Two Form 1’s in the design phase

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Two Form 1’s in the design phase

Post by daviscustom »

Still saving up for the second stamp so I can file two at once, but wanting to build a multi cal rifle can for .308, 300 blackout, and 5.56 (with the intent of building a dedicated 5.56 later), and also a 9mm pistol can. Wanting to keep both as light and compact as is practical.

Hosts at this point will be an Ar308 with adjustable gas block and standard pistol and rifle length AR’s for the rifle can( subs and supers for the blackout, supers for the .308 and 5.56) and a Glock 19 for the pistol can (probably using subs and hand loaded heavy cast subs mostly)

Leaning towards 17-4 stainless for the rifle can (baffles and tube) or possibly 316 for the tube since I have it on hand (if I don’t just weld the stack together and go tubeless). Probably a straight forward stack of base ported and clipped cones with a brake type mount that could be made for different calibers, but also very curious about the new switchback design and wondering about flipping a few baffles around, so that would lead me back to the idea of a tube with a threaded front cap to be welded after the baffle arrangement was decided.

For the pistol can, I had been planning on K or X type baffles with a cone or two for blast baffles, but it appears there is a lot of success with clipped cones as well so that is also possible. Probably use 7075 or 7068 aluminum and 17-4 for blast baffles. I like the looks of the .45 design that is in progress, but again wonder about the effects of inverting some of the baffles.

Any suggestions or opinions on how to proceed differently are welcome.

I am not a cad user so I will have to draw my designs on graph paper as always, and I have not gotten past the imagining stage yet so no drawing to post at this time.

Who is the current favorite to host images to post on the forum these days? I see photobucket has become a pain in the rear.
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Re: Two Form 1’s in the design phase

Post by fishman »

Who is the current favorite to host images
imgur
300 blackout form 1: http://www.silencertalk.com/forum/viewtopic.php?f=10&t=137293

5.56 form 1:
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=141800&p=955647#p955647
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Re: Two Form 1’s in the design phase

Post by daviscustom »

I saw your blackout can is using K's fishman. I assume you are still pleased with the performance? How do you like it with supers? How does it compare with supers vs your 5.56 can with supers?

I am aware that some companies are using heavy duty k's for centerfire rifle even though they are normally considered to be for pistols, and obviously there are many companies using cones for pistol calibers even though they have in the past been considered to be for rifle cans. I am guessing between the sonic crack of the projectile breaking the sound barrier and the port noise from the action cycling (for a semi-auto) that it becomes difficult to discern the difference in performance between designs until they are on a bolt gun or lever gun. I guess what I mean is, on the supersonic end of things, would you (anyone) agree that we quickly reach a point of diminishing returns from design changes?.... and it is likely on the subsonic end that there might be more room for experimentation?.....thoughts?

My interest I guess would be in reaching the point of attaining good performance with supers (as much as can be expected) and excellent performance with subs for both the rifle and pistol cans. I am, as always, most interested in being as quiet as possible.....so by default I gravitate towards subs when it is practical. For .308 and 5.56 I am just focused on making those rifles more pleasant to shoot with full power loads.
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Re: Two Form 1’s in the design phase

Post by fishman »

I've never fired supers through it. Send me a case and I'll let you know how they sound :)

My k baffle 450 bushmaster can sounds great
300 blackout form 1: http://www.silencertalk.com/forum/viewtopic.php?f=10&t=137293

5.56 form 1:
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=141800&p=955647#p955647
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Re: Two Form 1’s in the design phase

Post by daviscustom »

Never have?! I don’t suppose I blame you, there is nothing terribly exciting about supersonic 300 blackout, but it would be interesting to make the comparison even though it wouldn’t really be apples to apples. I guess the only reason I have any supers is just to have another option for deer hunting with the AR pistol during the alternative methods part of the season.

So are you shooting full power loads through your k can in the 450bm?
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Re: Two Form 1’s in the design phase

Post by fishman »

daviscustom wrote:So are you shooting full power loads through your k can in the 450bm?
Yes. For deer in south Michigan, we have to use straightwall cartridges 1.8" long or shorter. Its basically a 20 gauge slug.
300 blackout form 1: http://www.silencertalk.com/forum/viewtopic.php?f=10&t=137293

5.56 form 1:
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=141800&p=955647#p955647
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Re: Two Form 1’s in the design phase

Post by ECCO Machine »

daviscustom wrote: My interest I guess would be in reaching the point of attaining good performance with supers (as much as can be expected) and excellent performance with subs for both the rifle and pistol cans.
In my experience, the best way to get good performance with both subs & supers is lots of tapered cones.

