10 replies to this topic

[Thom]

Has there been any systematic study of optimal barrel lengths for different guns? I seem to remember Boltsniper doing some quick-and-dirty math, but I've not seen anything more detailed, and I'd like to have some solid (or at least semisolid) figures before rebarreling my NFs, Titan, and AT2K with aluminum. It seems to me that the optimal barrel length would be the length where the pressure behind the dart equals the pressure in front of the dart at the end of the barrel, but I admit to not having the background in fluids to calculate this.

[blister]

Search.

But, for a quick answer, NF's - 4"-5", Titan - 12"-14", At2k's (w/ turret) - 6"-8", (w/o turret) - 8"-10".

[Retiate]

Search.

But, for a quick answer, NF's - 4"-5", Titan - 12"-14", At2k's (w/ turret) - 6"-8", (w/o turret) - 8"-10".

I recall people saying the volume of your barrel should equal roughly 1/4 the volume of your plunger. That won't work with air powered blasters though, as the airtanks tend to be much smaller than the plunger, but hold lots of pressure.

For a Nitefinder, if the fit is pretty tight, 4"-5" should work.
For a Titan, if the fit is pretty tight, I'd go with maybe 15". If the fit is fairly loose, 24" is good.
I have singled 2 AT2K's, and clipped one, all of which I have used a 12" barrel. The fit on the darts is fairly loose, and they all get ranges anywhere between 90'-110'.

How tight are the darts in the aluminum? Really, the best way to do it is to test different barrel lengths until you find the one that works best.

[Thom]

For air guns, perhaps you should factor in the pressure – compare the amount of the air in the air tank and barrel. If a gun took (say) 30 psi, then you would multiply the volume of the air tank by two (for twice ambient pressure) and then calculate. I have a hunch that you might need to increase the constant from 1/4 because of the faster rate of air delivery when compared to springers.

Thanks for the length suggestions as well. (For the record, I have searched, and I did not see any systematic method for figuring length.)

[Flaming Hilt]

For air guns, perhaps you should factor in the pressure – compare the amount of the air in the air tank and barrel. If a gun took (say) 30 psi, then you would multiply the volume of the air tank by two (for twice ambient pressure) and then calculate. I have a hunch that you might need to increase the constant from 1/4 because of the faster rate of air delivery when compared to springers.

No, no... for air guns, calculate it the same way you do for springers, just pretending the pump shaft is a plunger tube and multiplying by the number of times you pump it.

I recall people saying the volume of your barrel should equal roughly 1/4 the volume of your plunger.

Aye, that was the approximate variable for one gun... it's different from gun to gun, but 1/4 is a good approximation if you don't want to figure it out exactly for every gun you own. : o`

[Vintage]

For an air-pressure gun, you would want the dart to achieve maximum velocity right at the end of the barrel.

This is not when the pressure behind the dart equals the pressure outside the barrel, but when the pressure behind the dart creates a force that equals the friction between the dart and barrel. This would be at the terminal velocity of the dart for that gun at that pressure.

With some basic knowledge of physics, you can measure the kinetic friction, but figuring out the point where the pressure equals that friction is harder, especially since the pressure is not completely consistent throughout the tank and barrel (due to the valve airflow, etc.).

Like what has been said earlier, you may just want to try different size barrels with a temporary bond such as hot glue.

[watkins]

Search.

But, for a quick answer, NF's - 4"-5", Titan - 12"-14", At2k's (w/ turret) - 6"-8", (w/o turret) - 8"-10".

You might want to change those 1's to 2's for Titan barrel length. Theres no way a dart fired out of something that short will fly without fishtailing out of control or losing accuracy in an incredible way.

[Pineapple]

Has there been any systematic study of optimal barrel lengths for different guns? I seem to remember Boltsniper doing some quick-and-dirty math, but I've not seen anything more detailed, and I'd like to have some solid (or at least semisolid) figures before rebarreling my NFs, Titan, and AT2K with aluminum. It seems to me that the optimal barrel length would be the length where the pressure behind the dart equals the pressure in front of the dart at the end of the barrel, but I admit to not having the background in fluids to calculate this.

You know, all the mathematical forumlas and calculations won't do much good for you if the barrel material you select (in your case, aluminum tubing) isn't optimally compatible with your darts.

What are the specs of the tubing? Have you already tried it in your blasters? I've tried just about anything from copper pipes to fax machine spool cores, and I've yet to find anything that can match PVC, CPVC, PETG, and brass tubing in terms of overall performance.

Did you read cxwq's article on darts and barrels? Although it may not have the exact specifics you seek in terms of a formula for barrel length, it is a "must read" when rebarreling any blaster.

Most all my rebarreling has been by trial-and-error, test-fitting barrels of different lengths and materials. The last thing I feel I need is a bunch of numbers to crunch to justify my already-nerdy desire to hot-rod a blaster.


EDIT: Hey, Vintage. Long time no see.


-Piney-

[Thom]

I did read that article, and it was very helpful. The aluminum tubing is from McMaster; CaptainSlug says that it has exactly the same ID as 9/16 brass, but a) everyone does brass, and it's hard to find it in two-foot lengths.

I'll probably end up with about two feet for the Titan, eight inches for the AT2K, and five for the NFs. I can always cut more off.

Thanks for the feedback, everyone; I guess there are probably too way many variables to do a systematic study that would apply to enough people to make it worthwhile.

[Flaming Hilt]

I'm sure McMaster would carry Aluminum in 5 & 10 foot lengths. Most hardware stores carry 3 foot aluminum lengths, and some carry 3 foot brass lengths. Look around, you probably want a medium-sized store... a mid-town Ace is probably your best bet.

Best of luck. ; o)

[Thom]

All I have is Home Depot, Lowe's, and Hector's. None of their websites list what I need; I plan to make the rounds manually with some 17/32 brass and dart tag darts before ordering anything. I haven't had any luck with longer brass in the past – I count myself lucky to have a nearby hobby store that sells brass in the right sizes. If I could find shorter tubing, that would save a ton in shipping.