30 Cal Form 1 Project

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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Matt in TN
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30 Cal Form 1 Project

Post by Matt in TN » Sun Oct 20, 2019 9:04 pm

With a lot of help and advice from many here, I just finished my second form 1. This was primarily for 300BLK subs, but I wanted it to do OK with supers and .308 as well. Titanium tube and spacers came from Diversified Machine. End caps and baffles were made from 17-4 and a little 416 (when I ran out of 17-4!). Final specs are 1.625" OD x 8" long, and it weighs in at 21 ounces.

Rear End Cap came first - this was cutting wrench flats with a spin index on the mill:
Image

Then cutting the internal cone shape from 17-4A bar stock:
Image

And the external cone shape:
Image

Alignment notches in the cones (the 3 rings are to remind me these are 416 and need to be in the front):
Image

Clipping the cones:
Image
Last edited by Matt in TN on Sun Oct 20, 2019 9:11 pm, edited 1 time in total.

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Sun Oct 20, 2019 9:08 pm

Cutting alignment tabs in the titanium spacers:
Image

Here's everything but the front end cap:
Image

Cutting kidney-shaped relief cuts in the inside of the front end cap with a rotary table:
Image

Front end cap, baffle stack (after testing) and tube:
Image

Finished with Gunkote, mounted on an 8.5" barrel 300BLK:
Image

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Sun Oct 20, 2019 9:10 pm

And here's the test video. No fancy mics or cameras - just a simple iPhone and iPad. But hopefully it gives you an idea of the sound. It has more FRP than I'd like, but I think that was necessary to make the blast chamber big enough to handle supers and .308 as well. Everything is a trade-off. Overall I'm happy, and I learned a LOT along the way!

https://youtu.be/q-Df4_Mtd90

Historian
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Re: 30 Cal Form 1 Project

Post by Historian » Mon Oct 21, 2019 9:05 am

Matt,
Masterful presentation.
Enviable workmanship.
You are most generous to show and
brighten the morning for 'metal-mania-men"

But, pray tell, what is the 'Jerry Nadler' gnome doing
next to your great work of art? :) :)

Best

p.s., in an obscure 1960s can design a hollow 'jelly-roll'
of bronze wrap screen was fit into the blast baffle, like
a cigarette filter with hole of course in center,
made of an interleaving of coarse copper (e.g., chore girl (?) )
First round pop was ameliorated.

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Mon Oct 21, 2019 10:18 am

Thank you, sir! That little gnome made his first appearance at a "Run N Gun" we put on for the 5th Special Forces Group a couple years ago. You ran 3.2 miles through the woods while carrying your rifle, pistol, and all your ammo - stopping to shoot 5 different stages along the way. The gnome was standing in the middle of the trail at the farthest point out, way back in the woods, with no explanation.

At the final stage the shooter was told their target was inside a building with a door the same color as the hat of the gnome they met along the trail. All of the SF guys made note of this "thing" out of place and got the hint. Most of the civilians that shot the match did not, and had to clear three different buildings to find their target.

So now this little guy shows up in all sorts of odd places as an inside joke. I'm a little guy myself, and this is a little rifle - so it kinda fits.

That's a great point about the screen. I wonder if I could figure a way to put some copper wool in the blast chamber and get it to stay out of the bore line...

rickiesrevenge
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Re: 30 Cal Form 1 Project

Post by rickiesrevenge » Mon Oct 21, 2019 7:02 pm

I'm new here and have a couple questions. What does the clipping on the cone do? Any reason you have spacers instead of having them as part of the cone?

Aaron

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Mon Oct 21, 2019 11:35 pm

Spacers were easier to make/buy separately, lighter (titanium spacers were thin and cheap), and took less material overall. Cutting them as part of the cone would have made for a simpler assembly and probably better in the end, but I went with "easier to machine" as it's a centerfire can and I don't plan on taking it apart much if any.

Clipping the cone makes the gas flow assymetrically, which increases turbulence, slows the gas, and increases suppression. But it also made all the alignment notches and tabs necessary to keep them all lined up (alternating one side to the other). Theoretically if all the clips are on the same side suppression will be maximized, but so will POI shift. By alternating the clips for every cone and keeping them the same shot to shot it should minimize POI shift and still get reasonably good suppression.

