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KM4 Upgrade - New to airsoft


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#41 vic_man4

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Posted 07 October 2008 - 12:44 PM

View Postallizard, on Oct 7 2008, 10:44 AM, said:

Strange....  I only drop a PHX m140 spring, install Prometheus barrel, systema bucking and everything is stock I'm getting 500, or 499 on the crono consistently.   I don't even need a m150.

Hmmm, I would guess its because of the tight bore. Is your barrel lenght still the same Allizard and Supraracer?

#42 Supraracer

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Posted 08 October 2008 - 05:45 AM

View Postvic_man4, on Oct 7 2008, 04:44 PM, said:

Hmmm, I would guess its because of the tight bore. Is your barrel lenght still the same Allizard and Supraracer?

Mine is the 363mm it is a few mm shorter than stock. Maybe I messed the bucking up or I am not getting a good seal. I did not use the brass collar with the JBU it did not fit. Like I said new and learning. The piston felt like it had good compression. If I put my finger over the nozzle it was hard to push / pull.

I am going to check the bucking seal and re-chrony.

John

#43 Guest_allizard_*

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Posted 08 October 2008 - 03:49 PM

well.. I'm using 509.... did I mention I have a full seal cylinder too... maybe that's why you are not getting the FPS.

#44 triple b

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Posted 08 October 2008 - 09:12 PM

just to add I habe a m4a1 with a km Tn tighbore guarder 130 spring.....shoots .20 bb at 510-505 fps using a radar light crono.....with a 8.4 v battery everything else stock.....sw-computer mosfet is next

#45 Supraracer

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Posted 10 October 2008 - 04:18 AM

View Posttriple b, on Oct 9 2008, 01:12 AM, said:

just to add I habe a m4a1 with a km Tn tighbore guarder 130 spring.....shoots .20 bb at 510-505 fps using a radar light crono.....with a 8.4 v battery everything else stock.....sw-computer mosfet is next


Are you using the brass collar on your TB barrel? What is it's purpose? I readjusted the bucking need to re chrono this weekend.

John

#46 triple b

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Posted 10 October 2008 - 08:32 AM

brass collar....i just switched the barrels out thats it....same hop-up....everything else is stock my buddy has the same set-up (where i got the idea) his is shooting 540fps with .20 gram oh his piston cracked when he was changing the spring so he used a Classic Army superhard poly piston as a replacement with new o-rings....his gun hits hard.....

#47 Supraracer

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Posted 10 October 2008 - 08:34 AM

View Posttriple b, on Oct 10 2008, 12:32 PM, said:

brass collar....i just switched the barrels out thats it....same hop-up....everything else is stock my buddy has the same set-up (where i got the idea) his is shooting 540fps with .20 gram oh his piston cracked when he was changing the spring so he used a Classic Army superhard poly piston as a replacement with new o-rings....his gun hits hard.....

On the stock barrel mine had a brass collar that went over the barrel in front of the hop up.

John

#48 triple b

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Posted 10 October 2008 - 11:49 AM

yeah my KM TN tight barrel just came with the barrel only so i had to swap all the parts collar hop up....everything off the stock barrel to the tight bore...hope that answers your question....there is a good youtube video on the breakdown of a barrel change and spring gears upgrades....mechbox.com look up m4 upgrade




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