Is there such a thing as too much barrel?
 

So, had a long discussion today about cylinders and what to get for X barrel size etc etc.

Now I'm about to kick myself after this discussion because I have a sneaking suspicion that I screwed myself over with getting the biggest freaking barrel possible.

For a V.2 mechbox, a full non-ported cylinder is rated for a barrel between 451 - 550mm Inner Barrel. As stated on WGC - Prometheus type A cylinder

Now... what will happen if the barrel length is beyond 550mm? Let's say 650mm (what I bought). To me this means that the piston will cycle and finish its cycle 100mm before the BB has exited the barrel. Hopefully on full auto it won't then begin cycling back before the BB has left since I believe this would put negative pressure in the inner barrel thus slowing down the BB.


I could be completely wrong though. So what do you guys think. Is there such a thing as too much barrel? (the stuff arrives monday or tuesday so I'll be able to test it out after that point).

My opinion, as long as your cylinder isn't ported, you should be fine. But see my initial reply. ;)

http://www.airsoftcanada.com/showthr...ht=barrel+suck

http://www.airsoftcanada.com/showthr...ht=barrel+suck

http://www.airsoftcanada.com/showthr...ht=barrel+suck

just search barrel suck, loads of info on it

but I belive 590mm is a big as you can go on a standard AEG cylinder. the 650mm i belive requires a bore up(and a bore up likes a PDI 190%, i think, cant rember)

if the volume of the cyl is too small compared to the volume of the barrel, your mechbox may not push enough air to keep the pressure high by the time the pellet reaches the end of the barrel.

Imagine a hydraulic AEG which pushes a syringe filled with water into a barrel with a bb leading the water. Assume no leakage around the bb. If the syringe had a smaller volume compared to the barrel it wouldn't push enough water to push the pellet to the end of the barrel.

The situation is kind of similar in an AEG except that air is compressible so you need an even larger syringe volume because the system operates at pressure (the air initially starts at 0psig). Not having enough volume would have the pellet drawing the pressure in the cylinder and barrel below atmospheric pressure for the last bit in it's travel so you'd actually see muzzle velocities drop if you increase barrel length past a certain point.

I believe this is the proper description of the term "barrel suck".

A couple years ago I compared the ratio of cylinder volume (volume ahead of the port) vs. barrel volume and noted that matched cyl-barrel pairs had the same volume ratio for each TM AEG so I strongly suspect that good old Marui had done some design work of their own to determine an optimal ratio. I didn't end up confirming it myself as I had other stuff to do, but someone could test an AEG by starting with say a M4 cyl and keep trying longer and longer barrels starting from an MP5k up to a 650mm PSG barrel while measuring fps.

hahah... Droc dug up a some of my dusty musings.

I have seen barrel suck in action....

katey had lost the screw off my g3 - sg1 while upgrading it the night before. In a bind she grabbed the mech box and lower receiver off the g3-sas because it would be a simple 3 bolt solution. fired it in the shop, and bb's are coming out... bring it to flag raiders the next day and the damn bbs wouldn't even make it to the targets. katey had forgotten that the sas cyclinder was ported and this was before I had started working on guns so I didn't realise there was such a thing.

Fortunately for me, like always I brought a back up. You can see me using my spas-12 shotgun in my sig, that was that day.