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KM4 SR7 FPS Upgrades


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#1 uriahskates

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Posted 29 March 2014 - 04:34 PM

Hello Forum Dwellers,

My SR7 is shooting around 280 FPS with .25s ever since I swapped out the barrel to a KM Head
6.02mm 395mm TBB where before it was 320 FPS with .25s with the stock barrel. I believe the reason
for this decrease is because the Piston Head O-Ring is most likely worn out by now. I will be opening
my gearbox soon and while I'm in there, I will swap the O-Ring and re-grease all the parts. Since it is
open, I want to upgrade the spring and cylinder. On hand right now I have a KWA M130 spring but I am
contemplating whether I should order the Type 0.5 Cylinder found in SR10s, SR12s, etc. My main goal
is around 400 FPS with .25s. Will the cylinder be necessary or will the M130 spring do the trick?

Thank you for your help.

Edited by uriahskates, 01 April 2014 - 12:46 AM.


#2 BLATEY

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Posted 29 March 2014 - 08:28 PM

From what I've heard you will need the 0.5 cylinder as you suggested with the m130.

#3 uriahskates

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Posted 30 March 2014 - 09:57 AM

View PostBLATEY, on 29 March 2014 - 08:28 PM, said:

From what I've heard you will need the 0.5 cylinder as you suggested with the m130.

Isn't the cylinder for compression with a longer barrel?

#4 BLATEY

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Posted 30 March 2014 - 10:25 AM

View Posturiahskates, on 30 March 2014 - 09:57 AM, said:



Isn't the cylinder for compression with a longer barrel?

Yes, that's what kwa uses in the sr10/12 series guns, but you can use it in your gun just fine.

#5 uriahskates

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Posted 30 March 2014 - 10:46 AM

View PostBLATEY, on 30 March 2014 - 10:25 AM, said:

Yes, that's what kwa uses in the sr10/12 series guns, but you can use it in your gun just fine.

What would the FPS average at with the cylinder and the spring? I read other forums regarding SR7
upgrades but they didn't give me the information I needed. I did find that people used the M130 with their
SR7's but they didn't say if they used the 0.5 cylinder or not. Will there be internal problems if I don't install
the cylinder? Do you think the M130 will reach my goal? 380-400 FPS is fine with me. Also, when I called
KWA, one of the techs said the M130 will get me to my mark. I called again to get another tech's opinion and
he said I needed the cylinder and the spring. So as of right now I am very confused on which path to take.

Edited by uriahskates, 01 April 2014 - 12:47 AM.


#6 BLATEY

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Posted 30 March 2014 - 03:57 PM

With the fps as low as your saying you will reach around 350 fps without the cylinder, but with the cylinder you should reach your desired fps. This shouldn't wear down your gearbox very much if you lube and shim. What is your field fps?

#7 Chicken

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Posted 30 March 2014 - 04:35 PM

I agree go with the cylinder your gearbox will be fine.

#8 uriahskates

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Posted 31 March 2014 - 07:50 PM

View PostBLATEY, on 30 March 2014 - 03:57 PM, said:

What is your field fps?

400 with .25s

#9 BLATEY

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Posted 31 March 2014 - 08:14 PM

View Posturiahskates, on 31 March 2014 - 07:50 PM, said:



400 with .25s

You can find these parts on kwa pro shop.

#10 uriahskates

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Posted 01 April 2014 - 12:17 AM

View PostBLATEY, on 31 March 2014 - 08:14 PM, said:

You can find these parts on kwa pro shop.

One more question BLATEY, I really appreciate your help by the way. Do I have to shim when putting in
these parts? I don't mind doing some shimming but I just wanted someone's opinion. Like a .1 shim under
the spur gear or something like that? I looked up some shimming jobs on YouTube and I was blown away by
the trigger response and just the unparalleled performance. Just wanted my gun something like that.

Edited by uriahskates, 01 April 2014 - 12:47 AM.


#11 BLATEY

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Posted 01 April 2014 - 05:05 AM

No, it's not a must unless your putting in a m150 or higher it is a good idea though.

#12 uriahskates

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Posted 03 April 2014 - 08:23 PM

UPDATE

I have opened up my gearbox and installed only an M130 Spring along with a new O-Ring and some cleaning and greasing. I put it back together and it shoots flawlessly, although the ROF did decrease with a 9.6. At the moment I do not own a chronograph so I did the poor mans' chronograph with a Coke Can. It shoots through the bottom of a Coke Can like a knife cuts through butter. As RWA states, a gun that can cleanly shoot through the bottom of a Coke Can is around 400 FPS. I will be going to a game this Sunday and I will use their chronograph and report the results with a .20 and .25 gram BB.

#13 gcw360

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Posted 05 April 2014 - 09:44 AM

View Posturiahskates, on 03 April 2014 - 08:23 PM, said:

UPDATE

I have opened up my gearbox and installed only an M130 Spring along with a new O-Ring and some cleaning and greasing. I put it back together and it shoots flawlessly, although the ROF did decrease with a 9.6. At the moment I do not own a chronograph so I did the poor mans' chronograph with a Coke Can. It shoots through the bottom of a Coke Can like a knife cuts through butter. As RWA states, a gun that can cleanly shoot through the bottom of a Coke Can is around 400 FPS. I will be going to a game this Sunday and I will use their chronograph and report the results with a .20 and .25 gram BB.
I'll be you are over 450 with .2's and could be as high as 480 (hop-up off).  Will me interesting to see the results.

#14 uriahskates

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Posted 21 April 2014 - 07:45 PM

View Postgcw360, on 05 April 2014 - 09:44 AM, said:

I'll be you are over 450 with .2's and could be as high as 480 (hop-up off).  Will me interesting to see the results.

Sorry for the crazy delay. Chronoed yesterday at 460 with .20's and 420 with .25's.

#15 gcw360

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Posted 22 April 2014 - 06:41 PM

Thanks.




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