How about another 50 BMG build

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.

Moderators: mpallett, bakerjw

Post Reply
mdfoster
Member
Posts: 24
Joined: Thu May 11, 2006 6:02 pm
Location: NC

How about another 50 BMG build

Post by mdfoster »

I just got a M99 and after seeing the other 50 builds over the past few years I got jealous. I haven't done a form 1 build yet, but have been planning various designs for a while. I have a 12x36 lathe that is in storage from my recent move, but I should be able to get it set up by the time my approved form gets back. I have no tig skills, but plan on working on that in the meantime. As far as the design right now I am thinking:

2.5"x18" 4130 grade tube
6" blast chamber
flat blast baffle with scoop
(6) 60 degree conical baffles turned from 4130 grade SR. The first 4 would be clipped.
Image


Any helpful comment would be appreciated.

ETA
Does anyone know what the muzzle threads are on a M99?
AAC 7.62SD
SWR Warlock
User avatar
Bendersquint
Industry Professional
Posts: 11357
Joined: Sat Jan 07, 2006 7:19 pm
Location: North Carolina
Contact:

Re: How about another 50 BMG build

Post by Bendersquint »

mdfoster wrote: Does anyone know what the muzzle threads are on a M99?
Depends on when the M99 was made, old ones had 3/4-20 and newer ones have 3/4-24. You can call Barrett and they will tell you what you have if you haven't/can't gage the threads yourself.
mordamer
New Member
Posts: 2
Joined: Sun Aug 14, 2016 9:08 pm

Re: How about another 50 BMG build

Post by mordamer »

A word of caution on the threading on the Barret M99. I recently measured one that was 3/4-20 muzzle threads and found that the threads did not appear to be cut to a specific thread spec. I am trying to recall what the pitch diameter and major diameter were but I remember them being way off from what I was expecting from a 3A thread. I used thread wires for my measuring and checked several times. If you are making a mount or end cap to go on an M99 I would highly recommend measuring the threads on the specific gun instead of threading to a spec.
User avatar
whiterussian1974
Silent But Deadly
Posts: 2857
Joined: Sat Sep 28, 2013 11:37 pm
Location: On 8th line of eye chart.

Re: How about another 50 BMG build

Post by whiterussian1974 »

No one else has mentioned your design, so I will.

1- That's a lot of unharnessed blast chamber. You could add a couple of cones just in there. Unless you're intending to use a muzzlebrake, there aren't any obstructions to redirect the gas jet off of Boreline.

2- Instead of scooping the 1st baffle, and the next 4 cones; you should leave the 1st baffle symmetrical, then clip or notch the LAST few baffles. This will aid in keeping better accuracy and increase turbulence at lower pressure.

3- Unless this is a reflex build (you don't show it to be), you are leaving a lot of underutilized space inside the tube. Add more cones. Including near the far endcap. Even if you need to flatten the cone from 60* to 45*. This will act as a transition before the 0* endcap. Thus trapping more low pressure gas as it expands outward.

4- You could also add a coaxial sleeve inside of the blast chamber. This would add quenching surface and help to delay some of the gas before it returns to the boreline. Just a simple smaller diameter sleeve w many holes or slits bored into it. Many designs feature this. (But not all.)

You've got a solid start. Just these few mods should increase your performance.

Have you checked the "links to completed builds" thread? Lots of great design elements on display there. :D viewtopic.php?t=79895

Here are some links to other .408/.50 builds:
viewtopic.php?f=10&t=62370
viewtopic.php?f=10&t=34412
And a .300WM w similar design: viewtopic.php?f=10&t=78425

F1 .50 can: viewtopic.php?f=10&t=20992&start=25
Image
Image
The Darkest Corners of Hell are reserved for those who remain Neutral!-Dante
The Death of One is a Tragedy, a million only a statistic.-Stalin
silencertalk.com/forum/viewtopic.php?f=10&t=135314
User avatar
Bendersquint
Industry Professional
Posts: 11357
Joined: Sat Jan 07, 2006 7:19 pm
Location: North Carolina
Contact:

Re: How about another 50 BMG build

Post by Bendersquint »

whiterussian1974 wrote:No one else has mentioned your design, so I will.
1- That's a lot of unharnessed blast chamber. You could add a couple of cones just in there. Unless you're intending to use a muzzlebrake, there aren't any obstructions to redirect the gas jet off of Boreline.
2- Instead of scooping the 1st baffle, and the next 4 cones; you should leave the 1st baffle symmetrical, then clip or notch the LAST few baffles. This will aid in keeping better accuracy and increase turbulence at lower pressure.
3- Unless this is a reflex build (you don't show it to be), you are leaving a lot of underutilized space inside the tube. Add more cones. Including near the far endcap. Even if you need to flatten the cone from 60* to 45*. This will act as a transition before the 0* endcap. Thus trapping more low pressure gas as it expands outward.
4- You could also add a coaxial sleeve inside of the blast chamber. This would add quenching surface and help to delay some of the gas before it returns to the boreline. Just a simple smaller diameter sleeve w many holes or slits bored into it. Many designs feature this. (But not all.)
1 - Blast chamber is about the right size for a 50BMG.

