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CA M15A4 SPR Issue.......

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  • 21-01-2009 7:59pm
    #1
    Chuck the Buck
    Registered Users Posts: 1,478 ✭✭✭


    Hello all

    I'm having a bit of a problem with my CA M15A4 SPR (a M16 to you and me). It's currently running at about 260fps and I can't figure out whats up with it.

    I've changed the cylinder head to a systema one (the original one is exactly the same as the systema one), I've a guarder bearing piston head in it and a King Arms M4 hop with guarder bucking and PTFE tape for a better air seal. Everything else is stock (I've an Area1000 piston but that jams in the gearbox when the spring is fully compressed so I'm using the original yellow thing, but thats another story). I've tried 90m/s and 100m/s springs in it and they give pretty much the same fps and the piston/cylinder does have a good air seal/compression so I don't think its that.

    Any ideas whats up (no CA jokes please:))?


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    #2
    Cheeky monkey
    Registered Users Posts: 1,258 ✭✭✭Cheeky monkey


    It might be one of those guns that takes an over the joule spring the take produce a normal fps. I've been told the PSG-1 is the same kinda setup but you need a low fps spring to get a high fps (I think) although knowing the guy that owns it it probably has a tight bore which would explain it.

    Although if you put some teflon take around the hop and between the barrel and hop it might achieve a better seal bringing the fps up


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    #3
    Chuck the Buck
    Registered Users Posts: 1,478 ✭✭✭Chuck the Buck


    Cheeky monkey wrote: »
    It might be one of those guns that takes an over the joule spring the take produce a normal fps. I've been told the PSG-1 is the same kinda setup but you need a low fps spring to get a high fps (I think) although knowing the guy that owns it it probably has a tight bore which would explain it.

    Although if you put some teflon take around the hop and between the barrel and hop it might achieve a better seal bringing the fps up

    I've the barrel/hop wrapped in teflon tape (PTFE) already, although I know where you're coming from with 'wrong' spring thing. My TM M4 has a tight bore, guarder bucking, G&P hop and King Arms bearing spring guide and the rest is stock and it shoots at 320fps! Any bigger spring were putting it WAY over the limit! lolz


    So anyone else (MacGuyver help!) got any ideas what might be up or do I just need a 'bigger' spring?


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    #4
    kdouglas
    Registered Users Posts: 6,414 ✭✭✭kdouglas


    Cheeky monkey wrote: »
    It might be one of those guns that takes an over the joule spring the take produce a normal fps. I've been told the PSG-1 is the same kinda setup but you need a low fps spring to get a high fps (I think) although knowing the guy that owns it it probably has a tight bore which would explain it.

    Although if you put some teflon take around the hop and between the barrel and hop it might achieve a better seal bringing the fps up

    That'd be me I assume you're talking about. PSG-1 is different to a normal AEG though, the spring is actually quite a bit longer than a normal AEG spring, so a 1J spring only gives it about 250fps.

    You shouldn't be seeing that problem in a standard AEG though.

    Have you tried checking the air seal with the air nozzle on the cylinder? Is it a stock barrel?

    This is an odd problem though. The easy solution is to try a 110 or 120 spring, but there must be something causing the fps loss....


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    #5
    Masada
    Banned (with Prison Access) Posts: 11,001 ✭✭✭✭Masada


    Have ya tried pushing the pistojnh down the cylinder to see how good the compressionis? is their any grease on the o ring or cylinder? remove all the grease and keep it spotless, then just use silicone oil and see if the seal is any better. idealy the thicker silicone oil you get with tornado grenades. i find, is the best for cylinders.

    When you push the piston down into the cylinder it should feel spongey and spring back instead of just going to the bottom. if the clean doesnt help them pick up a new o ring in halfords or similar.


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    #6
    Chuck the Buck
    Registered Users Posts: 1,478 ✭✭✭Chuck the Buck


    Im_MacGyver wrote: »
    Have ya tried pushing the pistojnh down the cylinder to see how good the compressionis? is their any grease on the o ring or cylinder? remove all the grease and keep it spotless, then just use silicone oil and see if the seal is any better. idealy the thicker silicone oil you get with tornado grenades. i find, is the best for cylinders.

    When you push the piston down into the cylinder it should feel spongey and spring back instead of just going to the bottom. if the clean doesnt help them pick up a new o ring in halfords or similar.

    Sorry should have said that in the first post - compression seems fine. Its either the springs are crap or there is an air leak hiding somewhere!


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    #7
    Masada
    Banned (with Prison Access) Posts: 11,001 ✭✭✭✭Masada


    have you checked the barrel? it could be bent or warped. try another barrel on it and chrono again.


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    #8
    Chuck the Buck
    Registered Users Posts: 1,478 ✭✭✭Chuck the Buck


    Im_MacGyver wrote: »
    have you checked the barrel? it could be bent or warped. try another barrel on it and chrono again.

    Barrel is grand, I've tried the barrel from my M4 with the CA gearbox, and vice versa. the CA GB was giving lower reading with both barrels than the TM GB so I'm guessing the spring is the problem. I'll get a new m/s100 spring of a different brand and check it again.

    Cheers for the help. :)


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