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G&P force recon m4 tb barrel upgrade

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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?




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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

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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

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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

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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)

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The gun is brand new so the bucking is mint.



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.

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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 ??

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


The standard rubber has nothing to trim.

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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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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.


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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Well last time I tried changing a spring, it cost me to get it sorted out and this g&p has a recoil system

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Go back to old barrel & stock hop unit on the shorter 220-ish barrel

coz barrel length can REALLY alter crap I just discovered.....


just got through testing about a dozen springs and interesting results.....

Also I noticed no real difference which way round the springs went either ??? which is a bit unexpected

You are supposed to fit spring with tightest coils at spring guide end to allow easier starting on irregular springs

and it is supposed to make a difference or lower fps if it goes back to front (tight coils at piston) - NOPE


For the record these springs were tested on a APS UAR that is supposed to have a full stroke 410-ish stock barrel

Some were std regular or linear or same crap coil spacing & others were irregular springs but no difference seen on either ???

(also worth noting the m100 fitted to UAR from TWG was hitting a bit over too 348 - 355 so a bit over its official 328 rating)


Also tested the old cm515 spring which was 400-405fps on 380mm barrel and it gave 405-410fps so kinda about right on 407mm


Also the Element M105 used to give me 350fps on a CM18 with a 275mm barrel with AoE done but stock spring guide

(probably hit 365fps with spring guide is my gut feeling)

But 1 - maybe 2 of these (found another in a bag of old springs that looked same) was hitting 390 to nearly 400fps on UAR

if I fitted spring guide to CM18 and expected 365 - that is still a 25 to 35fps increase on the longer barrel in UAR


Going by a list of figures n crap from these springs tested it does seem to indicate there is joule creep as barrel gets longer

(Well don't know if it is exact same joule creep as some gas guns get lifting heavier 0.25's bb's at similar or close fps to 0.20's)

But fps does seem to rise the longer the barrel gets showing an increase in Kinetic energy - lol


God I love that word and had to squeeze it in somehow coz you always see that kinetic energy crap being used in spring/fps posts etc....


What is odd that my gun was able to stay below 350 previously but piston seal might not have been 101% perfect

plus I did recently change bucking as it showed a slight nick looking where the lips where - so this may explain some stuff

(same spring, different pistons but still short stroked 2 teeth - rof has dropped a smidge but now using all bushings & bit heavier piston weight)




Springs tested - most I haven't got a bloody clue wtf their ratings are/where:


440 fps - same both ways

432 fps - same both ways

425 fps - same both ways

* my gut feeling these 3 could be m120's hitting say 30fps more on longer barrel *


410 fps - cm515 spring so sounds about same/similar fps in UAR (same both ways) - might be a m115 ????


390 - 395 - Element M105 - irregular spring but same both ways ???

385 - 390 - Element M105 - maybe - well looks very similar and probably chucked in spring bag coz unsure if 105 or 115 spring

* could be rated a m105 but might be a smidge over / worn m110 *


380 - 385 - same both ways

380 fps - same both ways

* these could be used m105 or over rated m100 ??? *

(one of these came out of a used broken G36c I'm lead to think)


340 - 345 - same both ways - Hmmmm, this could be a m95 or so spring and could come in handy later........

325 - 330 - this could be a m90 or m95 slightly worn spring......


The last 2 springs are quite possible lower springs than m100's if the Element M105 is anything to go by

These might show a small minor increase if installed say in an AK47 with 455/469mm barrel ????

So these might save me a major headache when I downgrade my cm28a AK's perhaps

(would be good to get somebody like Ian's experience on this though)


Think Sp00n had an L85 & R85 thingy majig and had to drop in a m90 or m95 spring in there (stock barrel length of 510mm me thinks)

as he was too hot to use .25's at around 310fps (aprox 350 on 0.20's - ah to hell with it - KINETIC ENERGY :)




Now I still gotta rip my box apart - pull spring out, and test this mofo that hit 385/390 even though it is short stroked 2 teeth

and then when tested in UAR try and get something 30-35 less perhaps, I'll try 30 is my gut feeling atm.....


Getting back to your own problem it seems that the 50 fps increase is half tbb & maybe half barrel length increase

Though you say you tried the old barrel I think - so the mystery deepens if you put back all the stock stuff

though the flat hop has probably pushed it up a smidge but jeez......


I'm really sorry I do not have a perfect solution other than complete stock barrel & hop,

clean barrel and wait for a bit of fps drop before doing any further tweaks - not what you wanted to hear

but just a little alteration can make a big difference I have just found out and can increase fps but so much it places us over site limits


Damn Kinetic Energy bollox


But atm my hunch, and that is all it is btw seems to show that there "might" be a 20-30fps increase when you extend barrel lengths by 100mm

This could equate to say about 8 to 10% increase in fps per 100mm but tbh this crap & my findings has proven only one thing

Trying to work out rough expected fps is a major guessing game as so many factors can alter $hit

Think I'll cancel my degree in airsoft mathematics for now coz as soon as I find something that works

another curve ball gets thrown at me and knocks me on my ar$e that I feel like an England Rugby player atm


edit/update thought or conclussion based on f*ck actual knowledge but here we go.....


G&P gun has 215mm barrel so to ensure it has a bit of oomph they bung in a m105 or maybe m110 to compensate for fps lost

You fit in 300mm which bumps it up to normal fps level of 350-360 but coz tbb it goes up a further 15-20fps

this might explain where the hell that extra 50fps came from

this is all duck speculation and end of day it don't change $hit that its running hot

but might shed some light or idea wtf all these weird figures are coming from maybe


I'm off to get some Nurofen coz I got a major headache and my own crap to sort out still

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