G&P force recon m4 tb barrel upgrade

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ikarma70

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Hi all, having just fitted a lonex 6.03x300 tb barrel into my g&p and upon testing the fps I was quite surprised by how much the fps jumped up from 330 to 380 although the barrel is a little long.

I was wondering if cutting and crowning the barrel would drop the fps by 30?

Atb

Andy

 
Try an m90 Spring, if you screw up the barrel there is no going back, but you can always pop the m100 Spring back in

 
Cutting the barrel shouldn't be an issue as I have all the tools and access to a lathe.

 
Use your APS UAR's quick change box to test out a milder spring's fps

get lowest one you can find around.....

open hot box up, test spring in UAR & compare with possible lower spring

then refit best spring back into box

other options:

AoE corrected - that may lose 10fps perhaps

replace bearing spring guide with std spring guide - maybe 15fps

lose bearing on piston head ???

the above 3 are questions or examples but tbh aoe is a wise idea

could chop off couple of coils from a spring

could short stroke it a couple of teeth

need to get her down to about 355 or less

if a smidge over leave it pre-cocked overnight

main thing if barrel is decent & hop is working & feeding well then leave it as is

then go to spring/gearbox problem

 
ok - how about this......

get a 9mm x 7mm (1mm thick) o-ring

place this around the hop at the gearbox end

(hop outer diameter is about 10-11mm so stretch o-ring onto hop/nozzle entry)

this will push the hop a minor minor smidge forward so you lose a whisper of seal

though to be honest I don't think you will lose 30fps but maybe somewhere near that

The important thing is make sure she feeds - which she should do,

(its when you push hop back to gearbox more the nozzle may not fully clear)

see if she feeds and fps drops a little

if all else fails - remove o-ring and she should be back to 380fps

if you get her down to 355 then pre-cock spring etc......

try to get a thin o-ring as possible - maybe an o-ring used to steady inner barrel

you don't want a mega thick one or mags may not clip in ok

or fps drops to 150fps if nozzle/bucking seal is pi$$ poor

worth a shot before you rip her open or power up ya tools

you can also place some tape around front of box to do the same thing

but if you got a thin o-ring like sometimes found on tbb - use that as its easier

Problem with trimming up barrel is you don't know how much you gotta cut it

and you could end up with a very very short barrel as little air is being lost on tbb long or short

(you could end up with a 229 or less barrel and may not be ideal for gun you was hoping it was gonna be)

 
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Only issue with the UAR bit is that I no longer own it, I put the money to buying the g&p, I may just put the standard barrel back in.

Thanks anyway

 
ahhhh - bummer on that spring tester gun idea.......

try an o-ring on there first

tbh 50 is a big jump - normally 15-20 is a tbb increase I'm lead to believe

I'm guessing you probably fitted a new hop bucking so either

the old bucking was a bit worn or maybe not seated/sealing properly

M100's vary lots - often a bit extra & 350 is obtainable with decent seals

(could have a m105 in there perhaps to allow for so-so stock seals)

now with good bucking seal & tbb you are up to 380

try an o-ring if you can but otherwise you may have to go back to old barrel

(clean/polish it and you probably get close to 350fps)

 
ikarma70 said:
The gun is brand new so the bucking is mint.
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Oh soz thought the tbb was fitted to an old gun and new bucking to replace old bucking on old stock barrel etc.....

Wow that is a mofo jump, was ya stock barrel dirty or something ?

50fps is a mofo jump just from tbb barrel

according to LWA spec stock is about 215mm vs 300mm

but a 50fps is a big jump all the same

 
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Latest update.... Popped the 6.08mm barrel in and fitted a namazu firefly flat hop nub and the gun is still doing 370-380 so it seems like the hop rubber is very effective.

 
Got a similar headache too

SS 2 teeth, ergh & uhm about ported/full cylinder

thought wtf shortstroke 2 teeth it will be fine to lift heavier .25 or .28's

went with a full cylinder as it was SS 2 anyway using a 407mm tbb....

bad idea - 390fps using tbb 407 prommy flat hop

355-360 on short stock 300mm barrel

crappy old dirty G&G 357mm & G&G plastic hop gives 344fps but shoots like crap

(if I clean barrel or change out hop I know I'm gonna be over)

really don't wanna rip her open - again but I know I gotta

full cylinder and outstanding piston seal has screwed me over

stock spring was easy to fit in so don't think it is a true 115/120 spring

(even left it 95% cocked overnight but hardly any drop this morning)

poxy f*cking toy guns

sorry moaning and derail your thread but I feel ya pain n wtf frustration

 
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Are you using the rifle indoors or outdoors mate ??

 
Indoors for testing, I could pop the standard nub back in.

 
Sorry mate, I worded it wrong d'oh

Are you using it for cqb or woodland as 330 ain't bad, all of mine (including cqb) fire at 340-345

 
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if you fitted the flat hop - did you use different bucking

or trimmed/turned the stock bucking

if trimmed off the bucking inside your std nub may not work correctly ??

 
Woodland as there's no cqb sites round here now.

The standard rubber has nothing to trim.

 
I would either short stroke or fit a weaker spring. A good air seal is a good thing and I wouldn't go messing with it.

 
dex said:
I would either short stroke or fit a weaker spring. A good air seal is a good thing and I wouldn't go messing with it.
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Yeah but I'm still boned with mine - put ported cylinder back in - dropped at last

390 to 385 :(

How the heck that was under 350 with that setup, but gotta be a 101% perfection seal now

(this has been a bollock-ache, bearings broke the piston snapped off - yes AoE was done)

new full metal piston swiss cheeses SS 2 teeth as before.....

erhh ummm but went with new lighter poly piston head due to heavier metal rack piston...

407mm tbb - full or old ported cylinder - went with full cylinder

somehow gain 40fps - the piston seal is only thing I mainly can put it down to

Now got my APS UAR out and testing various springs out first before I open her up yet again

brand new Element m105 produced 398fps - wtf ???

SHS M125 430fps (yeah didn't think they did the " 5 " increments)

but the m125 is kinda right but the Element M105 at nearly 400fps :blink: :blink: :blink: :blink:

No wonder crap ain't adding up - think springs must be female

coz I just don't understand them like I thought I did

especially in longer barrels (407tbb gun is similar to APS UAR tester I'm using)

I know like the MK23 gas pistol had a barrel extension which pushed it over 350 to say 400

but thought stuff like joule creep was mainly on gas/co2 stuff coz never seen weird $hit like this before

Soz gate crashing thread again

thinking of doing something easier than aeg's - like a double sided bake bean jigsaw puzzle in the dark

 
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