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On the topic of SCAR barrels


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#1 CaptainSlug

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Posted 04 December 2017 - 08:32 AM

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Posting this here to extend the discussion out to more participants. I've been coordinating with and discussing this topic with a wide variety of people all over the community and it's clear that there appears to be a consensus developing on this topic and I wanted to perform some practical tests to see if the "Muzzle Blast" camp has more validity to their theory than the "Rifling/Dart-Spin" camp.

 

I'm using roughly the same dimensions and spacing that Heath settled on through his extensive practical tests with his Caliburn SCAR barrel. I've also made some string-free muzzle devices to use as a comparison. These devices were design to vent muzzle blast without "imparting" and spin on the dart. If these produced a positive result I can argue that the important factor has nothing to do with spinning darts.

 

scCu0Or.jpg

The one on the right worked. The one on the left didn't.

 

The SCAR barrel and muzzle-devices make only a small difference with waffles beyond 70 feet. At least as far as I can tell. Those darts are already quite stable and it appears that as a result they aren't as impacted by muzzle blast. This confirms my own experience with using those versus accufakes at three different wars.

 

However, when firing ANY lighter darts or half-length darts it's making a very appreciable impact on the reliability of dart trajectory. The only outliers become darts that have bent foam, either from prior use or bad breech feeding. I can aim at a window on my house from over 70 feet away and hit it with 34 of 36 darts. Without any muzzle device I can only manage 18 of 36 from the same distance.

SjdakL8.jpg

 

The muzzle devices are working almost as well, but since you can't adjust them up or down, it's not possible to "tune" them for different darts. That's the only benefit the fishing line is really offering. When you change the "rifling" all you are really accomplishing is changing the elastic inner diameter of the scar barrel so that it fits those particular darts better.


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#2 Edward the Assassin

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Posted 04 December 2017 - 10:07 AM

So the ones without the string works better for the full length dars?


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#3 CaptainSlug

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Posted 04 December 2017 - 10:36 AM

No, the strings work better for every type of dart so long as you adjust it, test, adjust it again, test again. Until you find the setting that works for that particular dart.

 

The device without strings was to show that I can get a positive result without strings, and without any twist in the design. I managed to accomplish that with one of the designs, but not the other.

 

The spiral hole pattern that is commonly used for paintball to accomplish the same effect probably didn't work because it's not a good surface to print. It would probably work fine as a machined feature, and that reflects some testing torukmakto4 did two years ago with looooong barrels with porting near the end.


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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#4 Meaker VI

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Posted 04 December 2017 - 11:10 AM

The device without strings was to show that I can get a positive result without strings, and without any twist in the design.


So... Team Muzzle Blast FTW!
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#5 Daniel Beaver

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Posted 04 December 2017 - 11:18 PM

The spiral hole pattern that is commonly used for paintball to accomplish the same effect

 

There's nothing particularly special about spiral porting patterns compared to linear porting - it's just an aesthetic choice. Modern tournament paintball barrels will tend to use linear porting, mainly for ease of cleaning in case a ball breaks in your barrel.


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#6 Zorns Lemma

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Posted 01 January 2018 - 05:28 PM

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[extremely 2009 voice] Due to low density variation in traditional projectiles, the center of mass is far from the nose and close to where the sum of fluid forces act, and so the projectile will tumble in flight along axes not parallel to the direction of travel. This is mitigated by spherical projectiles, but even these when rotating during travel will suffer from the Magnus effect. Thus, imparting spin to these projectiles improves stability by adding a large amount of angular momentum around the desired flight axis.

On the other hand, in foam projectiles, the center of mass is far forward from the center of pressure. Thus any tumbling motion though an axis not parallel to the direction of travel is resisted by a restoring force in the fluid field. In this case, attempting to give gyroscopic stability will have very little impact on flight stability. [/extremely 2009 voice]

 

I can't believe 10 years later this discussion is still going on.

(Regarding solving the muzzle blast issue for fishtail-inducing turbulence, I simply installed a longer barrel in my Caliburn, but I suppose kids buying kits and not in the modding hobby don't have various lengths of barrel material sitting around)


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#7 Thanhtacles

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Posted 13 February 2018 - 10:34 PM

A little late, but it's worth an interesting summary read for anyone curious

https://www.reddit.c...t_scar/dpvkttg/


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#8 An unnamed cell

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Posted 15 February 2018 - 11:02 PM

While this topic has been slightly resurrected, has anyone thought of making a noisemaker SCAR barrel? 

 

Upon firing your blaster, your opponents wouldn't know whether to laugh or run for their lives.

 

As far as I know, all you'd have to do is change the shape of the holes and incorporate vibrating flaps.

 

I desperately want this to be a thing, but don't have a 3D printer or a computer capable of running decent software. Also, sorry not really contributing anything to this discussion. no ban plz


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