How effective are Concave Hopup Spacers/Nubs?

[Air JezAss]

I've heard a bit about these concave spacers lately, and would like to hear what people have to say about them who have already installed them in their guns. Do they really reduce the lateral movement of your BB's, or is the change in performance barely noticeable? What is your preferred bucking with a concave spacer? Here is a link to the PolarStar version www.airsoftpost.com/product_info.php?products_id=31599, for members who haven't heard of these.

[TheEnd]

When installed correctly they are amazing.

I have been using the SCS/PCS nubs exclusively for quite a while. Correct instillation requires several things.

- Removing the "nub" from the bucking. If you turn the bucking inside out you will see a small internal nub. That mound of rubber will prevent the SCS/PCS from working 100% because the rubber fills most of the concave. I flip the bucking inside out and use a file and sanding sticks to remove the mound. The problem here is that doing this drastically reduces bucking life.

I have tried using the SCS/PCS with an unmodified bucking, one with the nub half way removed, and one with 1/4 of the nub left. The more of the mound you remove the better the SCS/PCS works, but the more you remove the shorter the bucking lasts. It is up to you to decide what balance works best for you. It does help when using an unmodified bucking, but the results are nothing like a completely removed one.

Also, that mound of rubber will cause vertical deviations. Because the SCS/PCS is a hard nub the only thing the bb will compress is the rubber between it and the SCS/PCS. If you use a bucking with a full mound the rubber will compress differently every time. This will cause slightly different amounts of hop each time. With the mound fully removed there is less rubber that can deform, which means that the shots will be more consistant.

In short the more rubber you remove from the mound the better the SCS/PCS will work. The trade off is bucking life.

- The SCS/PCS should be glued to the hop up adjustment arm. Because of the concave shape the SCS/PCS tends to cause shots to hook left or right, and sometimes both. This is because the hop up arm is flat part trying to hold a concave part. A normal bucking is flat and is held captive by the flat hop up arm. The SCS/PCS will sometimes cant itself and cause a hook.

When gluing the SCS/PCS to the arm I always use a jig and epoxy. Use something that can withstand impacts. Superglue is brittle and will most likely break after a while.

- Shim the hop up arm. Once the SCS/PCS is glued to the hop up arm it should be shimmed inside the hop up chamber using metal tape or shims. Again this is because the SCS/PCS is hard and will not deform like a normal nub. Because of this it must be held as straight as forward or else it will cause a hook or potentially even a jam.

Those steps will allow the SCS/PCS to work 100%. If you simply drop an SCS/PCS in an unmodified hop up system the results may or may not be worth it.

[triggs]

A "H-nub" or concave nub also will wear out the bucking more quickly than a traditional nub. Due to the way the concave nub grips the BB, and the material required to be removed, after enough use, the bucking itself wears down. This leads to consistent, wild, and inaccurate shots.

When they work they are amazing, but if you tend to lay on the full auto a lot, expect to be changing buckings frequently. Buckings are cheap, but the question becomes, is it worth setting the concave nub up, and replacing the bucking?

[Air JezAss]

Thanks for the advice guys. So if I removed the mound and the bucking wore down, would it work if i removed the guiding strip from the inside of the bucking and rotated it to wear on another portion of the bucking, or would this reduce performance in some way?

[TheEnd]

That would work as long as the bucking doesn't have a hole worn into it and isn't torn. It could be difficult if the bucking fits tightly into the hop up because the entire guide strip would have to be completely removed.

When my buckings fail from removing the mound they always tear. When I pull the trigger it makes a choked off sound, the bb roles out of the barrel, and the next shot is an expected jam. If you did catch it before it broke you could rotate it, but it will most likely just tear.

EDIT: Reading over my posts it makes it sound like the SCS/PCS is more trouble than it's worth. I want to drive home the point that doing the above things is to make it work 100%. I would highly recommend picking one up and trying it out while keeping everything else stock. If the SCS/PCS is only at 40% or whatever it might just be better than your stock nub. Only way to find out is to try. They are only $5 or so anyway.

[triggs]

Removing the guide strip won't work as it creates a large channel for air to escape by. Even lashing the bucking will not solve this particular hole.

Buckings are cheap, if you really bother with a high performance concave nub, why bother trying to save $5 by attempting to reuse the bucking.

[TheEnd]

The cut in the barrel could be filled with silicone glue. I have used it to fix ripped buckings with large holes or tears in them. It holds up amazingly well and will actually bond to the barrel and bucking to the point that they are difficult to seperate.

As stated, buckings are $5. Just replace it. Less things to go wrong.

[Air JezAss]

yeah, it sounds like it might be more trouble than what it's worth to cheap out on buying a new bucking. I'm glad I have a spare right now so when it tears or wears down to much, I'll be prepared.

[Tex]

Where can you get a good, quality bucking for $5.00? I'm having a hard time finding that good of a deal, usually $10.00 or more for a good one. I'm just asking because I'd totally jump at a few extra for $5.00 a pop if they aren't some Matrix or other cheap Chinese brand.

I would also like to mention something that TheEnd did not mention. If you are using an SCS/PCS nub and you completely remove the mound of rubber from the inside of your bucking, there is quite a good chance that you will not have enough of a hop up effect anymore. I had this happen with my first go around at this. What I did to fix this was place a little extra super glue underneath the SCS nub when I glued it onto the hop arm, this caused the spacer to push further down into the chamber and actually create an effective amount of hop up. You just have to insure that the SCS nub sits flat otherwise it will veer off to the side. Another option would be to glue a small piece of flat plastic under the nub and on the hop arm, to maintain a level surface to glue your nub to.

So before you just glue your SCS nub into your hop up arm, do a test run without glue to confirm whether or not it will still effectively hop up without the mound of rubber. This is really dependent on the hop up unit you are working with. My experience was with my G&G M14.

[TheEnd]

I have personally never run into the problem with not enough hop after removing the mound. Now that I know it can occur I would do as Tex said and check it before you glue it.

As for the $5 bucking it looks like the Systema has gone up in price. I remember buying them from airsoft Atlanta for $5 back when I started playing. Now Airsoft GI has them for $6.75. Close enough I suppose. I have tried just about every bucking on the market in the quest to find the best. Time and time again the Systema has proven to me to be the best in terms of accuracy, range, life, and cost.

I have had good results with Guarder, Prometheus and fire fly also. The problem is that in my experience these more expensive buckings have not outperformed the Systema by a large enough amount to make them worth 2x the cost.

[Air JezAss]

on average, how long have your buckings lasted after being sanded down?

[ctres]

I know that the guarder clear bucking can be had on ehobbyasia and wgcshop for about $3.00, but shipping might not be worth it for just one. Lots of people seem to really like this bucking, but I have also heard a few negative reviews, but I can't remember what the complaints were.

Some people also seem to like to sand down the bucking but still use a flat nub, simply because it is easier to install consistantly and involves less fiddling and fine tuning than the scs sometimes does. I really don't know which is actually better in terms of performance, but some people say that the flat nub is just as good. I believe that it would also extend the life of the bucking.

Regarding the small groove, I have heard that filling it with clay also works, and it is quite easily removable.