Two Form 1’s in the design phase

Yes, it can be legal to make a silencer. For everything Form-1, from silencer designs that are easily made, to filing forms with the BATF, to 3D modeling. Remember, you must have an approved BATF Form-1 to make a silencer. All NFA laws apply.

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Re: Two Form 1’s in the design phase

Post by fishman »

I have two titanium taper endcaps. No problems with griffin taper brakes.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

Thanks for the reply, I was just a little concerned that with hardened 17-4 only being in the low 40’s that there might be issues when it was locked down on the taper. Those brakes are nitrided though right?.... that would be basically like case hardening.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

I am considering using A2 for my blast baffle and doing a differential heat treat that would only harden the tip of the cone around the bore to slow erosion. I could also use it for the mount/flash hider and make the tapered surface harder than 17-4 ever could be..... it would have to be tempered to keep it from being too brittle if the whole brake was hardened..... or could try to just harden the taper and let the heat of a mag dump harden the bore. A2 is pretty nice to machine, would just have to experiment a bit in the heat treating
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Re: Two Form 1’s in the design phase

Post by Capt. Link. »

daviscustom wrote:I am considering using A2 for my blast baffle and doing a differential heat treat that would only harden the tip of the cone around the bore to slow erosion. I could also use it for the mount/flash hider and make the tapered surface harder than 17-4 ever could be..... it would have to be tempered to keep it from being too brittle if the whole brake was hardened..... or could try to just harden the taper and let the heat of a mag dump harden the bore. A2 is pretty nice to machine, would just have to experiment a bit in the heat treating
Zone hardening via induction heat has many uses. Use Inconel and forget the A-2 x 17-4 heat treat debate. :lol:
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Re: Two Form 1’s in the design phase

Post by daviscustom »

Capt. Link. wrote:
daviscustom wrote:I am considering using A2 for my blast baffle and doing a differential heat treat that would only harden the tip of the cone around the bore to slow erosion. I could also use it for the mount/flash hider and make the tapered surface harder than 17-4 ever could be..... it would have to be tempered to keep it from being too brittle if the whole brake was hardened..... or could try to just harden the taper and let the heat of a mag dump harden the bore. A2 is pretty nice to machine, would just have to experiment a bit in the heat treating
Zone hardening via induction heat has many uses. Use Inconel and forget the A-2 x 17-4 heat treat debate. :lol:
Well the price (free) is right for A2, and it is WAY easier to machine....not stainless but it will get blasted clean periodically. I don't know the process, but doesn't inconel require some sort of heat treating too?
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Re: Two Form 1’s in the design phase

Post by ECCO Machine »

I'd say forget all of the above and use 440C, run a low temperature temper or just leave it full hard.

Not that 17-4 suffers that much erosion anyway, but 440C is way harder and a good bit stronger. It's a pain to weld, likes to crack, but if you're not welding, that isn't a concern.

I did use all 440C with a 550° temper in my Furtivus .458 prototype, which is a fully welded core. So far, no issues with the welds.

Another good material is 422 SS. Gets harder than 17-4 with similar mechanical properties, and is designed for use in environments up to 1,200°F. Weldablility is still not as good as 17-4, but my Accipiter 375 prototype has been doing just fine on my .375 RUM, and that's a tubeless design

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Re: Two Form 1’s in the design phase

Post by T-Rex »

I'm not a huge fan of most of the Martensitic steel in the 400 series. At least not for the applications my work would apply. I say this because environments are similar to the interior of a suppressor. I'm not saying they aren't good steels, just that I wouldn't choose most for our purposes. If we were choosing a martensitic, I'd go with any of the maraging steels (cost and availability aside). They cut good, weld good, are super strong at both room and high temp, and are easily aged. I just don't like the higher carbon contents of the aforementioned 422 and 440C (personally I'd go to 440F). There's no reason to use more carbon. Strength can be achieved in other ways and, IMO, only brings drawbacks. Ecco mentioned welding. Yes, this is a downfall to the 400's. Also, even though it can be treated semi-easily, add welding to the lot and you need to be careful. Too many variables and processes.

Something we haven't brought up in these discussions is surface finish. Get a very smooth finish and erosion will take longer to start showing. Ground and polished would be ideal.
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Re: Two Form 1’s in the design phase

Post by Capt. Link. »

Free A-2 is hard to beat. I can supply various chrome molly metals plus 416 SS for the learning curve.I'll try to find some inconel for blast baffles.Do you have access to induction hardening equipment?
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Re: Two Form 1’s in the design phase

Post by daviscustom »

No induction equipment, the bonus with the A2.... aside from working with it regularly and lots of free drop to play with, in thin parts like a baffle it would take little effort with a torch to heat the bore to red and air cool. It will have some scale but once it is tempered I can clean it up and polish the front face to a mirror finish. All of our heat treating at work is farmed out so we aren’t set up to do it “right”.