I THINK (I'm new too!) that the clipped cones do more for supersonic rounds and not much at all for subsonic rounds. And that fewer cones with greater spacing would have done better for supersonic rounds, but not as well for subsonic. So I split the difference and did clipped cones with close spacing as a compromise. Hopefully it was a reasonable compromise and didn't just make both things worse!

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Re: 30 Cal Form 1 Project

Post by ECCO Machine » Tue Oct 22, 2019 11:10 am

Looks good. Hope the crescent clips work out for you, I did not have good luck with them in subsonic or supersonic applications across multiple calibers.

I would strongly recommend heat treating your parts, especially the 416 bits. In the annealed state, 416 is softer & weaker than 304.
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Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Tue Oct 22, 2019 11:29 am

ECCO Machine wrote:
Tue Oct 22, 2019 11:10 am
Looks good. Hope the crescent clips work out for you, I did not have good luck with them in subsonic or supersonic applications across multiple calibers.

I would strongly recommend heat treating your parts, especially the 416 bits. In the annealed state, 416 is softer & weaker than 304.
Dangit, man! And then CaptLink (I think?) [edit - it was curtistactical, see below post and quote] said he tested these clips against u-shaped clips and found that these were 5dB quieter, and both were significantly quieter than no clips (going off memory here). There's never just one answer!

Good info on the heat treat. I'm hopeful putting the few 416 baffles at the muzzle will help minimize any issues. And I probably should find a local heat treat place.
Last edited by Matt in TN on Tue Oct 22, 2019 10:10 pm, edited 1 time in total.

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Re: 30 Cal Form 1 Project

Post by Capt. Link. » Tue Oct 22, 2019 5:44 pm

416 must be heated to a cherry red to prevent annoying surface rust.This basic heating can be done on the stove top w/ no need for quenching.A full heat treatment would be even better! I love using it because it cuts so nice!

I'm a asymmetric baffle devotee, but would switch if a simple port in a cone yielded a whopping 5db performance increase. I would follow ECCO's advice on "clipping" as he has more experience with cone baffles then I.

Nice work looking for a field report.
The only reason after 243 years the government now wants to disarm you is they intend to do something you would shoot them for!

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Tue Oct 22, 2019 8:21 pm

Capt. Link. wrote:
Tue Oct 22, 2019 5:44 pm
416 must be heated to a cherry red to prevent annoying surface rust.This basic heating can be done on the stove top w/ no need for quenching.A full heat treatment would be even better! I love using it because it cuts so nice!

I'm a asymmetric baffle devotee, but would switch if a simple port in a cone yielded a whopping 5db performance increase. I would follow ECCO's advice on "clipping" as he has more experience with cone baffles then I.

Nice work looking for a field report.
If not you, then who? I'm going to have to dig this out now. It was a well respected member...

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Re: 30 Cal Form 1 Project

Post by ECCO Machine » Tue Oct 22, 2019 9:08 pm

Matt in TN wrote:
Tue Oct 22, 2019 11:29 am
Dangit, man! And then CaptLink (I think?) said he tested these clips against u-shaped clips and found that these were 5dB quieter, and both were significantly quieter than no clips (going off memory here). There's never just one answer!
No, there's not. Lol. But I've played with a lot of different styles, many variation on geometry with each. Single radiused clips of ~1/2 aperture diameter and slightly deeper than they are wide work well for high velocity, high pressure applications, and double radiused clips closer to 35-40% of aperture diameter for subsonic/low pressure stuff. And alignment makes a big difference in suppression, and often with POI shift in the case of single clips.
Matt in TN wrote:
Tue Oct 22, 2019 11:29 am
Good info on the heat treat. I'm hopeful putting the few 416 baffles at the muzzle will help minimize any issues. And I probably should find a local heat treat place.
Most places are gonna charge you about $100/batch for quench & temper, whether that batch is the maximum batch size or a single small part.

