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sheywood

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Reply with quote  #1 

ISSUE / QUESTION

I swapped out the stock Krytac Kriss Vector AEG (US Version) 155 mm barrel for a Prometheus 6.05 "BC Bright" Brass Tight Bore Inner Barrel for Airsoft AEG (Length: 247mm) and using my non-scientific qualitative testing methodology saw a significant drop in FPS. I've eliminated user error during installation. Based on what I've read I was expecting a slight to large increase in FPS. 

Note: I re-used the original bucking on the new barrel, I did not get new bucking. I'm using a Valken Airsoft Battery LiPo 11.1v 1000mAh Battery and I've replaced the stock spring with the Evike.com Irregular Pitch Airsoft AEG Tune-up Spring (Power: M125 400~470 FPS)

Any thoughts on why I didn't get the speed up others have spoken about?

 

QUALITATIVE TESTING METHODOLOGY

There is a tree in my back yard about 85 feet from my patio doors. With the stock barrel a .28g BB gets to the tree on a flat line in a "one count"

With the 247 mm barrel a .28g BB barely reaches the tree after clearly dropping a few feet and takes a little more than a "two count"

ELIMINATING USER ERROR

  1. When I installed the 247 mm barrel I used a new barrel clip
  2. I lined the "ridge" inside the bucking up with the groove in the 247 mm barrel
  3. After poor results I reinstalled the stock barrel following same process above (including new barrel clip)
  4. Gun again delivers .28g bb to tree on a flat line in a "one count"
  5. Reinstalled the long barrel again following above (including new barrel clip) (yes, I ordered four with the barrel cuz I read that they tend to break and I did indeed break them every time)
  6. After a second set of poor results, reinstalled stock and again back to delivering .28g bb to tree on a flat line in a "one count"
  7. I pre-tested all barrel / hop-up combos with with the bb drop method. In all cases the bb went through bottom of hop up  and entered the bucking cleanly, and could be dislodged with the slightest pressure
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kinesis

Regular Member
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Posts: 100
Reply with quote  #2 
did you adjust hop up for new barrel?

just my 2 cents only

=)
-k
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sheywood

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Posts: 21
Reply with quote  #3 
Appreciatefeedback kinesis

Yes did adjust hop up didn't seem to help. That said, I did not check to ensure barrel was totally clean (per orig). I'll double check make sure no goop in there
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B3H1NDu

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Posts: 163
Reply with quote  #4 
Sounds like you're suffering from undervoluming.

Basically, there isn't enough air in the cylinder to properly push your BB down the longer barrel length.

May I ask why you opted for a longer barrel? Barrel length really does not matter for accuracy or range in airsoft and having a longer barrel eliminates the best things about the Vector IMO.

If you wanted better range/accuracy you should have just bumped up BB weight.
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sheywood

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Posts: 21
Reply with quote  #5 

B3H1NDu, below I answer your question, but first...

IT WAS USER ERROR. Ignore the previous chest pounding...

I was failing to reinstall the large spring that goes between the hopup and the outer barrel in all of the above scenarios. This caused a drop in FPS that presented itself severely with the longer barrel but did not present sufficiently with the stock barrel for me to detect using my unscientific method.

I saw the spring under my work bench last night and thought "Huh, I wonder if that came out of the vector...". Pulled up the Vector parts list and realized it probably did...

Larger spring and longer barrel now installed and this thing is a laser out to about 85 ft w/.28. I'll chrono at the field this weekend and report back results

B3H1NDu, re why the longer barrel

  1. I wanted to see if I could do it. Turns out that yes, eventually, I could figure it out
  2. It was driving me crazy to think there was all that potential performance in the gun I was not unlocking
  3. I chose an inner barrel and mock suppressor that only extends the overall length of the gun about 1 3/4" which is acceptable to me

And kinesis, I cleaned the barrel before the reinstall and it actually took a few patches before it came out clean, so that was needed as well

 

 

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B3H1NDu

Regular Member
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Posts: 163
Reply with quote  #6 
Good that you figured it out.

Was going to add that undervoluming wouldn't have been expected with only a 247mm barrel anyway.

If having unused potential in your gun drives you crazy, then I've got no idea how you use .28g bbs only. I'd bump it up to at least .3, .32g. You'll see a significant increase in range and accuracy.
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sheywood

Junior Member
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Posts: 21
Reply with quote  #7 
Interesting. I have a bottle of .32s. Will give them a try
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sheywood

Junior Member
Registered:
Posts: 21
Reply with quote  #8 
Chrono'd at the field today. Chrono showed 1.41 Joules using .28g BBs

Using this Joules to FPS Calculator I get

1.41J @ .28g = 330 FPS

Assuming there is no Joule creep going from .20g to .28g BBs, and the chrono would show 1.41J for .20g BB's I rerun the numbers to get the following

1.41J @ .20g = 390 FPS 

So ~390 FPS. Pretty good and about what I was hoping to see when all was said and done

And a picture below

KKV.jpg 

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