M4 and CQB question

[swatt13]

ok, so i have a custom built cqb. it has a complete systema mechbox and hop up, ca metal body, crane stock, and a ras, anywho my question is, i have an m4 piston in the mech box and a cqb barrel, now i have been told that the raeson i dont have much range is because my piston is too big for my barrel.... i think this is crazy, but i dunno i thought maybe id check. ive never seen a "cqb" piston, but ya.... can anyone debunk or confirm this?

[stokes]

Its not the piston that you should worry about. Its the cylinder. The cylinder should match the lenght of your inner barrel for optimum performance.

[swatt13]

ok. well i plan on switching from a cqb to an m4 barrel length mid game, now MY concern is there shouldnt be any different parts between the two as there isnt a big enough difference betwen the two variants. an m4 piston and cylinder and a cqb piston and cylinder should be egsactlt the same, no?

[mcguyver]

I think the problem for that gun is in the hop-up. If you give it some lube, it seals up like a hot damn and back comes your range. When it drys out, your range will go bye-bye. I think it's a CA hop-up with a Marui barrel. If I remember correctly, the hop-up rubber from CA is not the best in the world and almost any other is preferable. Give that a try before you tear the mechbox open. Hop-up sleeves can be had for dirt and installed in minutes.

As long as the volume in your barrel does not exceed the volume in the cylinder, then you should be fine. G&P short barrel M4 variants come with a full cylinder and I can sure tell you they have good range, considering the 300mm or less barrels.

[stokes]

Pistons are the same. Its just the cylinders that is dependent on the lenghts of the barrel.

If you have a cqb lenght cylinder and you use a m4 lenght barrel. You will lose quite a bit of power, due to suction (correct me if I am wrong). So it is best to match the barrel and cylinder.

[swatt13]

got any tips aside from replacing the hop up sleeve? i keep hearing about sealing it with teflon tape, but i havent hear where or how.

[mcguyver]

Are you going to be at the RAAT game this weekend? Give me the gun and I'll show you what I mean about the lube.

I think replacing the sleve is still the best option and the easiest to do. You could always try soaking the sleeve in some silicone oil and let it absorb some.

[swatt13]

yup.
but to clarify CAN your piston and cylinder be TOO big for the barrel?

[mcguyver]

Not that I've ever seen.

Years ago, when I used to build sub boxes for car audio applications, the ported boxes we built had specifics about port diameter and length. These were engineered to accomodate the "bore x stroke" of the subwoofer itself and larger diameter ports needed to be longer. This was done to control resonance of the system and reduce standing waves, which could either be contructive (additive) or destructive (subtractive) at varying frequencies. This was not good as they tended to be unpredictable.

As this relates to AEG barrels, I don't believe that this could happen, considering there is really no frequency variations, so standing waves are not likely to occur.

If there volume of air in the cylinder is greater than the volume of air in the barrel, then that cylinder air volume will be completely discharged out the end of the barrel along with the bb. A smaller cylinder volume means that the air will not be fully discharged out the barrel and velocity will be greatly reduced as the bb is already decelerating before it even leaves the barrel.

[swatt13]

ok, thanks guyv. that clears up one myth.