If you have an acetylene torch you can do it yourself, heat them as slowly as possible to a medium orange and then air or oil quench. That won't be as good as a proper, accurate 1,800°F soak, of course, but it will harden them. You can temper in your kitchen oven, basically as hot as it can go on bake, usually about 550°F. Do not use the clean cycle, though; that's generally 850-900°, and that's a range you do not want to temper 416 at. Would work for your 17-4, though!

http://www.crucible.com/PDFs/DataSheets ... 20plus.pdf
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Re: 30 Cal Form 1 Project

Post by Capt. Link. » Tue Oct 22, 2019 9:59 pm

I would line up all the clips......You might benefit from base porting of the cones as well.I would also try to move the core towards the muzzle to tune!
Have you tried heavy subsonics : 230gr SMK @ 900-950fps accurate,powerful,quiet.
The only reason after 243 years the government now wants to disarm you is they intend to do something you would shoot them for!

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Tue Oct 22, 2019 10:09 pm

My bad - it was curtistactical:

" I started with an all cone 30cal suppressor with no clips and 8 cone baffles, next I put the radius scoop in, lastly I cut them .125" deep to center of the bore. I tested this using 308 200gr subs and 308 175gr supers. With both loads the .125" to cl cut was around 5db quieter than the radius cut and both were dramatically quieter than unclipped. "

viewtopic.php?t=136662
Last edited by Matt in TN on Tue Oct 22, 2019 11:02 pm, edited 1 time in total.

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Tue Oct 22, 2019 10:12 pm

Capt. Link. wrote:
Tue Oct 22, 2019 9:59 pm
I would line up all the clips......You might benefit from base porting of the cones as well.I would also try to move the core towards the muzzle to tune!
Have you tried heavy subsonics : 230gr SMK @ 900-950fps accurate,powerful,quiet.
That UMC load was a 230gr bullet, but I haven't started handloading for 300BLK yet. That's next.

I may try lining all the clips up just to see if I can tell a difference. Thanks for all the info on heat treat!

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Re: 30 Cal Form 1 Project

Post by ECCO Machine » Tue Oct 22, 2019 11:37 pm

Matt in TN wrote:
Tue Oct 22, 2019 10:09 pm
My bad - it was curtistactical:

" I started with an all cone 30cal suppressor with no clips and 8 cone baffles, next I put the radius scoop in, lastly I cut them .125" deep to center of the bore. I tested this using 308 200gr subs and 308 175gr supers. With both loads the .125" to cl cut was around 5db quieter than the radius cut and both were dramatically quieter than unclipped. "

viewtopic.php?t=136662
Here's the problem:
I don't have any photos of the scoop cut but it was done using a .312" ball nose end mill and taken .16" deep
Too wide, not deep enough. On a .370" aperture .30 cal size, I do .190" wide, .200"-.230" deep, depending on cone thickness. That's with my 50° cones

Image

This was a 5" .30 can I recored earlier this month:

Image

And here's what the owner had to say about it:

"Wish i had acess to a db meter, huge improvement actually sounds like my sandman s maybe a better tone"
FFL07/02SOT Gunsmith & Machinist

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John A.
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Re: 30 Cal Form 1 Project

Post by John A. » Wed Oct 23, 2019 9:48 am

Sorry that I'm just now seeing your build topic. You did a good job building that. You did some nice cutting with that.

The gnome is funny. I have a buddy who used to take pictures of an eric cartmann plush doll all over the place. When he went on vacations, laying on the pillow beside his wife while she was asleep :lol: :lol: :lol: :lol: .

In all sorts of weird places. It was all in good fun though. I don't think his wife appreciate it too much though :P
I don't care what your chart says

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Wed Oct 23, 2019 10:19 am

ECCO Machine wrote:
Tue Oct 22, 2019 11:37 pm
Matt in TN wrote:
Tue Oct 22, 2019 10:09 pm
My bad - it was curtistactical:

" I started with an all cone 30cal suppressor with no clips and 8 cone baffles, next I put the radius scoop in, lastly I cut them .125" deep to center of the bore. I tested this using 308 200gr subs and 308 175gr supers. With both loads the .125" to cl cut was around 5db quieter than the radius cut and both were dramatically quieter than unclipped. "

viewtopic.php?t=136662
Here's the problem:
I don't have any photos of the scoop cut but it was done using a .312" ball nose end mill and taken .16" deep
Too wide, not deep enough. On a .370" aperture .30 cal size, I do .190" wide, .200"-.230" deep, depending on cone thickness. That's with my 50° cones

Image

This was a 5" .30 can I recored earlier this month:

Image

And here's what the owner had to say about it:

"Wish i had acess to a db meter, huge improvement actually sounds like my sandman s maybe a better tone"
Have I mentioned how much I hate the fact that a Form 1 won't let you experiment? So many options and choices you just have to make and live with! ;-)

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Re: 30 Cal Form 1 Project

Post by Capt. Link. » Wed Oct 23, 2019 12:23 pm

I haven't heard from Curtis in the longest time hope he is well.I would still be surprised if a clip would yield 5 db but haven't the meter any longer to make measurements.

