Barrel Extension

[Old Guy]

Putting the cart well ahead of the horse, I spent a happy hour making a barrel extension/mock suppressor for my Cyma cm501 CQB. The inner barrel is a piece of aluminium arrow shaft tapered to seat into the crown of the rifle's barrel. The inner diameter is an excellent match to the rifle's barrel, it seems. The muzzle end is 'crowned and polished'.  The outer body of the assembly is made from a solidly-made cardboard inner from some clingfilm and the inner barrel is centred with rubber-bushed washers which fit snugly into the outer tube. The whole assembly gives an additional 255mm to the existing 259mm of the Cyma  giving . There is an adaptor (of sorts) to hold the tubing to the rifle's outer barrel and is stabiliser further by the flash hider.

Now the question; 

Assuming it stays aligned with the bore axis is there any point in this much extra barrel? Is it likely to (a) raise the FPS?   (b) aid more accurate longer range shooting?  (c) be just as effective (whatever that means) at half the length?

All contributions welcomed, thanks.

 

[CrackCommandoUnit1972]

Photos or it never happened.

 

[Sitting Duck]

Longer barrel = higher accuracy is a bit of a myth

I say a bit of a myth as there is "some" merit in this claim but no way as much as people think

and it it is plain wrong to assume longer barrel equals better range & accuracy etc....

Some titchy MP5k's with 140mm barrels can be more accurate than a 363mm M4

it is a lot do with the precision of it all, true, clean barrel, with no imperfections, cleaned/polished/lapped blah blah blah than the overall length

in other words - a shit barrel is a shit barrel no matter what length

Most of the performance - or rather the results is mostly down to bucking/nub

(not all of it but take this as the core foundation of performance)

other crap like bb quality, actual barrel length & stuff matters little if hop/bucking is a bit poorly

(and if it is torn/fucked then you are fucked)

FSP rises/lowers due to the creep issue

a longer barrel will increase fps in most cases but might perform poorly if your cylinder is set for 250mm

then you plop in a 455mm - you have not got enough air volume to propel the bb all the way down the longer barrel

the reverse is over-voluming, plopping a 140mm barrel in a full cylinder gun and excess air can create turbulance behing bb as it exits

(so they say, so the idea is to match cylinder volume to barrel length volume & a tbb make little difference to volume ratios

NB: I said volume RATIO's, tbb or wider bore alter volume values by a couple of percent - that's all

if a std barrel is 6.05mm and you use a 6.01mm the diameter has lessened by half a percent (6.05 x 0.995 = 6.0198))

The fps might increase a bit but VOLUME or VOLUME RATIO alters only very slightly if you bother with maths

and fuck the maths a bit unless you over think shit like me

Most of the crap is down to bucking, clean barrel & decent bb's

under say .3gms, deffo 0.25gms they have to lighten a number of bb's owing to the material used (air)

with this comes slight variations in bb weights especially on cheapo bb's

not uncommon to find if you chrono on cheap egg bb's with more air than an Aero bar

you get real fluctuations in weight say .195gms to .205gms - that is a 2.5% variation on a 0.20gm mass

(I get told off by nerds the term is mass - oh fuck off)

so no wonder you might still see fps varying a bit at chrono if everything is perfectly sealed if bb mass varies

Point is you will get flyers at times and better accuracy is attained on 0.25's etc...

The barrel is decent, if you look to tweek stuff change out bucking/nub to a Maple or something

keep it clean & decent 0.25's

by all means have a go - stuff does alter stuff

there was a MK23 pistol that had a suppressor that the moment you screwed it on knock the fps up say 35fps

and there was an AEG that had the fps increase slightly

https://www.evike.com/products/59319/

can't find the EXACT cheapo gun, but there was one that had a barrel extension/suppressor

that when fitted raised the fps like the TM MK23 pistol that is well known for this creep

Though this altered the fps this does *not* equate to increased accuracy just by boosting power/creep, the cheaper M4 had the smaller mini-deans connector on it and much cheaper, but had a barrel extension/suppressor than boosted fps

Though regular suppressors do not alter fps - these are a couple of rare exceptions

(in other words though unlikely to alter stuff much - in rare instances it "can" alter though in general it won't)

* edited as I'm always typing faster than my brain functions, does not equate to increased accuracy

(left out the NOT bit, as my brain was playing catch up)

So despite all this wall of text, it is unlikely to alter stuff much, but you might see a very minor one if very lucky

(doubt you might notice it and tbh if any DIY stuff is not of decent high precision likely make it worse)

but stick to decent bb's, and maybe a change of bucking

if you mess with stuff you will need a chrono or access to one to confirm the change in power/energy/fps/joules

or whatever reference to the bb exiting the barrel be it a peew, a Peew or a more powerful PEEEEEWWWWWW

your gun - have a tinker and make your own stuff - why not

and here is your special award for services to sticky back plastic & use of a washing up bottle...