At this point I don’t plan to do any welding in this can unless I get a wild hair on a design idea that requires it.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

I know I have seen the discussion on other threads, but what do you think I can get away with for skirt and minimun thickness in general on these K baffles? They are going to be grade 5 Ti and the can will be intended for 9mm, 300 blk.....does .030" thickness seem safe? I was originally thinking .050", but I am thinking about isolating the blast baffle from the K stack so that would take a lot of the impact off the K's.
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Re: Two Form 1’s in the design phase

Post by ECCO Machine »

daviscustom wrote:I know I have seen the discussion on other threads, but what do you think I can get away with for skirt and minimun thickness in general on these K baffles? They are going to be grade 5 Ti and the can will be intended for 9mm, 300 blk.....does .030" thickness seem safe? I was originally thinking .050", but I am thinking about isolating the blast baffle from the K stack so that would take a lot of the impact off the K's.
It depends on the design of the baffles. If they're conventional "open" Ks, the tension of the caps and the pressure of the blast is trying to compress them, so the skirts & flanges need to be stronger. If they shrouded, the shroud bears that compressive load, so the baffle itself can be much less substantial.

The skirt would have to flare at the front to open up, which the tube largely prevents, so it can be fairly thin. The area of concern is the waist, or the thickness left at the face flange after trepan or kidney bean cuts are made. This is where it can break away. That is where I ran into issues with 45° K baffles; they allowed me to get the scoop further in under the vent, but they had such a small waist, they had to be substantially thicker to prevent flange breakaway.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

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This is close to what I am thinking at this point.
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Re: Two Form 1’s in the design phase

Post by T-Rex »

I want to say .030 should be fine, especially with the angle of your design, but I'd probably cut closer to .045.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

Yeh that feels like less of a stretch.... and the thinner it is the more hassle it will be machining. I just want eliminate unnecessary weight where I can.

Thanks for the input!
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Re: Two Form 1’s in the design phase

Post by ECCO Machine »

daviscustom wrote:Image
The design is mechanically strong, but man, that's a lot of low pressure space and quit a bit of "tunnel" through each baffle, with not a lot of volume inside the short cones. I don't know how that's gonna work out for you.

After numerous iterations, I settled on K baffles having 60° cones with a 15° taper on the front side of the flange. The snout of the cone portion is .130" proud of the flange rim to give just enough tunnel that the scoop doesn't get into the cone and create an oblong bore. This design does mean cutting the vent from the front, though.

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Re: Two Form 1’s in the design phase

Post by daviscustom »

I hadn’t noticed the tunnel being long. Certainly compared to yours it goes on forever, and it is longer than the TiRant.....but the TiRant bore is quite a bit longer than yours. I have no idea which is better since this is my first attempt at a K/X baffle I will work on shortening that up.

When you are saying I have a lot of low pressure space you are referring to the coaxial space outside the skirt correct? Do you think I have too much space allocated out there? My theory was the more space there was available, the less resistance there would be to filling it....maybe I have gone too far. The smaller space inside the cone is increased by extra space in the face of the next baffle (somewhat). I was hoping it might balance out and give me the chance to create a larger coaxial space.

You think it is counter productive creating a more aggressive scoop on the front face? I just assumed the more that scoop could grab the better it would work.

I consider the porting on that drawing to just be a work in progress.... still a lot of head scratching to come

If you have tried something similar to what I am proposing and it didn’t go well.... by all means save me the heartache.....but on the other hand I’m not opposed to venturing out a little if you haven’t gone this route. I do value your opinions because you have more experience than I, so if you think you can extrapolate from similar experiments please do.
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Re: Two Form 1’s in the design phase

Post by HOLLIS »

In the occasion that you are taking a gander at the diminish left hand some section of the Tirant astound %you could scarcely detect the highest point of the inside track slice coming up close entrance face of the confuse getting it plunks down in the drag about a similar separation as the width of that entrance degree face.
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Re: Two Form 1’s in the design phase

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HOLLIS wrote:In the occasion that you are taking a gander at the diminish left hand some section of the Tirant astound %you could scarcely detect the highest point of the inside track slice coming up close entrance face of the confuse getting it plunks down in the drag about a similar separation as the width of that entrance degree face.
Guessing you are using a translator application..... not certain what you are saying, but I think you may be referring to the slight hook on the front scoop at the boreline on the TiRant baffles.... if that is what you are pointing out, I have noticed it, and plan to make mine similar.

