20 replies to this topic

[Mattf]

I did a search for a like topic, but did not come up with anything.

Anyway, I've been thinking about my Nerf modifying, and I was wondering about barrel length. I see lots of people using upwards of 4" for their barrels, and I think this is a waste.

Let's think about it. Even if you can get your 1"-3" dart to the bottom of the barrel, it still has to travel a good distance before it can leave the barrel. In the time it is traveling this length, the pressure difference between plunger (I've been thinking about my NF, but I reckon this applies more or less universally) and the barrel changes as volume of air behind the dart is increase. Think about it. More space to fill behind the dart because you have a long barrel, less and less pressure behind dart.

Eventually, with a long enough barrel, you might see a "backfire" or sorts, or a negative pressure that actually pulls the dart back towards the gun.

Some will argue that barrel length increases accuracy, but what good is some accuracy when you can't shoot 30'?

I would recommend 'nesting' a short piece into something wider if you want accuracy.. This way, you won't get air sucking back on the dart. If we had huge plungers, I doubt this would be a problem. Air pressure guns may work otherwise, but I don't know.

What do you guys think?

[techtargetmaster]

Four feet for a barrel is f**king ridiculous.

~~~TTM~~~

Edited by techtargetmaster, 20 February 2006 - 07:32 PM.

[GeneralPrimevil]

Umm...where'd you get 4'?

<EDIT> Also, it isn't that rediculous. A ball gun homemade I'm working on has a 4'x1" PVC barrel. It also uses propane combustion, but still.</EDIT>

Edited by GeneralPrimevil, 20 February 2006 - 08:03 PM.

[davidbowie]

4:1 ratio. According to the almighty boltsniper, this is the point where all the air from the plunger is being used.

Also, have you seriously never heard of nested brass?

[Doom]

Neat that you searched, but whatever you searched for obviously wasn't a good term. I remember talking about this in detail quite a while ago. I'll pull up the thread for you: http://nerfhaven.com...wtopic=4618&hl=

Hopefully what is discussed will help answer your questions.

[Mattf]

4:1 ratio. According to the almighty boltsniper, this is the point where all the air from the plunger is being used.

Also, have you seriously never heard of nested brass?

Neat that you searched, but whatever you searched for obviously wasn't a good term.

Ah. I must have been searching in only one board; sorry.

Have heard of nested brass, but why don't that many people use it then? I only see it once in a while. But PVC and CPVC is all over the place...

I've seen that ratio in another hobby, the spudgun hobby.

[cxwq]

Have heard of nested brass, but why don't that many people use it then? I only see it once in a while. But PVC and CPVC is all over the place...

^ NHQ reader.

[NinjZ]

You're missing a few key points here. Longer barrels also make the stefan more accurate, period. I don't know where you are getting your calculations from, but I have seen this through trial and error and can definately say longer barrels to make blasters more accurate. Also, my mods dont suck. My blasters shoot farther than 30'.....Keep in mind it's all situational and not always true for one blaster or antoher. You also obviously havent read enough. The number one first rule of modding is you can only use materials that suit your own personal needs. Not everyone has the same brands of foam and pipeing. Not all of us have access to various sizes of brass, or CPVC or even the different kinds of PVC. As such, not everyone is going to use telescoping brass. PVC and CPVC are the most readily available barrel materials formost people so you will see them more commonely used. You would also only use telescoping brass on blasters that use larger volumes of air, not smaller and weaker springers.

You have much to learn.

Edited by NinjZ, 21 February 2006 - 12:02 PM.

[davidbowie]

4:1 ratio with a spudgun? That's crazy inefficient. Combustion or pneumatic, that's way more chamber than you need.

[ompa]

Well, once you put a 2" barrel on a Maxshot, X-bow, or other such gun, and it works as well as our 8-10" barrels, you let me know. While I'd love to have shorter barrels, it just doesn't work. Even a NF should use at least a 3" barrel.

And the only way you'll end up with a "backfire" would be if the pressure inside the barrel is less than the pressure outside the barrel; and unless your dart has an airtight seal, and while traveling maintains that airtight seal, you won't have that effect. While it might happen with something like CPVC, the barrel material is too tight to allow the dart to move far enough in order to create such a suction.

~ompa

Edited by ompa, 21 February 2006 - 07:19 PM.

[m15399]

Combustion or pneumatic, that's way more chamber than you need.

4:1 is completely reasonable for a pneumatic cannon.

[davidbowie]

...not necessary though. It works, but slapping a longer barrel on there will increase performance quite a bit. It ends up just taking longer to fill. You're wasting a lot of power. I like to stay somewhere between 1:1 and 2:1.

[m15399]

I'm not going to say that you are wrong, but that is not necessarily true. Depending on the payload, 4:1, 8:1, or even higher may get better performance than 1:1-2:1.

[davidbowie]

It WILL get higher performance, just not enough to warrant all the extra air.

Even if you're launching a solid 2" lead bar, it's the same deal.

I feel bad for hijacking the thread, but it didn't really seem very enlightening to begin with.

[Mattf]

Well, once you put a 2" barrel on a Maxshot, X-bow, or other such gun, and it works as well as our 8-10" barrels, you let me know. While I'd love to have shorter barrels, it just doesn't work. Even a NF should use at least a 3" barrel.

But don't those such guns have huge amounts of air propelling the gun? I'm talking about the smaller pistols and the ones with the liquid gauges.. Particularly on NHQ I've seen a lot of guns with long barrels, including NF's. I'll agree that 3" is a minimum though.

^ NHQ reader.

Yes... They have a lot of posts and stickies to read through, and I've spent time doing that...

Edited by Mattf, 21 February 2006 - 09:49 PM.

[ompa]

An AT2k? There's no way in hell you're going to have an effective barrel shorter than 4" on that thing, singled, or with the turret.

