How to access VFC SR25 hopup

[stryker20000]

So, after tinkering and taking it apart messing with the hopup and barrel, I finally got good pics a few weeks back to do a guide that I hope helps other people in gaining access to their hopup.  At the end ill toss in a few tidbits that I find work with it.  Also this is my first time attempting to post something like this on the forum with pictures so I do apologize if they are too big.  If they are I will try my hardest to resize them.  So, here we go.

 

First I would highly recommend separating the upper receiver from the lower receiver, removing any optics you may have on it and take the front sight post off.  This will aid in maneuvering the rifle around with what you have to do. 

 

1. First step is to remove the front outer barrel.  This piece unscrews counter clock wise.  Take note of the rubber o-ring at the end of the barrel for stabilization.  Remove that as it will get in the way. 

 

2.  Second step is to remove the pins from the front rail system.  Now, they do only go out one way so you will have to look at the pins for which direction they go out from.

 

3.  There is an allen screw under the front rail guide.  Loosen or remove this screw. 

 

4.  What you will need to do is turn the gas tube/ hopup adjuster to the right in order to loosen the front rail segment.

It should start to come out and you might need to tug it a bit here and there to get it out.  End result should be something like this:

 

5.  Once you remove the front rail segment/ gas block you will need to start taking apart the rail as you would any normal free float rails.  I wont go into great detail on removal but its simple.  Just start unscrewing the screw thing (pulling a blank on the name) as shown in the picture.

 

6.  Separate the rail segment from the receiver and you will see an allen screw with three pins.  The three pins are removable, but take note on placement to assemble the rail again.  This will also be a good time to remove the hopup adjuster.  It should just simply pull out.  Remove the allen screw in the picture. 

 

7.  You will need to remove the ring with the holes in it (again I am pulling a brain fart on its name).  The tool I am using is an AR tool that came with my WE M16 gas rifle and works well to remove this.

 

8.  End result is you now have access to the hopup.

 

Simple to take it down.  Remove the two allen screws on the large cylinder and pull it off towards the end of the barrel.  There is one more screw that holds the two halves together that can be taken out to gain access to the bucking.

 

Please note this piece on the hopup unit when putting the rifle back together.

That silver looking tab on the hopup needs to line up with the upper receiver's top for proper placement.

[stryker20000]

I still cannot figure out how to delete posts so I will use this to add in small stuff I found interesting on my rifle.  I can use WE GBBR VSR buckings on it with the stock barrel and so far it looks like I can use standard WE GBB barrels.  I had another spare inner barrel laying around that I did not know of (M4 length) and test fired it in my back yard.  I still need to do long range testing but I was able to get it to feed no problem on an old REAPS + bucking.  I will come back in the future when the weather warms up here and I have a better WE barrel installed which should be here tomorrow.  I am also going to try and modify a Maple Leaf nub to better fit onto the hop arm as I currently have flyers shooting to the left and right using .36's.  Only problem is I cant fully determine how many are going left and right since they are black bb's.  In another post another person (3vi1-D4n) stated that the arm is the culprit for the flyers.  With the stock bucking I did find that I had flyers going up and to the right every 5th or 6th shot, but replacing the bucking did reduce that amount to 1 every 8th shot about and wasnt as bad.  I am just hoping my little mod with the nub helps.  Testing with the WE barrel,  stock and REAPS + bucking was done using .25 bb's. 

 

There may also be an easier way to take the rifle apart with the outer barrel.  Step 7 picture has two allen screws on it on both sides of the barrel.  You should be able to remove those and just unscrew the whole front outer barrel.  I cant on mine as I stripped the threading too much on my first attempt on take down.  My bad.

 

And two more pics of just because. 

 

[stryker20000]

Wanted to add to this.  The stock inner barrel is 495mm in length.  Also if you add a larger barrel to the rifle you can unscrew the fake barrel rifling with a large enough flat object, like a butter knife.