My new Form 1 build

[okie]

@MistWolf @Clint

Here's a sketch of the internals. Pretty self explanatory.



All but the first baffle single clipped. At 5.5" it's not exactly a K can, but it's still shorter than average, and lighter.

So far I've only tried it on my Mk18 upper. I need to remove my 6920's flash hider so I can try it on the 16 inch, which is what my SOT tested it with.

I took a few shots sans ear pro, and it wasn't exactly pleasant, but also not painful either. But the port pop alone on a 10.3 is way past hearing safe anyways. My SOT went sans ear pro with his 16 inch upper, and he indicated it was hearing safe based on comparing it to a factory can that is a known quantity. Part of that could of course be the tone, so I wouldn't want to do that very often without good sound metering equipment to back it up.

On my Mk18, I might compare it to maybe shooting a 9mm pistol in terms of discomfort. Part of what makes me think I'm mostly hearing port pop is that I tried it with and without the distal cone (using a longer spacer in the blast chamber), and there was no notable difference, which you would expect there to be. I think once I do the same side by side comparison in both configurations on my 16" upper it's going to become apparent that there's a difference. If not I will just lose the distal cone and let the gasses from the coaxial chamber go straight into the distal space. My endcap of choice has some nice stepping, so that should help.

I also need to get out the nods and see what difference it makes for flash. Word on the street is that coaxials somehow reduce flash via some mechanism I've yet to grasp. Would be very cool if there was a notable reduction.

I can also move that unported cone anywhere in the stack, so I might try different positions and see what effect it has on backpressure.

[1168]

I can also move that unported cone anywhere in the stack, so I might try different positions and see what effect it has on backpressure.

Please do.

[Clint]

You may want to try moving the unported "transfer" baffle to position #4.
The theory being more disruptive mixing early in the stack and a little less direct path out for the bypass flow.

I can also move that unported cone anywhere in the stack, so I might try different positions and see what effect it has on backpressure.

Please do.

[okie]

You may want to try moving the unported "transfer" baffle to position #4.
The theory being more disruptive mixing early in the stack and a little less direct path out for the bypass flow.

Definitely plan on trying different positions. Funny thing though...

I actually had my SOT cut two blast chamber spacers. The one you see in the drawing, and a longer one that lets me run the can without the unvented baffle. So the unvented baffle at the end is removed completely, and the other baffles move up.

I wanted to see what the difference was between letting the gas recombine vs. just letting it vent directly into the distal chamber.

I've already tried both configurations, and I couldn't tell any difference whatsoever. I wish I had a good sound meter though. I would be very interested to know if there's any measurable difference.

But it's got me wondering if it simply doesn't make any difference where the coaxial chamber vents to. The gas is going to come out the end one way or another. I think by keeping pressure in the coaxial chamber low it encourages gas to leave the laminar column and go around. Because once the can reaches equilibrium, the laminar column will just go straight through. By keeping the resistance in the coaxial chamber lower, you're always ensuring that the path of least resistance is not the one straight out the bore.

[markm]

I've never found suppressors to sound much different at all. The only can, out of a dozen or so that we run regularly, that sounds noticeably different is the 762Sdn on the 308 bolt gun. That sucker is louder.

When we did an F1 kit, the thing I did, which didn't pan out, was leave a roomy blast chamber. Cutting metal without good machine shop resources is exhausting. So you talk yourself into the idea that 5 baffles is enough. But as I posted before, I had to go back in and add a baffle and some clips to the existing baffles.

[okie]

I've never found suppressors to sound much different at all. The only can, out of a dozen or so that we run regularly, that sounds noticeably different is the 762Sdn on the 308 bolt gun. That sucker is louder.

When we did an F1 kit, the thing I did, which didn't pan out, was leave a roomy blast chamber. Cutting metal without good machine shop resources is exhausting. So you talk yourself into the idea that 5 baffles is enough. But as I posted before, I had to go back in and add a baffle and some clips to the existing baffles.

A silencer without clips is basically a big heavy expensive muzzle brake.

[SteyrAUG]

I've never found suppressors to sound much different at all. The only can, out of a dozen or so that we run regularly, that sounds noticeably different is the 762Sdn on the 308 bolt gun. That sucker is louder.

Man, I have. In the last 20 years I've seen / heard add on cans get as quiet as MP5SD setups with the correct ammo. That is pretty amazing to me. 20 years ago you could get a .22 that quiet, not 9mm or any other handgun round.

Using standard 5.56 and .308 still gives you a ballistic crack and it will never be "pew pew" quiet, but we have come a long way. The Ti cans are also a lot lighter. Cans that almost tame 5.56 and .308 have gotten smaller and lighter.

[Clint]

It's really hard to predict what will happen due to the complex dynamics at play.

It's anybody's guess and it comes down to testing to find out.


One reason there may not be a perceptible difference between the two configurations, is the port pop may be dominating the at ear sound levels.

With an unmodified gas system, the sound levels from from the gas piston venting can easily be 140-150 dB at the ear, completely masking the 130-140 dB at the muzzle.

Once the gas is dialed down, it may be easier to detect differences.

I've already tried both configurations, and I couldn't tell any difference whatsoever. I wish I had a good sound meter though. I would be very interested to know if there's any measurable difference.

But it's got me wondering if it simply doesn't make any difference where the coaxial chamber vents to. The gas is going to come out the end one way or another. I think by keeping pressure in the coaxial chamber low it encourages gas to leave the laminar column and go around. Because once the can reaches equilibrium, the laminar column will just go straight through. By keeping the resistance in the coaxial chamber lower, you're always ensuring that the path of least resistance is not the one straight out the bore.

[okie]

It's really hard to predict what will happen due to the complex dynamics at play.

It's anybody's guess and it comes down to testing to find out.


One reason there may not be a perceptible difference between the two configurations, is the port pop may be dominating the at ear sound levels.

With an unmodified gas system, the sound levels from from the gas piston venting can easily be 140-150 dB at the ear, completely masking the 130-140 dB at the muzzle.

Once the gas is dialed down, it may be easier to detect differences.

That's what I'm wondering, too. Just need to get off my but and remove the flash hider on my 16 inch so I can give that a try.

[hi-wayman]

it would be interesting to run the tests on a bolt gun or shut off the gas completely. No port pop at all.