750mm inner barrel cons

[jssmitty96]

so im after a barrel that will go most of the way through the outer on my barret as its currently only got an m4 length inside that just reaches the end of the receiver ive found a lonex 750mm 6.01 and have been told by various sources this isnt a good idea due to "suckback" i cant get my head around the physics of the cylinder volume ect but i was thinking surely this would be fine on semi auto? then the piston isnt moveing back after each shot??

also if the 750 is no good what size would you reccomend?? the rifle is around 420 fps on .2's and i shall be useing .3's .25 minimum...
other options i have foudn ar ethe madbull 6.03 650mm and 590mm and the same from lonex in the 6.01 variety

[hapi]

Re: 750mm inner barrel cons

Unless you can ensure that the piston stops in the fully forward position then suckback will occur in a normal AEG as the gearbox can stop in any position, will be the same for any barrel over 400mm length

[North West Outpost]

Re: 750mm inner barrel cons

The piston doesn't have to be moving. Suckback starts to occur where positive pressure stops. I will work it out when I get a minute.

[North West Outpost]

Re: 750mm inner barrel cons

Right. Figures will be approximate.

Volume of a 750mm long 6.01 = 21,280mm^3

Volume of standard cylinder without sorbo, taking in consideration cylinder head and piston travel. 27,147mm^3

You need roughly 1.5 x Cylinder to barrel, so even on semi only it is unlikely to work. You would need 32,000mm^3 for it to work.

However a 600mm x 6.01 barrel gives a needed volume of (sod it I didn't write it down...lol) brb...... 17, 023mm^3 x 1.5 = 25,500mm^3 So should work.

Now what Hapi says comes into play, if you were to build it and use it on auto, you may encounter suck back. This is probably the only time you would want to consider an unvented cylinder bore up kit.

Bear in mind with a barrel that length you have to hold the gun really steady or your shots will be all over the place.

[jssmitty96]

Re: 750mm inner barrel cons

thanks mate greatly appreciated

[No1_sonuk]

Re: 750mm inner barrel cons

Also, isn't 6.01 too tight to get decent range?

At that length, I should think the BB would be trying to run along the top of the inner due to the backspin of the hop.

[North West Outpost]

Re: 750mm inner barrel cons

Fairly sure they do that anyway.

Figures worked out on a 6.01 so will alter if a larger diameter is used.

Other usual things like consistency and tolerance of barrel inner surface. BB size and consistency. Pneumatic system consistency. Follow through. Loads of things to consider.

[WTP_Trust_ME]

Re: 750mm inner barrel cons

The bb wants to leave the end of the barrel just as the piston reaches the fully forward position - surley having a barrel longer will be a disadvantage!?

The bb will start to decelerate inside the barrel which is never good...

[gijohn2]

Re: 750mm inner barrel cons

After 363mm accuracy and range isnt going to get any better

- - - Updated - - -

After 363mm accuracy and range isnt going to get any better

[WTP_Trust_ME]

Re: 750mm inner barrel cons

This was what I thought.

Wind + Gravity > 0.3g bb

[North West Outpost]

Re: 750mm inner barrel cons

The bb wants to leave the end of the barrel just as the piston reaches the fully forward position - surley having a barrel longer will be a disadvantage!?

The bb will start to decelerate inside the barrel which is never good...

Havn't you read the 6 posts from the op's to yours??

IE where I worked out for the op he will be ok for a 600 long barrel?? The bb will only slow down...ie feel suck back as that is what it is causing, when there is a loss of pressure. There needs to be enough air to make sure the bb leaves the barrel under pressure. Which means in reality you do need a little over volume.

[the_monkey]

Re: 750mm inner barrel cons

its a bad bad idea.
1, its like a 13 inch penis..may look good but of no use to man nor beast.
2, like said 13 inch penis, you will pass out every time you try to wave it around from exhaustion.
3, people will laugh at you for being a mutant
4, girls will be scared to come any where near you for fear it may break them...some boys may also run as well
5, its expensive, useless and eventually you will have to hire a surgeon to trim it back down to normal size..causing destruction to your internal parts and "gear box" that may not be replaceable.

[jssmitty96]

Re: 750mm inner barrel cons

ive gone with a 550 mm 6.01 just to be on the safe side

[WTP_Trust_ME]

Re: 750mm inner barrel cons

Havn't you read the 6 posts from the op's to yours??

IE where I worked out for the op he will be ok for a 600 long barrel?? The bb will only slow down...ie feel suck back as that is what it is causing, when there is a loss of pressure. There needs to be enough air to make sure the bb leaves the barrel under pressure. Which means in reality you do need a little over volume.

Thanks for that prof - I'll keep my insights to myself next time.