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Hi, many thanks for your answer.

The explanation can be this:

 

- On my MP5Kurz, that have a very short barrel, if I put a 5cm barrel long (plus the stock) and with a diameter shorter then the stock the air flow, outing the piston, found an "exit way" more long then in the stock barrel, so the BB is "force out" for a more long time, so have more power correct?

- If I put a very long barrel the piston can do the second cycle so it can " re suck" the air flow and decreese the power to get out the BB, correct? And in this case, the penality of major friction in the barrel is higher.

 

If it is correct, can I ask, in your opinion two things:

1) About, how mutch I can increese the power with a longer barrel? the max power increese possible

2) for my MP5Kurz, whats is the best sixe to increse for get the best upgrade of power? 2cm? 4cm? 10cm?

 

thanks

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- On my MP5Kurz, that have a very short barrel, if I put a 5cm barrel long (plus the stock) and with a diameter shorter then the stock the air flow, outing the piston, found an "exit way" more long then in the stock barrel, so the BB is "force out" for a more long time, so have more power correct?

- If I put a very long barrel the piston can do the second cycle so it can " re suck" the air flow and decreese the power to get out the BB, correct? And in this case, the penality of major friction in the barrel is higher.

 

If it is correct, can I ask, in your opinion two things:

1) About, how mutch I can increese the power with a longer barrel? the max power increese possible

2) for my MP5Kurz, whats is the best sixe to increse for get the best upgrade of power? 2cm? 4cm? 10cm?

- On my MP5Kurz, that have a very short barrel, if I put a 5cm barrel long (plus the stock) and with a diameter shorter then the stock the air flow, outing the piston, found an "exit way" more long then in the stock barrel, so the BB is "force out" for a more long time, so have more power correct?

To a LIMITED extent, yes.

- If I put a very long barrel the piston can do the second cycle so it can " re suck" the air flow and decreese the power to get out the BB, correct? And in this case, the penality of major friction in the barrel is higher.

Wrong, very wrong. There is no such thing s a re-suck/suck back. AEG mechboxes draws air from the nozzle and cylinder, not through the barrel, ever in an major fashion. You have to break down the firing impulse to understand time. How far does a bb travel at 100m/s. How many cycles does an AEG do in 1 second? How long is your barrel? Knowing all three will show you that your bb has moved FAR beyond the barrel in the time it has fired.

Let's say your aeg fires 10 times a second in Full Auto. Your bb moves at 300m/s and your barrel is 200mm long.

 

A mechbox has two cycles, release and retract. So that means a mechbox fires a bb once every .05 seconds. Now with time on hand and the fps. Your bb moves 15M bevore the next shot fires....so...if your barrel is 200mm long. The bb is already in front of your barrel by 14.8M and thus it cannot be affected by any "suck" even if the system worked that way.

 

If it is correct, can I ask, in your opinion two things:

1) About, how mutch I can increese the power with a longer barrel? the max power increese possible

Depends on how ugly you want to make your AEG.

2) for my MP5Kurz, whats is the best sixe to increse for get the best upgrade of power? 2cm? 4cm? 10cm?

Turn it into a HK94 "type" and put a 365mm barrel on it. Then Change the Cylinder to a Type 2. Install a M120 spring and you should hit 410fps with .20g.

 

Other than that it is Impossible to push more air pressure out of a 200mm barrel.

Edited by Guges Mk3

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Guges Mk3, on 26 Oct 2015 - 1:59 PM, said:

 

- On my MP5Kurz, that have a very short barrel, if I put a 5cm barrel long (plus the stock) and with a diameter shorter then the stock the air flow, outing the piston, found an "exit way" more long then in the stock barrel, so the BB is "force out" for a more long time, so have more power correct?

 

To a LIMITED extent, yes.

Avoiding translation errors I understand that if I put a barrel more long the stock (few-more long.... not very mutch long) I increese power, express in Joule

 

- If I put a very long barrel the piston can do the second cycle so it can " re suck" the air flow and decreese the power to get out the BB, correct? And in this case, the penality of major friction in the barrel is higher.

 

Wrong, very wrong. There is no such thing s a re-suck/suck back. AEG mechboxes draws air from the nozzle and cylinder, not through the barrel, ever in an major fashion. You have to break down the firing impulse to understand time. How far does a bb travel at 100m/s. How many cycles does an AEG do in 1 second? How long is your barrel? Knowing all three will show you that your bb has moved FAR beyond the barrel in the time it has fired.

 

Let's say your aeg fires 10 times a second in Full Auto. Your bb moves at 300m/s and your barrel is 200mm long.