On inverting baffles, sometimes it has a positive effect, sometimes negative, sometimes nothing discernible. I've flipped the front 6 in my modular Ocelot M around, and it made virtually no difference, would have needed to fire a lot more rounds for meter averages to show a pattern beyond typical shot-to-shot deviation.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

I thought given the limited opportunity for experimentation that the inverted baffle thing might be a crap shoot, I was just hoping maybe there was some other activity going on related to that idea.

Lots of cones and a complex brake/blast chamber for FRP was the way I went for my 458 socom can.....I have enough room that I can rearrange the baffles and invert some of the stack to see what happens, but I haven't tried it yet.

ECCO have you experimented with features around the bore to create more turbulence inside the cones you plan to invert? Wondered if that might help the success rate.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

I have been thinking maybe I should change my design focus just slightly. Instead of trying to bias both cans toward excellent subsonic performance, I am considering making the rifle can all about quietest design for supers in 308, 5.56 and 300 BO..... and consider the the 9mm can to be for subs in 9mm and 300 Blackout if the 300 BO isn't going to require making the pistol can too heavy. Guessing subs in 300 BO aren't going to require anything over what 9mm would need, but that may be wrong.
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Re: Two Form 1’s in the design phase

Post by ECCO Machine »

daviscustom wrote: Guessing subs in 300 BO aren't going to require anything over what 9mm would need, but that may be wrong.
There's a bit more exit pressure and heat input, so stainless or Ti baffles would be a good idea, especially with the accompanying higher rate of fire typical of AR use. SS or Ti baffles can be made thinner, though; done right, there's only a 2-3 ounce penalty with steel and it can be a wash with Ti.
daviscustom wrote:ECCO have you experimented with features around the bore to create more turbulence inside the cones you plan to invert? Wondered if that might help the success rate.
I haven't. I'm happy with 114 dB from a 1x5.5" can.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

I've been chewing on this a while, and have ordered a bunch of Ti....tubing and round bar (all grade 5). Planning to build something TiRantish for the 9mm/300 blck sub can. In the area of 8" with about 1.375" ID. Thinking I may skew my K's a bit towards an X baffle and see if I can squeeze in a few extra baffles. Considering doing it modular so it can be more compact if desired (similar to the current TiRant).

The baffle design will likely not stray too far from the AAC design, but considering making a more aggressive raised lip/cone around the bore and trying to leave enough material opposite the scoop to have a more significant side-ways cut into the outer chamber, as well as I want to cut the port so the leading edge of the skirt port bevels to the outer chamber instead of the way I usually see it.

Feel free to put in your $0.02 and let me know if you have any other ideas.....if any of that made any sense.

Planning to build my own LID I guess, the commercially available options seem a bit clunky....and I'm a cheapskate. Like the looks of the designs T-Rex and ECCO have posted. What kind of tolerence on the piston fit? Assuming if it gets too tight it will jam up with crud.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

My thought is to use a smaller diameter ball nose endmill coming in from the front scoop side (at an angle) and possibly sweep side to side to create a port that won’t break into the edge of the skirt down below but come out the side into the coaxial chamber and create a similar size port to what the tirant baffle uses......Just further isolated from the boreline.


https://imgur.com/a/3xHob3g

The port leading to the outer chamber is not quite what I have in mind yet....hard to show accurately in a cross section. I have a CAD guy at work that may help out with some 3D modeling.
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Re: Two Form 1’s in the design phase

Post by T-Rex »

You should be able to profile the face a bit better. There's a lot of excess material in the middle. This would allow you to shorten the snout and reduce tunnel length.
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Re: Two Form 1’s in the design phase

Post by ECCO Machine »

daviscustom wrote: Like the looks of the designs T-Rex and ECCO have posted. What kind of tolerence on the piston fit? Assuming if it gets too tight it will jam up with crud.
I run the booster bore at 1.000" +.002/-0 and piston head diameter is .996" ± .001.
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Re: Two Form 1’s in the design phase

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T-Rex wrote:You should be able to profile the face a bit better. There's a lot of excess material in the middle. This would allow you to shorten the snout and reduce tunnel length.

The snout is longer on purpose to create more aggressive rim around the bore.....maybe that would be counter productive?

