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Uses All The Gas In First 10 Shots

gas problem efficiency bolt mag use uses too much gas big problem

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#1 Mac Wynkoop

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Posted 24 October 2013 - 10:33 PM

Hi guys, I have run into a problem with my MP7. I had last used it at an outdoor game, and then put it away for a week or two. When I went to get it to shoot it again, I had this problem; When you filled the mag completely full of gas, it would expel ALL the gas in the first 10 shots, with the last three being very weak. Anyone seen this before? I suspect it's a problem with the bolt letting too much gas through, but I'm not sure.

Also, I usually run propane with shock oil as lubricant. Any thoughts or help would be much appreciated :)

Thanks everyone in advance.

#2 Chuck S

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Posted 25 October 2013 - 02:11 AM

How long are you filling the magazine.  You can't overfill them so I charge mine for about 45 seconds.

What temperatures are you shooting in?  Gas pressure drops dramatically with temperature.

-- Chuck

#3 Mac Wynkoop

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Posted 25 October 2013 - 06:06 AM

4-5 five second fills. Room temperature 55-65F.

#4 SR105

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Posted 25 October 2013 - 10:00 AM

So let's see if we can narrow it down. Is the MP7 visibly venting more gas per shot? Can you see the excessive vapor coming out of the barrel and ejection port?

If yes, then there is something wrong in the bolt. You can try applying shock oil onto the main seal inside the cylinder and see if the efficiency comes back. Your cylinder might also be cracked but this is a remote chance. I can't even remember the last time I saw a cracked cylinder in an MP7

If no, then there is something wrong with the magazine. My best guess would be the fill valve and there just isn't enough propellant going into the magazine. You can try replacing the fill valve and see if it works better.

Do you have more than one magazine? Does this problem occur with every magazine?

#5 Mac Wynkoop

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Posted 25 October 2013 - 11:08 AM

Quote

Is the MP7 visibly venting more gas per shot? Can you see the excessive vapor coming out of the barrel and ejection port?

Yes. It is clearly visible.

Quote

Do you have more than one magazine? Does this problem occur with every magazine?  

Yes. It is evident in all three of my mags.

#6 Mac Wynkoop

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Posted 25 October 2013 - 12:10 PM

Oh, I found the problem. The propane bottle I had at the last game ran out, so I bought a new one. It must have been old stock at the local gas station, because I just found that by holding it upside down and filling the mag, I got normal pressure and efficiency again. I did strip down the bolt and lubed everything up too, so that probably helped. Thanks for the tip about lubing the main seal! Thanks guys, and I'll try and become a more active member on the forums here. I just love KWA's!

#7 SR105

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Posted 28 October 2013 - 02:30 PM

That's great to hear! I love my MP7 as well and I take it out far more often than my LM4. Good luck and have fun out there!





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