Waste ports - big or small

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mcrump
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Waste ports - big or small

Post by mcrump » Sun Jun 26, 2016 3:53 pm

Which is more effective, very large waste ports or small waste ports? I've seen both and have always leaned towards the smaller ports, but lately I've seen some pretty doggone large ones. Testing or opinions are greatly appreciated.
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gojckent4
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Re: Waste ports - big or small

Post by gojckent4 » Fri Jul 08, 2016 10:52 pm

Bump

quietoldfart
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Re: Waste ports - big or small

Post by quietoldfart » Sat Jul 09, 2016 12:51 am

I've tried smaller ports on my short K baffles, but did not get much dirt building up in the outer areas of the baffles even after shooting a few magazines through the silencer. When I opened these waist ports to about double the venting area and tried again the resulting mess outside the skirts was dramatically increased, while suppression was improved very slightly - as gauged by my ears and by my cheap SPL meter. So I concluded that larger was better, up to a point. Going too large, as I often did in my very early K baffles (which were twice as long and mounted in a much longer tube, so not exactly a fair comparison), resulted in poorer suppression efficiency.

I realise that smaller waist ports are strongly advocated by certain members here, but my subjective experience contradicts this wisdom so I do what works for me. I've recently completed my second compact .22lr rifle and used 13 baffles in it all ahead of the 4" barrel. 12 K baffles averaging about 0.55" long, but varying between 0.5" and 0.65" with the longer ones towards the end cap. 1 blast baffle, modelled after the blast baffle in the Dead Air Mask 22. The result is rather impressively quiet. The waist port oval opening length and width average about 0.14" x 0.24".

andromax
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Re: Waste ports - big or small

Post by andromax » Sat Jul 09, 2016 1:57 am

What sized ball mill/cutter did you use on your cuts? I've been trying to get an answer on if 3/8th" is the right size for 9mm/.357 or if I should go 7/16" or a bit larger even.

I went with 3/8" centered on the edge of the bore on my completed K baffle can and have been trying to get an answer if a bit bigger would help or hurt.

Also, have you tried the exit holes on the bottom of the cone skirts? Seems like they would be handy for draining water even if they didn't actually help suppression.
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quietoldfart
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Re: Waste ports - big or small

Post by quietoldfart » Sat Jul 09, 2016 2:49 am

I've only used a round-nosed end mill with 1/4" diameter. The distance of the plunge from the bore centre has determined the size of the vent. I've not felt any need to use a larger bit. But of course this is only for .22lr, nothing larger. Generally the bit used should probably match the bore diameter of the baffle, which in the case of mine is 0.25" for the first few K baffles and slightly larger for the following baffles.

In my earlier attempts at K baffles, the length often as much as 1.125" in total, I tried first without, then with the 'mouse hole' at the largest diameter of the cones. Suppression efficiency seemed to drop slightly, though not very significantly. I soon dropped this element as being unnecessary and weakening the cones for no good reason, besides making cleaning more challenging as it introduced another place to cut my fingers. A small Dater hole in the first baffle face seems sufficient, then just the normal waist vents and face ports after that with no tertiary holes.

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whiterussian1974
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Re: Waste ports - big or small

Post by whiterussian1974 » Sun Jul 10, 2016 1:18 am

Theoretically, a smaller waist vent in the 1st baffles would mean a longer retention time for gas trapped outside the skirt to reenter the cone.

Further down the Stack, larger holes would allow quicker Turbulent Upset off-boreline.

So Trap early, and Swirl later. But that's just 1 Theory.

Personally, I prefer a perforated face and solid skirt for the 1st 2 Ks. Then the Standard porting for the Remainder. This creates a longer lineal surface/volume for the Initial gases to traverse. Then induce Turbulent Upset later in the Stack.
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