it doesn't do anything. Any instability will stem from the nub itself and imperfect mating surfaces. Without the spring you are relying on the bucking to do that, which could be detrimental to your bucking's health and longevity.

I don't mean any offense by this, so don't take it that way. I think it's hilarious that people are hell bent on building a better rifle, custom making parts, then not understanding why the spring in the AA chamber is there. If you are going to improve something, then you need to really look at what each part does and its full functions and what it experiences during use. Then you need to answer, "Why was this designed this way?"
 

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In my opinion having a spring return nub/arm is better, but not always necessary. It should be more consistent for the spring to apply the back pressure to the arm/nub to hold it in place than relying on the hop up bucking to do it. However in a lot of the chambers it can be difficult to do with space constraints. I removed that feature from my arms because the 3D printed material couldn’t stand up to the spring that AA includes with their chamber. On the TDC I designed I sacrificed a lot of space to get a spring in there for the consistency.

I’ll also add that it also depends on how much the nub and arm combo weighs or any resistances it has in its movement. In theory a very lightweight arm and nub with no friction in its movement shouldn’t need a spring, but that’s definitely not always the case.
 

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The spring in a hop unit helps keep unnecessary pressure of the bucking which helps consistently as this means the spring is taking most of the pressure from the hop adjustment.

Also a problem with a fixed hop setting is
A) how do you get hop unit and barrel to fit together during assembly (assume you would need to use an open cut vsr barrel to avoid issues)
B) as bucking wears away you lose hop
C) ever change ammo weight or even brand and hop might be out

Lot of downside for making a fixed setting hop unit, years ago during the move to modern Airsoft guns didn't have hop > than they had a set hop (like Springer trishot shotguns still do) > than adjustable hop was invented.

Seems silly to go backwards for a problem that doesn't exist if any rifle is built right. (Aka shimmed hop arm)
 

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Discussion Starter · #11 ·
If you are referring to the spring on the AA chamber, its only there to apply back pressure to the arm to push it against the adjuster. Other than that, it doesn't do anything. Any instability will stem from the nub itself and imperfect mating surfaces. Without the spring you are relying on the bucking to do that, which could be detrimental to your bucking's health and longevity.

I don't mean any offense by this, so don't take it that way. I think it's hilarious that people are hell bent on building a better rifle, custom making parts, then not understanding why the spring in the AA chamber is there. If you are going to improve something, then you need to really look at what each part does and its full functions and what it experiences during use. Then you need to answer, "Why was this designed this way?"
I’m not specifically talking about the AA chamber, more or less in general there is usually a spring. And none taken. I’m trying to understand everything so when I do try things I’m not chasing my tail. How do you think all these people/companies got to make these products that work? They tried different things.
 

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I’m not specifically talking about the AA chamber, more or less in general there is usually a spring. And none taken. I’m trying to understand everything so when I do try things I’m not chasing my tail. How do you think all these people/companies got to make these products that work? They tried different things.
I wouldn't go by the theory that a company tested it so it must work, we've all tried a product clearly not designed well or fit for purpose that a simple real world test would have discovered.

Sometimes the answer of why is it designed that way is best to think about what the part is doing and how it's working.

Best example is engines they haven't drastically changed in decades of their basic design just refinements and clever electronics being added.

I see it as Airsoft has reached this point as an analogy we've got the core concept right now it's just refining the designs.

In your design of a "fixed arm" do you mean fixed hop setting or one piece arm?

I would include a spring with any adjustable hop unit as it should allow a better consistently of hop setting. Takes pressure of hop rubber of supporting arm weight.
 

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Discussion Starter · #13 ·
I wouldn't go by the theory that a company tested it so it must work, we've all tried a product clearly not designed well or fit for purpose that a simple real world test would have discovered.

Sometimes the answer of why is it designed that way is best to think about what the part is doing and how it's working.

Best example is engines they haven't drastically changed in decades of their basic design just refinements and clever electronics being added.

I see it as Airsoft has reached this point as an analogy we've got the core concept right now it's just refining the designs.

In your design of a "fixed arm" do you mean fixed hop setting or one piece arm?

I would include a spring with any adjustable hop unit as it should allow a better consistently of hop setting. Takes pressure of hop rubber of supporting arm weight.
Fixed as in adjusted to the proper setting then either locked down or make the adjustment mechanism super rigid. Arm/nub one piece.
 
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