How does this .223 design look?

Tanasoo · Post by **Tanasoo** » Tue Nov 03, 2009 3:34 pm

I was hoping to get your opinions on this design.

I'm wondering if I should remove a baffle and have a bigger blast chamber, or make it longer or, leave it the way it is?

OAL is 6.4" not including the part sticking out to thread onto the barrel. OD is 1.5" and ID is 1.37. Bore size is .29" and the end cap has a .302 hole.

I'm I want to have this screw together, but I'm worried that the wall would be too thin @1.5 OD. Should I be? Thread is 1 7/16 -18 UNEF.

Thanks!

dvanncvann · Post by **dvanncvann** » Tue Nov 03, 2009 4:02 pm

I would add 1"-1.5" to the blast chamber.

Tanasoo · Post by **Tanasoo** » Tue Nov 03, 2009 6:21 pm

Yeah, that's kind of what I was thinking.

Would it be worth the extra length to make the tube longer, or should I just remove a baffle and make a longer spacer?

dvanncvann · Post by **dvanncvann** » Tue Nov 03, 2009 8:08 pm

Make the tube longer.

Golf_1911 · Post by **Golf_1911** » Tue Nov 03, 2009 10:30 pm

I think make the tube longer by increase the lenght of Blast Chamber.

eagle106 · Post by **eagle106** » Wed Nov 04, 2009 2:42 pm

Depends. Is weight and length a factor? Such as, are you putting it on an AR-15 where you'll do a lot of moving and shooting or on a bolt action where you'll be using a bipod or benchrest?

Tanasoo · Post by **Tanasoo** » Wed Nov 04, 2009 5:11 pm

Length isn't really an issue. It will be threading onto a AR barrel.

Thanks for the input.

What do you guys think about the threads? They will be going into an .065 wall so that seems kind of thin. I really want to keep it at 1.5" OD, but I'll obviously have to make it larger if I have to... Maybe have steps over the threads? It still kind of defeats the purpose of having it 1.5" though.

bakerjw · Post by **bakerjw** » Wed Nov 04, 2009 7:54 pm

I'd go .085 if it were me.
Bigger blast chamber.
I'd also look into K baffles over the M/cone as shown but that's just me.
You may get rid of the spacers and add more of the M baffles too.

JohnnyO · Post by **JohnnyO** » Wed Nov 04, 2009 11:20 pm

Don't make the threads so corse, more like 32 tpi.
Other then that as well as a little larger expansion camber and I'd say is a good design for .223

dardani · Post by **dardani** » Thu Nov 05, 2009 4:49 am

remove first one or two baffles and it's ok .

Wicked · Post by **Wicked** » Thu Nov 05, 2009 6:08 am

From the info I've gathered here on this forum, the general rule (if there is such a thing) seems to be that the blast chamber should be approx. 1/3 or greater the volume of the can. Do you want to keep the same dimensions? If so, then removing the 2 M baffles closest to the muzzle and replacing them with 1 flat blast baffle up close to baffle #3 should get you a blast chamber that's about the right proportions.

SigOwner · Post by **SigOwner** » Thu Nov 05, 2009 6:22 am

A couple suggestions. I would thread internal for the muzzle attachment. The extension that sticks out the back of the can for threading onto the muzzle is just adding extra length to the setup (wasting space).

Also, Instead of the small "ring" like space that are between the baffles, why don't you just make the baffles with that incorporated into the design? Extend the outer tube part of the M baffle out to get the spacing that you want.

Tanasoo · Post by **Tanasoo** » Thu Nov 05, 2009 12:57 pm

The rings are there because it makes fabricating easier. And then I can mess around with some of the arrangement.

The threads for the muzzle were on the outside because I wanted to maximize the chamber size. Now that I'm making it longer I may go with making them internal... I also may make it go back over the barrel... Hmmm... The thing is I want to keep this one simple.

Tanasoo · Post by **Tanasoo** » Fri Nov 06, 2009 2:27 pm

Interesting... I have been working with the flow simulator is Solidworks. I tried extending the tube by one inch and ran the simulation, and it seems to make the first two baffles almost do nothing. The gas seems to just pass through the bore on them and only really gets disturbed at the third one. With the shorter design, it started to get disturbed at the second one.

I also added a simple flat "washer" baffle to the blast chamber to see if I could disturb the flow. It didn't seem to do much. I still need to put some holes in the washer so it doesn't get blown out.

