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Discussion Starter · #1 ·
Ok. To start off what what i have read/been told, i hear that the cylinder needs to be "full" (no holes in it) if your shooting a M16 lengthed barrel. My 416 came with a cylinder with an elongated hole to one side, but i replaced my 300mm TBB barrel with a 509 TBB and now people tell me that i need a "full cylinder" I think this is right, but i just need an official say in it. Whats the difference between the full cylinders and the bored out cylinders?

Now to what i really need to know. I've been reading the holy grail guide on building a DMR. He talked about balancing the volume of the cylinder to the volume of the barrel. He gave a brief explanation on how to do it but does anyone know the step by step on doing this? Also, what does he mean by drilling holes in the cylinder, when he stated you dont need a bored out cylinder if your using using anything under 600mm. Will i be ok if i just put in a full cylinder and not worry about drilling holes in it, or does drilling holes in the cylinder really make the difference?

I know a true DMR is supposed to be semi only, but i sometime use full auto to suppress or make a push on the frontlines. or time to time we play in areas that favor a short gun so ill put in my 300mm barrel. If i put in my 300mm TBB will having that full cylinder affect my gun and the way it shoots? Lastly will using the full cylinder with the 509mm TBB make full auto a bad idea? Im shooting around 400 FPS and use .2 bb's but will use start using .25 bb's

Sorry to sound like such a nub, but i want to get as much accurate info as i can so i can build my gun over the weekend and not have to take apart the gearbox for a good long time :)
 

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All a holed cylinder does is more accuratly balance the volume ratio for the barrel/ cylinder combo.

For your 509mm barrel a full cylinder is ideal and will not require any modification by your self.

What you will find if you use the full cylinder with a short barrel is your accuracy will drop a bit and also the noise of the weapon will increase by alot, this is a result of the over pressure caused by the extra air not being used to propel the BB, other than that it will not harm your gun at all.

I used to do exactly the same thing on my SPR, I had a Long Sniper upper and a Short Assault upper that I just swapped over onto my existing lower reciever, all using a full type '0' cylinder.

What alot of people don't under stand is there is alot more to it than just buying a barrel and then getting a cylinder that roughly matches the length of that barrel. You also need to take into account the internal diameter of the barrel, what weight of ammo you intend to use, as obviuosly it takes a hell of alot more air to shift a .3 than it does a .2, the over all efficiency of your system etc etc

It realy depends on how far you want to take it, as you can do as I do, and run a slightly shorter barrel, which I then tune the cylinder to the ammo that I'm using, this then gives me a little extra capacity in the cylinder which I then tune by drilling my own vent holes, that then allows the piston to build up some motive force before it starts its compression stroke, this then gives a little more fps and increases the overall efficiency of the system even further
 

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ruffles said:
I plan on using a 6.03 509 TBB and use .25 bb's. How do i find out how far up the holes ill be drilling in the cylinder need to be?
Noart sort of had a relavent question there, what fps are you aiming for?

I only use .25s in my CQB 330 fps gun, everything 350fps and above I use .28s, including my pistol, the exception being my VSR when its sprung for 500fps when I use .36s.

As for porting, if you plan on a 509mm barrel and use .28s you'll be spot on with a full cylinder as it is, no need to drill anything, if you are going to stick with .25s then i'd recommend a cylinder volume ratio of 1.75 times the volume of the barrel.
 

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Discussion Starter · #6 ·
FPS wise im allowed 410 max. ill go the .28 path and with my luck, save myself from messing up a good cylinder
Kinda off topic but when you glued the foam to your piston head. What kind of glue did you use? I just want to make sure i dont use the wrong kind and have if fall off from the abuse using a lipo.
 

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A building trade glue called ' Mitre Bond', basicaly a super fast setting super glue ( Cyanoacrilicate).

Be aware they can fall off during use in any case, Laylax make a similar thing for the VSR and they are concidered a disposable item that will inevitably fall off in the in any case as no glue can fully with stand the constant hammering :-/
 

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Discussion Starter · #8 ·
Quick question. I got to shoot my gun with the padded piston head to make the correct AOE, and with the full cylinder installed. I was shooting .2's with my 509mm TBB and i noticed the bb traveling really slow. My only thought is since the spring is a bit more compressed cause the piston is moved back to the the correct AOE, its not getting its full spring back once the gears wind it up. Would getting maybe like a M130 fix this problem? My only other guess is im losing compression through the cylinder head. :(
 

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I never would reccomend the M-Series springs to anyone. Reason being, after about 500-1000 rounds you can expect up to a 30 FPS drop. I've had it happen on me twice (First time I thought I got a lemon, then I bought another and same thing). Always go PDI springs.
 
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