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Hopup Installation?

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#1 Hibiki



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Posted 14 February 2014 - 12:39 PM

Hi everyone,

I ordered a new hop-up for my KWA MP7 since my original one had swollen and was causing feeding issues. However, after installing the new hop-up, I find that, though my feeding issue is fixed, the hop-up is imparting an angled spin on the bb, causing it to curve left.

The hop-up I ordered is this one -> http://www.evike.com/products/44335/ (the Angel Custom V-type Hopup Bucking for KSC SMGs)

As far as I can tell, I believe that I installed the hopup correctly, but I'm unsure if this hop up is actually designed to work with the MP7. As far as installation goes, how precisely does the hopup and barrel need to be aligned? The barrel is as straight as I could get it (though, I find that there is a little play in it, even despite the flat part made to help align it), as is the hop-up. When I look down into the "plunger" hole, I see the indention on the hop-up nub directly in the center.

However, the Angel Custom Bucking seems to be different from the stock hopup rubber in a number of ways:

1) It's slightly longer on one side.
2) the little flat cutout on the outside (which goes to the rear I presume?) is on the top, rather than the bottom (where it is on the stock KWA bucking)
3) It comes with a small ball bearing, without which it didn't work properly at all. As far as I can tell, the KWA bucking does not use a ball bearing, correct?

A fourth concern, which might be attributed to the problem, is that when I recieved my bucking, it was packaged in a tiny ziplock back which squeezed it into a slightly oval shape on one side. I'd imagine that stretching it around the barrel as it is on installation should make this a non-issue, but I thought it would be worth mentioning.

So, given all of that information, is there anything that I'm doing wrong, or is the hop-up bucking merely unsuited for the gun? I'd like to replace the KWA bucking so as to alleviate any future swelling issues.

I've ordered an A+ Reaps bucking made specifically for the KWA MP7, so I will try that when it comes in. However, I'd still like confirmation on how to install it (ie, which side goes forward / to the rear, whether I need a ball bearing or not, and how I can know that my barrel is correctly aligned). I've watched the pinned video this, but it doesn't address any of these questions.

I'm also curious to hear from anyone who has tried the bucking I have now, and if it worked for them or not.

Thanks in advance!

#2 905taylor905



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Posted 22 May 2014 - 08:04 PM

I purchased the same bucking, and have had the exact same problem.
All of my shots tend to curve left very sharp around the 75 foot mark.
I have cleaned, oiled and reset the bucking numerous times with no luck.

I did stumble upon one thing I believe causing this problem in my case, and that is the bucking itself or the mp7 hop up window.  (I have only purchased one replacement bucking and am not sure if all buckings will have the same alignment issue)  
With the angel custom v type bucking, if you look where the plunger would apply hop up, after installing the bucking and barrel back to the gun, you will see the small hole in the bucking and the hop window do not line up properly.  So when the plunger is in to apply hop up, it is actually pushing down on a piece of the bucking in which is ment to hold the bb in place prior to being shot.

I noticed this after looking down the barrel and applying hop up to notice I wasn't seeing the "v" teeth, but the whole bucking was actually bending down and bbs would not have been able to fit.
So I opened it to find the alignment issue.

I have not tested this yet, but I shaved down the front of the bucking until the hole matched the mp7 plunger hole perfectly...
I will post my results once tested, but chrono was 400 fps solid. (Chrono but no distance to test flight)

I will say that it seems the bucking was a little squished right from the beginning, and shaving it almost made the fit much more snug, rather than tight and a little deforming.

If this did not fix my issue I have heard some good things about the reaps bucking working wonders, and even increasing accurate range by 25-50 ft.

Hope this helps.

#3 905taylor905



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Posted 26 May 2014 - 06:16 PM

I tested this and it was no better. I re-installed everything and teflone taped the bucking in place where I was happy with it and it worked well about 500 rounds.    Very accurate I might add to around 120ft. Which isn't bad at all for such a short barrel.    But it wiggled its way out of place and started shooting left again.

I am not sure if the molding was bad on the bucking or theres something I'm doing wrong.  But it's been reset about 10 times now and I'm sure it's the bucking.  

I need to force it and kinda off set it to make the teeth line up even, And once I slide it back into the chamber, it's off.  But when I do get it set only a few bbs through it before its shooting left.   Of course the Teflon tape held it tighter a little longer but that's no fix I'm looking for.    

I'm looking into this.   May be something to look into.

Edited by 905taylor905, 16 June 2014 - 07:36 PM.

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