....maybe you are referring to the plunge cut they use on the vent side, and how it comes up close to the back of the front face of the baffle with significant overlap of the front scoop.....not certain what you are trying to tell me. Maybe you can clarify.
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Re: Two Form 1’s in the design phase

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Has anyone built a form 1 modular can?..... or is the general consensus that that is not allowed unless you are an 07/02? My hope was to do a 9”ish can with the front 3” or so of the tube being a second section that could be removed ( along with the baffles that were housed within) and the front cap installed on the main tube for a shorter “ K “ configuration.

I was thinking.... looking back through the cobwebs that someone had done a modular, but not sure
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Re: Two Form 1’s in the design phase

Post by T-Rex »

I have and I know others have. There's nothing that says you can't, and I have an approved form to make a silencer, is my reasoning.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

After a quick search it appears there have been people that claim they even submitted prints of modular designs with there form 1 paperwork that were approved. I would think as common as it is these days it shouldn’t be an issue as long as unused parts couldn't be assembled into a second suppressor.
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Re: Two Form 1’s in the design phase

Post by fishman »

as long as unused parts couldn't be assembled into a second suppressor.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

What do you guys suggest for tube wall thickness in addition to the major thread diameter. Trying to decide on the smallest safe diameter at the rear of the tube where the end cap screws in. I am using 7/16-28 2a threads. I would like to keep the O.D. At 1.5” but .03” wall thickness sounds a little thin (grade 5 Ti). The rear face of the tube will be tapered (10 degrees off of square) will screw into a mating taper on the face of the rear cap shoulder that should help prevent the tube from expanding under pressure. This is a can for 9mm/300 blk subs.

If I am doing the calculations right min. yield pressure is 6k at .03 wall thickness.....but I guess that is assuming a sealed vessel right? Does yield mean failure or just expansion?
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Re: Two Form 1’s in the design phase

Post by ECCO Machine »

daviscustom wrote: Wed Jun 19, 2019 12:56 pm What do you guys suggest for tube wall thickness in addition to the major thread diameter. Trying to decide on the smallest safe diameter at the rear of the tube where the end cap screws in. I am using 7/16-28 2a threads. I would like to keep the O.D. At 1.5” but .03” wall thickness sounds a little thin (grade 5 Ti). The rear face of the tube will be tapered (10 degrees off of square) will screw into a mating taper on the face of the rear cap shoulder that should help prevent the tube from expanding under pressure. This is a can for 9mm/300 blk subs.

If I am doing the calculations right min. yield pressure is 6k at .03 wall thickness.....but I guess that is assuming a sealed vessel right? Does yield mean failure or just expansion?
How thin you can go depends on your ability to thread precisely.

For such low pressure rounds, you really don't need much. .015" wall would easily contain it, but you can't thread that. .035" wall tube with 36 pitch threads splits the difference in single depth vs remaining wall thickness at root. I use exactly this not only with my rimfire and pistol models, but also with Phantom 8, a 300 Win Mag rated ultralight hunting can.

Phoenix XLV, a pistol can with that .035" wall tube, I torture tested with full auto, including .308 from a 13" barrel, to the point that the aluminum baffles were liquified. The thin Ti tube with those fine threads held.

I don't know where you're finding thin wall gr. 5 tube, though. I use gr. 9 CWSR, readily available in many, many sizes from Tiger titanium.

Yield strength is the point at which the material permanently deforms. Ultimate strength is the point of failure.
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Re: Two Form 1’s in the design phase

Post by daviscustom »

It isn’t very thin wall tube. It is 2mm wall I believe.... 1.34ish ID and 1.57ish O.D. I made the rear cap with 1 7/16-28 threads..... so sounds like you would be more than comfortable with .03” meat left on the tube since you are taking 36 thread pitch out of .035 wall and having no trouble. I hadn’t really thought about it but I guess even the threaded areas still provide strength against expansion even though the material thickness is cut down in the valleys. I was basically using the unthreaded thickness that was left as my thickness and not counting the thread depth in terms of strength.

I am planning on the tube OD shrinking down in between the threads, but I still want to keep the larger O.D. as small as possible since 1.5” is really a little big for my brand new Trijicon suppressor height sights☹️...... which I think are one of the tallest options without going to a red dot sight.

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