2 - There is no need to add turbulence at lower pressure because there is no lower pressure with a 50BMG can. I would leave the first baffle without a feature on it however I wouldn't use a flat plate but a cone of some sort. I would clip/notch(whatever you want to call it) ALL of the baffles after the blast baffle.

3 - Cone number is about right, I might add maybe 2 but thats it. Stick with 60 degree cones as well. Endcap design is fine for the sketch he has drawn up.

4 - Not sure what a quenching surface is but on a 50 you won't get alot of benefit from a coaxial blast chamber and there is a distinct possibility that it would hurt performance more than help.
User avatar
whiterussian1974
Silent But Deadly
Posts: 2857
Joined: Sat Sep 28, 2013 11:37 pm
Location: On 8th line of eye chart.

Re: How about another 50 BMG build

Post by whiterussian1974 »

Thank you for Refining my Advice Bender. :) :idea:

You are the Pro. I'm just a Theorist. With little Experience to boot. :shock:

Why wouldn't you alter the Blast Chamber except to change baffle from Flat to Cone? Quenching Surface is added thermal absorption area. The perforated sleeves in the Xray pic. Units 1, 2, 4, 5 show them clearly.

I wasn't sure if they would help much w .50 because of the MASSIVE gas Volume. But thought that added thermal surface area would help quench remaining burning propellant and lower initial Muzzle blast temp. USAF "hush houses" use this design to dampen Afterburner sound energy. The perforations also add their own physical sonic properties. There are many actions that the ports perform. Like a cheese grater/exhaust Diffuser, or egg carton foam in a Recording studio. I use it on my front room windows to absorb sound from Traffic/Stereos.
The Darkest Corners of Hell are reserved for those who remain Neutral!-Dante
The Death of One is a Tragedy, a million only a statistic.-Stalin
silencertalk.com/forum/viewtopic.php?f=10&t=135314
User avatar
whiterussian1974
Silent But Deadly
Posts: 2857
Joined: Sat Sep 28, 2013 11:37 pm
Location: On 8th line of eye chart.

Re: How about another 50 BMG build

Post by whiterussian1974 »

Bender: Would this be a good design for .50BMG?

It MAY be overbuilt for such high gas volume. But it sure is sweet!

I'd ALWAYS prefer a 24"L over 18". Reflex helps add volume w/o adding barrel Length.

I'd change the Muzzle attachment though. Use the muzzle brake as a coaxial perforated sleeve that blows backward into the Reflex section. A quasi-baffle that segments the Reflex from the Blast chamber in front of the break. Forcing the Reflex to vent back through the Break to reenter Boreline in order to transit the Break b/f moving forward into the Baffle Stack.
Image
The Darkest Corners of Hell are reserved for those who remain Neutral!-Dante
The Death of One is a Tragedy, a million only a statistic.-Stalin
silencertalk.com/forum/viewtopic.php?f=10&t=135314
mdfoster
Member
Posts: 24
Joined: Thu May 11, 2006 6:02 pm
Location: NC

Re: How about another 50 BMG build

Post by mdfoster »

I do like the look of that reflex chamber. I also have an omega baffle design similar to the one shown. I just figured it would be more difficult to make work and cones are fairly proven.
AAC 7.62SD
SWR Warlock
User avatar
whiterussian1974
Silent But Deadly
Posts: 2857
Joined: Sat Sep 28, 2013 11:37 pm
Location: On 8th line of eye chart.

Re: How about another 50 BMG build

Post by whiterussian1974 »

Here's MY SDTA-modeled .50BMG can. It was actually designed for .308-.300WSM, but option of up boring to .375CheyTac at 7/16" (.4375"), and could be upscaled for .50s @ 9/16" (.5625"). Simply lengthen to 18-24". 2" behind Muzzle, 2" around Break, 14-20" of cones in front of the Blast Baffle. :idea:

Just don't use the EDM barrel slits. Instead, move those 2" forward and use the Reflex volume to absorb the blast from the muzzle brake. Otherwise, it works great for a larger caliber. :D

Also notice my fluted endcap ports. Gunny50 uses them in his Commercial builds in EU. So it works. :wink: :mrgreen:
viewtopic.php?f=10&t=135314&hilit=SDTA
Image
Gunny50s ported endcap:
Image
T-Rex's design draft:
Image
Just some added options. 8) :mrgreen:

I agree that Omegas aren't best for .50s. The links that I posted used "step/Aztec" baffles. (Some use Ti Valve spring retainers for ease of adaption.) Many say that those only benefit "integrals." I think that it "might" be good for the 1st Baffle, but regular simple 60* cones for the rest. The added weight and complexity aren't worth any effort for hopes of performance enhancement. :idea:
The Darkest Corners of Hell are reserved for those who remain Neutral!-Dante
The Death of One is a Tragedy, a million only a statistic.-Stalin
silencertalk.com/forum/viewtopic.php?f=10&t=135314
User avatar
jimmym40a2
Elite Member
Posts: 2745
Joined: Sun May 06, 2007 8:25 pm
Location: Colorado (for Mongo)

Re: How about another 50 BMG build

Post by jimmym40a2 »

dont get two complicated. Mine is super simple and is very quiet.
http://www.youtube.com/watch?v=nEZJ_C4LwzA
Post Reply