Madbull barrel vs. Prometheus barrel

[LUTNIT]

Interesting thing I just ran into and figured I would post it. I just changed out my ICS M4A1 w/M203 to a CQB-R with no M203 and as such swapped the inner barrel. I had a 363mm 6.03mm Madbull second gen barrel in the gun before, occasional feeding issue and decent accuracy. I swapped it out for a Prometheus 247mm 6.03mm tightbore and my accuracy had a huge jump and my fps went up 15-20. Most people run into fps increases when they install a tightbore, but I didn't expect one from switching from one to another of the same tightness but almost 120mm shorter.

Yet another mark against Madbull in my books and another for Prometheus. The price difference isn't huge either.

The only thing changed was the inner barrel (and outer.) Even used the same hopup rubber that was in it before (Guarder clear type.) I did have to switch the piston body but kept the same piston head (this as my 4th Modify piston that has stripped on me, each with less than 2500rnds.)

My CQB upper mechbox went from 345-350 fps to 360-365fps
My outdoor upper mechbox went from 395-400fps to 415-420fps
Now I need to bring both of them down to be legal

Just food for thought, I am in love with my Madbull Noveske RIS though.

[dpvu]

Not sure this debate will ever be solved. There was that study a while ago that suggested that MB tightbores were the best in terms of "smoothness". Whatever floats your boat but I think I'll try a Prometheus on my next AEG.

[Skladfin]

Originally Posted by dpvu

Not sure this debate will ever be solved. There was that study a while ago that suggested that MB tightbores were the best in terms of "smoothness". Whatever floats your boat but I think I'll try a Prometheus on my next AEG.

you got that reversed. Prometheus got the "smoothest" bore, madbull got the "tightest" bore.

In my personal experience, Prometheus has outperformed the Madbull by a huge margin on any gun.

Prometheus > madbull

[dpvu]

Originally Posted by Skladfin

you got that reversed. Prometheus got the "smoothest" bore, madbull got the "tightest" bore.

In my personal experience, Prometheus has outperformed the Madbull by a huge margin on any gun.

Prometheus > madbull

Thanks, I couldn't recall what exactly it was. In any case, I've seen MBs improve accuracy over stock for sure but I've never been able to compare MBs and Prometheus tightbores directly.

[jesster202]

i remeber hearing around its not all aways about being the tightest bore but the more concentric through out the barrel the better it is.

[namloot]

Here is the link to those threads and some other stuff:
http://www.arniesairsoft.co.uk/forum...owtopic=146196
http://www.madbullairsoft.com/images...l%20Report.pdf
Translate out of Google:
http://www.6millimeter.info/joomla/i...=150&Itemid=42
And:
http://airsoftcanada.com/showthread....493#post815493

[Bissa]

is it possible that the cylender was too small and you were getting a minor amount of suction with the longer barrel, hence when you put in a shorter barrel the suction went away and your FPS improved?
i am new to this, but it is just a thought.

[Hectic]

EDIT: I found the link http://www.21stcenturyairsoft.com/cylinderguide.php

Originally Posted by bissa

is it possible that the cylender was too small and you were getting a minor amount of suction with the longer barrel, hence when you put in a shorter barrel the suction went away and your FPS improved?
i am new to this, but it is just a thought.

Good theory but i think the 363mm is the stock length for an M4CQB rifle and if I can find the link there is a chart or list that shows the maximum barrel length for a given cylender

[Nervikaire]

Had only one Madbull tightbore in a ''personal'' build. Not bad as they are generally cheaper than other brands but in all other builds I've done for myself, I used Prometheus. IMO, they are simply the best AEG tightbores out there.

[Jimski]

Originally Posted by Hectic

EDIT: I found the link http://www.21stcenturyairsoft.com/cylinderguide.php



Good theory but i think the 363mm is the stock length for an M4CQB rifle and if I can find the link there is a chart or list that shows the maximum barrel length for a given cylender

what about a ventilated head?
does it replace a ported cylinder?

[The Saint]

Originally Posted by Jimski

what about a ventilated head?
does it replace a ported cylinder?

No, a ventilated piston head doesn't replace cylinder porting. Ventilating the piston head only serves to ensure proper O-ring seal.

[namloot]

Originally Posted by bissa

is it possible that the cylender was too small and you were getting a minor amount of suction with the longer barrel, hence when you put in a shorter barrel the suction went away and your FPS improved?
i am new to this, but it is just a thought.

There is no such thing as "barrel suck".

First, if you have a bellows piston head, it sucks minimally on the back stroke.

Secondly, the air nozzle is disengaged from the hop up chamber by the tappet plate before the piston is pulled back, breaking the air seal, so if there was any "suck" it would come from around the hop up chamber.

Thirdly, if the retracting piston did suck from the hop up chamber, it would suck the next BB being fed up from the mag, not the BB in the barrel.

To see how a mechbox works, see:
http://www.mechbox.com/

Further more, let's take the following example, an M16 shooting at 300fps with a .20g BB at 20bps. The velocity is on the low end of AEGs and the rate of fire is on the high end.

20bbs/1second = 1bb/.05seconds (one BB fires every .05 seconds).

300feet/1second = 15feet/.05second (the BBs travel 15 feet in .05seconds)

15feet X 304.8 = 4572milimeters (convert feet into milimeters)

That means the first BB is 15feet or 4572milimeters downrange when the next BB is fired.

4572milimeters/.05second = 509milimeters/.006second (it takes .006seconds for a BB to clear a 509milimeter barrel)

That is 8.3 times faster than the BBs fire. In other words, the BBs clear the barrel in 1/8 of a firing cycle.

A waveform picture an AEG firing cycle:
http://team-titanium.com/~airsoft/AE...tricReport.pdf

Even if the piston head did fully suck while winding and the air nozzle remained tightly sealed to the hop up chamber, and did not suck the next BB being fed, the BB is still way downrange before the piston begins it's next cycle.


Furthermore, a typical AEG setup has the air volume of the hop/up barrel system to be about 58% (more or less) of the air volume of the cylinder. This has been found to provide the most efficient setup for muzzle velocity and accuracy. If the volume of air in the barrel system is too great (long barrel with a ported cylinder) the air coming from the cylinder will stop pushing on the BB before it exits the barrel. This causes a net loss of muzzle velocity and unstable BB flight characteristics. This is sometimes also known as "BB suck", though there is no actual suction, just a loss of forward pressure.

Conversely, for shorter barrels, it is more efficient to "port" the cylinder, allowing the piston to accelerate for a distance before it begins to push air down the barrel. If you just push a full cylinder (type 0) volume of air down a short barrel, the BB will leave the barrel before the column of moving air reaches it's maximum acceleration. A ported cylinder (type 1, etc) uses the wasted air space to allow the piston to first get up some speed before pushing air down the barrel. This allows the maximum transfer of energy from the piston to the air in the cylinder/barrel.

Ported cylinder setups are especially useful with weaker springs where the initial back pressure in the cylinder/barrel system could cause a net loss of muzzle velocity. Stronger springs and piston weights change the dynamics involved in cylinder type/barrel length setups.

[Styrak]

Originally Posted by namloot

A waveform picture an AEG firing cycle:
http://team-titanium.com/~airsoft/AE...tricReport.pdf

Very nice report, it has a lot of info. The main part I found useful were shots per battery and mAh per shot, and efficiency on single and auto.

[diamond_SEA]

well that solves my issues on what tightbore ill install. Promethius FTW.