A mechbox has two cycles, release and retract. So that means a mechbox fires a bb once every .05 seconds. Now with time on hand and the fps. Your bb moves 15M bevore the next shot fires....so...if your barrel is 200mm long. The bb is already in front of your barrel by 14.8M and thus it cannot be affected by any "suck" even if the system worked that way.

OK! I read that a piston with a hole neare the front of gearbox (so, near the exiting point of air flow) can resuck the BB! OK, perfect in this way!

If it is correct, can I ask, in your opinion two things:

1) About, how mutch I can increese the power with a longer barrel? the max power increese possible

 

Depends on how ugly you want to make your AEG.

Yes... I love Kurz because it is short! And I not want to get ugly with a long long barrel!!! Maximum accpted for me is the 3cm

NOT NOT NOT This way: http://www.softairvendibene.com/immagini/Prodotti/Big/MP5_KURZ_GALAXY_G5_1_0.jpg

But maybe like this way: http://www.firearmsworld.net/german/hk/mp5/802mp5ka.jpg

for You, with a 3cm barrel long, how it can increese? and with a 5cm barrel long?

 

2) for my MP5Kurz, whats is the best sixe to increse for get the best upgrade of power? 2cm? 4cm? 10cm?

 

Turn it into a HK94 "type" and put a 365mm barrel on it. Then Change the Cylinder to a Type 2. Install a M120 spring and you should hit 410fps with .20g.

I not understand very mutch for brand and specific type of upgrade but I suppose that here, you are joke to me! :-( 365mm barrel long is more long that the barrel of a AK- dragonov or of my sig552...

120m/sec spring is too... on my kurz I suppose there is a M80 or M90 , I will break my gear box! eheh 410fps with 0.20 how mutch is.... 3J?! It is too for Italy!

So, now, leave the joke and turn seriously:
Other than that it is Impossible to push more air pressure out of a 200mm barrel.

My barrel is 200mm? I suppose that was 185mm... But maybe I'm wrong...!

this is what it was did to my MP5Kurz:

https://www.facebook.com/ateamsoftaircustom/photos/pcb.1219471121405786/1219471051405793/?type=3

https://www.facebook.com/ateamsoftaircustom/photos/pcb.1219471121405786/1219471061405792/?type=3

https://www.facebook.com/ateamsoftaircustom/photos/pcb.1219471121405786/1219471041405794/?type=3

https://www.facebook.com/ateamsoftaircustom/photos/pcb.1219471121405786/1219471068072458/?type=3

 

So,staying on topic, what is tha best lentgth of barrel that I can mount, and with this diamiters? and how increese in this way the power? Now 0.84J

Edited by holyhope

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Very nice work table.

 

I used 200mm as a generalization, yes MP5k is a 185mm barrel and thus even harder to get more velocity out of it.

 

365mm is not longer than AK (455mm) and SVD (590 based on various models). 365 is M4A1 carbine length...and is fairly common.

 

People have also installed a M120 and short stroked the piston by 2 teeth to add fps.

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Hi many thanks for your answer!

M120 is a spring that is constructed to have a speed of 120m/sec, correct?

I do not know what spring exactly was put inside my kurz, what I can do to know? The preparator (that is the owner of the nice work table) tell me that is a M80 or M90 I do not remember exactly... Indeed my Kurz shut ad 0.84-0.85J

 

V

 

People have also installed a M120 and short stroked the piston by 2 teeth to add fps.

In MP5Kurz or in normal MP5 or in pother rifle, like M4A1?

The preparator tell me that a spring too hard can get the gearbox to break... So he limit power at 0.85J with a less-hard spring

 

He do not tell me that have cut some teeth... I suppose he didn't do this jobs because he mount a piston that have a rail all iron...

 

 

Returning on topin, about barrels. I tell you 185 because I remember something similar but I 'm not sure, I suppose only!

If you tell me that you are sure that it is 185mm ok, I trust you!!!

 

I suppose that the barrel of MP5Kurz PTW is more long because it have a pice get out the rifle (for support the silencer... sorry for bad translation). Maybe I'm wrong and there is the same length.

 

1) So, can I put a barrel length, SUPPOSE about 220mm... so about 3,5cm plus the original and hide it in the same "Flash suppressor" of the PTW?

2) In your opinion, about, how can increes, ABOUT the power ?

3) for reach 1J of power, what is in yuor opinion, ABOUT the perfect barrel length? (Now is 0.85J)

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The OP stated that PDI barrels are not good, has this changed over the years as nowadays if you google on them you find a lot more positive reviews of their TBB barrels?

He only stated that the Raven line of barrels from PDI are not good. As far as I am aware, that still stands. Their regular line of stainless steel barrels is quite good as his synopsis reflects.

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