View attachment 57144

A Blue Peter badge ?

 

[Davegolf]

:facepalm:

 

[Shaydee]

@Sitting Duck you'd deffo be talking about the STTI/ASG mk23 clones, they come with an extension in the suppressor. First thing anyone with any sense does though is remove them and fill them full of sound dampening material though Also like he's said, longer barrels being more accurate in airsoft is a myth. I'd take an upgraded MK23 with a nice 133mm PDI barrel over a 500mm stock brass/aluminium barrel any day just because of quality/consistency.

Honestly extensions are naff, they'll up your FPS a bit but not really be helping your accuracy. You'll be taking a nice one piece barrel that's consistent and whacking a nice break in the material, if this moves a little bit you no longer have a nice straight barrel and your BB goes off on a jaunt away from your intended target. I'd doubt that the inside of that arrow shaft is going to be as smooth as a machined airsoft barrel either.

Certainly +1 for DIY-ing something yourself though!

 

[Old Guy]

Thank you for that huge effort @Sitting Duck; that cost you a fair amount of time an I appreciate it. I don't have a suitable chronoscope for airsoft and so have no yardstick for measuring improvement or the reverse. As I said, I spent a happy hour pursuing my idea for the project and zero pence so it was possibly only my time I wasted. When I find the time I will try it though I feel that it is way too long and will probably droop and spoil everything so I may just shorten it. I don't really know what to do and I'm too busy building benches for my workshop to do very much else anyway.

A couple of pictures for any Doubting Thomas'

View attachment 57158

View attachment 57159

 

[Sitting Duck]

Thank you for that huge effort @Sitting Duck; that cost you a fair amount of time an I appreciate it....

Click to shrink...

paahh - that was the shortened version of me trying to explain some shit

The gun came with a ported cylinder probably for a barrel 200mm to 300mm or a smidge more

by all means mess about with stuff - it is just a toy gun after all

and better to mess with stuff on a cheapy starter than add Fairy Liquid bottles to Tokyo Marui

For the younger players not quite grasping the Blue Peter stuff

just have a go & "Try it yourself" as Neil would say....

usually we use the Duct Tape/WD40 when presented with an engineering issue

but for those not technically minded or vividly creative then most fix stuff like this:

 

[ak2m4]

What the chuff is that last cylinder? looks like a 1/3

 

[Sitting Duck]

What the chuff is that last cylinder? looks like a 1/3

Click to shrink...

I would take a wild guess the last one is for something like a MP5k 110mm~140mm type barrel

and by the bizarre long elongated slot, I'll take another wild guess at it being perhaps JG

as they like to use elongated round slotty cylinders in G36c & SIG 552's etc...

but set further back for 250mm type barrels - due to longer slot port appears in wrong place at first glance

Hence me stabbing at maybe JG MP5k or something but seen other ACM guns use elongated slots too

However it is important to remember to put the friggin' cylinder in the correct way ffs...

Have a look at the port position on this build and see if notice a potential fps issue

Was he the same tech who composed the guide on the Cybergun gearbox repair kit ???

In this day & age with mobile phones have high quality instant cameras etc...

there is no excuse for not taking a few pics to ensure things go back together correctly like say the cylinder

 

[Adolf Hamster]

i see sitting duck has pretty much covered the main points.

the only time i'd consider a longer barrel to be a boost is on a gas gun, as they tend to have a significant effect on energy (depending on the ratio of how long the original barrel is to the new barrel)

there's a few guns can get pretty ridiculous boosts like the aforementioned mk23's or WE's makarov but generally at the expense of accuracy. hpa's too, for example my mg42 is running a half-length inner barrel because that allows the pressure to be raised for good cycling without going over the energy limit. 

within the extremes of really short/really long the length is much less important than the other factors (fps consistency, hop quality, ammo quality and barrel quality) all of my most accurate guns have barrels in the 200-275mm range.

as much as a bit of good old fashioned DIY is to be commended, i'd place good money on it performing much worse than stock, even the stock machined options have reputations for poor accuracy.