Even with some of the smaller pistols like the TTG and NF, just trial and error shows that such barrel lengths as shown on sites like NH that barrel lengths such as 4" are warrented. While your reasoning may make some sense, trial and error unfortunately proves it wrong.

I use NHQ as a kind of online comic; the majority of the posts there are useless, hence why they have so many of them. Alot of the threads turn in to funny flame wars.

~ompa

Edited by ompa, 21 February 2006 - 10:05 PM.

[m15399]

It WILL get higher performance, just not enough to warrant all the extra air.

That is a matter of opinion! It's reasonable if you want good range.

[davidbowie]

I'm talking a distance of 10-20 feet. While that may be big in nerf, it's not with spudguns.

Anyway, to each his own.

[rotoryfan]

An AT2k? There's no way in hell you're going to have an effective barrel shorter than 4" on that thing, singled, or with the turret.

Even with some of the smaller pistols like the TTG and NF, just trial and error shows that such barrel lengths as shown on sites like NH that barrel lengths such as 4" are warrented. While your reasoning may make some sense, trial and error unfortunately proves it wrong.

~ompa

i can't flat out say you're wrong, but you're not entirely right. my AT2K is using 1 crayola barrel, jammed in to the original barrel, and i'm consistently getting about 55-60 feet, which isn't bad at all considering. the only thing i did to the crayola barrel was saw off about 3/4'' from the back to improve airflow. i don't even shove my darts down the barrel. i like the stock micros, they're easier to find and more durable. i let the suction cup stick out the end. even w/o the crayola barrel, i get an easy 40'.

as far as longer barrels go, mattf, when a dart exits the barrel, what happens? all the air is released, and the dart loses power instantly. with a longer barrel, the dart maintains a steady velocity all the way down the barrel, unless the barrel is more than a foot long, which doesn't often happen anyway.

and brass is probably the best material for longer barrels, because of this, combined with its low friction properties. for a NF, i think that a 5'' barrel total is good, and PETG is a good material for it

[J cobbers]

i can't flat out say you're wrong, but you're not entirely right. my AT2K is using 1 crayola barrel, jammed in to the original barrel, and i'm consistently getting about 55-60 feet, which isn't bad at all considering. the only thing i did to the crayola barrel was saw off about 3/4'' from the back to improve airflow. i don't even shove my darts down the barrel. i like the stock micros, they're easier to find and more durable. i let the suction cup stick out the end. even w/o the crayola barrel, i get an easy 40'.

as far as longer barrels go, mattf, when a dart exits the barrel, what happens? all the air is released, and the dart loses power instantly. with a longer barrel, the dart maintains a steady velocity all the way down the barrel, unless the barrel is more than a foot long, which doesn't often happen anyway.

On your modded At2k, 40-50 feet is nothing for this gun. You should plug the pump, and remove the air restriction if you havent already. At2K's are capable of reaching 70+ feet with a muti-barrel replacement and even farther when single barrreled.

I will contest your assertion that stock micro's are more durable. A stephan is made of a solid chunk of foam, were as stock darts are hollow, which allows excess air pressure to build up and rip through the side of the foam. Second, stock dart tips do not stay in place for long, where as a hot glue tip is embedded into the foam body of a stephan assures that it will stay in place longer. Also because Stephans are able to fit all the way down your barrel they will be exposed to a higher air pressure when they fire and thus increase your range. This is why we have longer barrels.

Also back when I first got into nerfing, (about 6 years ago as an undergrad) I had a literal rocket scientist (i.e. grad student friend in the aero space engineering program at Univeristy of Wisconsin Madision) explain why simply adding a longer barrel to a nerf gun increases range so drastically even if you do not increase the over all power. What I mean to say is the following explains that darts to not have a constant velocity as they move down the barrel but actually acceleate until they leave it.

It works like this;
1) assuming a low ammount of friction is acting on the dart as it moves down the barrel the expanding air behind it acts like a spring, pushing the dart forward until the pressure in the barrel is equal to that of the atmosphere. Thus the dart is accually being accellerated through the entire lenght of the barrel until the pressure behind it can no longer over come the forces of friction and air resistance.

2) Continuing the spring analogy If the barrel is too long (i.e. the volume of the barrel is greater than the volume of air acting on the dart once reduced to atmophereic pressuer), once the dart to passes a point where the air pressure is equal on both sides, a deceleration effect takes place. Basically once the dart passes the equalibrium point and still has not left the barrel, it creates a vaccume behind it which slows it down, and you actually loose pressure.

In theory what all this means is that in theory if you can calculate the volume of air moved by a gun you should be able to use that to calculate the length of of your barrel for your gun. Pi x r^2 x length = volume as we are dealing with cylinders.


In air pressure guns you must calculate how much air fit inside the pump and multiply that by the number of times you can pump the gun. Use that as the volume for your barrel when calculating maximum length. Of course you'll want to take into consideration that friction and air resistance will use up some of the energy from the air pressure acting on the dart, and so you should not use the full
lenght from you barrel calculation. It is safe to say that if you subtract a few inches from your final calcualtion you should be ok.

For a spring based gun the maximum lenght for a barrel material is the same, figure out the volume of air moved by the plunger, and use that figure to determine barrel length, and take off a few inches to cover for friction and air resistance. Keep in mind that a spring gun does not use the full volume of the plunger tube, measure from where the plunger is fully retacted to the front of the plunger tube (barrel end).

[Nerfster12345]

It also uses propane combustion

Insane.I want to here the ranges when its done.FIRE FIRE FIRE!!