I need to do some revised drawings but what I have in mind will result in more than 50% of that tunnel path opening up into either the front scoop or the backside port.
Last edited by daviscustom on Fri Apr 19, 2019 10:37 am, edited 2 times in total.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

ECCO Machine wrote:
daviscustom wrote: Like the looks of the designs T-Rex and ECCO have posted. What kind of tolerence on the piston fit? Assuming if it gets too tight it will jam up with crud.
I run the booster bore at 1.000" +.002/-0 and piston head diameter is .996" ± .001.
So .004-.005” clearance..... a bit more then I expected. Do they get gunked pretty quickly?… Or do they run pretty trouble free with that much clearance?

What about the back cap?...... does the piston fit tighter there?
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Re: Two Form 1’s in the design phase

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Here is an updated drawing trying to show how I am thinking about doing the port into the coaxial chamber. May end up taking some of that upper hook out in the end but I didn’t want to open up that port too much to begin with. Think about going in with a smaller ball nosed end mill (maybe about .25”) through the front at an angle and them rotating the part on a rotary table to get a chamber shaped something like the red shaded area.

https://imgur.com/a/1mBPtnn
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Re: Two Form 1’s in the design phase

Post by T-Rex »

You need to move the waist port more towards the skirt. Easiest way, as planned, would be to bring the angle closer to perpendicular. This will bring the cutter's nose farther down the tunnel. The gas is moving toward the skirt very fast and could slip right by that entrance.
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Re: Two Form 1’s in the design phase

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Re: Two Form 1’s in the design phase

Post by daviscustom »

I'm not trying to argue, but let me explain my thought process so you can tell me when you think I have deviated from reality.

I posted a picture of the TiRant baffle, and as you can see the port (and the bottom edge of the port that divides the gas) is offset from the boreline quite a bit further...so the gas has to expand or be jetted sideways to divert out the port.

My idea is that the gas will expand anyplace it can, and when traveling through that tunnel it encounters the edge that diverts gas towards the port (right along the bore)...and you have the front scoop that is jetting into it as well.....having difficulty seeing why it wouldn't work....but maybe it wouldn't
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Re: Two Form 1’s in the design phase

Post by T-Rex »

I understand what you're trying to convey, but IMHO the theory isn't sound.Everything is moving outward, but, at the same time, forward.
The TiRant's vent cut starts almost where the face scoop ends.
The jet is almost 100% responsible for filling the low pressure, coaxial space.
Make some K's and vent the waist, but don't include the facial scoop. The coaxial space will barely be dirty.
You need to force the stream across and out or into, as it may.
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Re: Two Form 1’s in the design phase

Post by fishman »

I agree with t-rex
300 blackout form 1: http://www.silencertalk.com/forum/viewtopic.php?f=10&t=137293

5.56 form 1:
http://www.silencertalk.com/forum/viewtopic.php?f=10&t=141800&p=955647#p955647
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Re: Two Form 1’s in the design phase

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T-Rex wrote:I understand what you're trying to convey, but IMHO the theory isn't sound.Everything is moving outward, but, at the same time, forward.
The TiRant's vent cut starts almost where the face scoop ends.
The jet is almost 100% responsible for filling the low pressure, coaxial space.
Make some K's and vent the waist, but don't include the facial scoop. The coaxial space will barely be dirty.
You need to force the stream across and out or into, as it may.
I am starting to see the advantages to the way they are porting..... creates more asymmetry in the next chamber.

I assume you see I have the scoop in the face (the shaded area opposite the skirt port)
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Re: Two Form 1’s in the design phase

Post by ECCO Machine »

daviscustom wrote: What about the back cap?...... does the piston fit tighter there?
.006"-.008" diametral clearance there; The ID is .755" and I make my piston shanks .748". It's the O ring that makes it snug.

You have to keep the thermal factor in mind, don't want tolerances so close that things bind when they heat up.
daviscustom wrote:
So .004-.005” clearance..... a bit more then I expected. Do they get gunked pretty quickly?… Or do they run pretty trouble free with that much clearance?
Well, I really don't ever clean booster housings or pistons, just hit the piston shank with a little lube every once in awhile. I can't tell you what sort of round counts my demo models have, but it's a lot, never a problem with boosters not moving.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

Thanks ECCO, I had been wondering if there were o-rings involved..... I have never owned a centerfire pistol can, so I have never been into a LID assembly.

Ok, I have returned back to the TiRant roots of the design, and just shortened up the baffle length and eliminated the nesting counterbore in the front face that would require a lot of fiddling in the lathe to maintain tolerances.

The outline shows the main shape of the part and the shaded areas show the sections of the porting cuts. The radius cuts in the top face will be adjusted to maximize weight reduction in that front cup and create turbulence.

https://i.imgur.com/nQWv9GE.jpg
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