History of the NOME is much older than you may imagine.
I used to see them hiding in women's bras whenever it was cold outside,you could tell by their protruding nose's.
The only reason after 243 years the government now wants to disarm you is they intend to do something you would shoot them for!

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Re: 30 Cal Form 1 Project

Post by ECCO Machine » Wed Oct 23, 2019 2:39 pm

Capt. Link. wrote:
Wed Oct 23, 2019 12:23 pm
I haven't heard from Curtis in the longest time hope he is well.I would still be surprised if a clip would yield 5 db but haven't the meter any longer to make measurements.
While it made virtually no difference on rifles, I dropped 7 dB on Ocelot full size and 9 dB on Ocelot micro on handguns going from a crescent clip like Matt used to a double radiused clip. Same baffle count, same spacing. I did increase the cone size a bit as well, though.

Old style:

Image

New style:

Image

It was such a dramatic change that I scrapped all the baffles in the ones I had here and actually recored the few I'd sold at no charge.
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Re: 30 Cal Form 1 Project

Post by John A. » Wed Oct 23, 2019 3:30 pm

ecco, have you tried clipping at different heights or depths--however you look at it?

I mean one clip being 1/2 inch long from the face for instance an the other one being 3/8 of an inch long from the face just for example.

I'm just curious if that would change anything? I know it would the pressure, just not sure if it would change the db rating.
I don't care what your chart says

Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Wed Oct 23, 2019 5:59 pm

Capt. Link. wrote:
Tue Oct 22, 2019 9:59 pm
I would also try to move the core towards the muzzle to tune!
Not sure I understand what you're saying here. Do you mean cut the skirt on the front endcap down and add spacers between the rear end cap and rhe blast baffle to move the whole baffle stack forward? And how does that "tune" anything? Does it lower the pitch of the sound, or make some other change?

I thought I was done after two. But after all this mess about the cone clipping I'm tempted to make another!

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Re: 30 Cal Form 1 Project

Post by Capt. Link. » Wed Oct 23, 2019 6:50 pm

You might be able to lessen FRP and increase SPL losses with a reduction in blast chamber size ie: to tune the suppressor.You also might be able to create secondary expansion chambers through porting or the placement of spacer rings within the stack.
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Re: 30 Cal Form 1 Project

Post by ECCO Machine » Wed Oct 23, 2019 6:58 pm

John A. wrote:
Wed Oct 23, 2019 3:30 pm
ecco, have you tried clipping at different heights or depths--however you look at it?

I mean one clip being 1/2 inch long from the face for instance an the other one being 3/8 of an inch long from the face just for example.

I'm just curious if that would change anything? I know it would the pressure, just not sure if it would change the db rating.
A little bit, but not enough for any conclusive data. It's something I've been wanting to investigate further, just haven't had the time for R&D or personal stuff. Most of my replies on these boards are done in the 5-10 minute breaks I take through the day to give my feet a reprieve and let my hands dry so I can put on a new pair of nitrile glove! I have a number of ideas I want to try out, just not enough hours in the day to do it without sacrificing family time.
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Matt in TN
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Re: 30 Cal Form 1 Project

Post by Matt in TN » Thu Oct 24, 2019 9:35 am

ECCO Machine wrote:
Wed Oct 23, 2019 2:39 pm
Capt. Link. wrote:
Wed Oct 23, 2019 12:23 pm
I haven't heard from Curtis in the longest time hope he is well.I would still be surprised if a clip would yield 5 db but haven't the meter any longer to make measurements.
While it made virtually no difference on rifles,
Clipping at all made no difference on rifles, or changing from the crescent clip like I used to your new clip?

7dB is HUGE!!!

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