I'm beginning to question the use of the flow simulator for this use. I think the required parameters are a little too specific for this tool. Right now I have it setup so the pressure on the muzzle side is around 20Ksi, and the end of the can is ambient sea level. The gas temp is around 1000 degrees F.

Does anyone have a better idea for these values? They were just my best guess off the top of my head to get the simulation running.

It seems to me like the simulation isn't accounting for the gas coming out of the barrel expanding into the lower pressure blast chamber, and that would make use of the first baffles. And of course there is the absence of the bullet, I'd imagine that when it first comes out of the barrel the gas would fan out around it rather than continue to follow the path of the bullet exactly. I wonder if there is a way to simulate the bullet moving through the baffles...

I'm probably thinking a little too hard on my "simple suppressor" but I thought you would find this interesting...

jjgow · Post by **jjgow** » Fri Nov 06, 2009 3:21 pm

You won't be able to accurately model the expanding gas from a gunshot with any software you'll be able to get your hands on.

Tanasoo · Post by **Tanasoo** » Fri Nov 06, 2009 3:38 pm

Well, I already figured that... I'm just posting my findings with the flow express simulator. It is interesting to say the least...

Mousehouse · Post by **Mousehouse** » Fri Nov 06, 2009 3:52 pm

Has anyone ever used a flow bench to check air/gas flow through a suppressor? The only problem is making the adapter.

Just curious.

Tanasoo · Post by **Tanasoo** » Fri Nov 06, 2009 4:51 pm

That would actually be very interesting... Especially if you had a clear outer tube, like a clear mock up so you could use smoke or particles.

The problem is suppressors are for bursts of gas, not constant flow. That's probably the biggest problem with flow simulating programs. We are talking about taking a sudden burst of high pressure gas and injecting it into a relatively low pressure chamber. If you have constant flow, the pressure on the inside of the can will probably equalize, and the flow would be different from when the can was in a low pressure state.

Well, I can theorize about this all day long... What do you all think about a flat washer baffle in the blast chamber with holes in it? I'm thinking to cause turbulence while still utilizing the volume of the blast chamber.

Tanasoo · Post by **Tanasoo** » Fri Nov 06, 2009 7:22 pm

Pretty much what I guessed would happen... That tells me that the baffles will indeed be doing something, but I'm still on the fence about the blast washer and it's placement. I'm thinking about in the middle? (right now it is 1/4 of an inch from the cap)

Todhunter · Post by **Todhunter** » Mon Nov 09, 2009 7:49 am

Tanasoo wrote:Interesting... I have been working with the flow simulator is Solidworks. I tried extending the tube by one inch and ran the simulation, and it seems to make the first two baffles almost do nothing. The gas seems to just pass through the bore on them and only really gets disturbed at the third one. With the shorter design, it started to get disturbed at the second one.

I also added a simple flat "washer" baffle to the blast chamber to see if I could disturb the flow. It didn't seem to do much. I still need to put some holes in the washer so it doesn't get blown out.

I'm beginning to question the use of the flow simulator for this use. I think the required parameters are a little too specific for this tool. Right now I have it setup so the pressure on the muzzle side is around 20Ksi, and the end of the can is ambient sea level. The gas temp is around 1000 degrees F.

Does anyone have a better idea for these values? They were just my best guess off the top of my head to get the simulation running.

http://img196.imageshack.us/img196/1897/short1z.jpg
http://img43.imageshack.us/img43/1586/long1s.jpg
http://img21.imageshack.us/img21/8093/longblast1.jpg

It seems to me like the simulation isn't accounting for the gas coming out of the barrel expanding into the lower pressure blast chamber, and that would make use of the first baffles. And of course there is the absence of the bullet, I'd imagine that when it first comes out of the barrel the gas would fan out around it rather than continue to follow the path of the bullet exactly. I wonder if there is a way to simulate the bullet moving through the baffles...

I'm probably thinking a little too hard on my "simple suppressor" but I thought you would find this interesting...

Try modeling it with just inside the muzzle @ 20KSI and just outside the muzzle @ ambient. The entire can is at nearly ambient pressure the instant the gasses enter. Also, to properly model this with the software you are using, you will probably have to do it in steps, one step per baffle. The bullet blocks most of the gas flow into the next chamber as it passes through a baffle. As someone said before, this is more of an impulse calculation, not steady state.

mactool · Post by **mactool** » Mon Nov 09, 2009 10:45 am

you havent taken into account the deflection there is from the base of the bullet.
I would put a plug in fron of the barrel, and then move that plug in increment of 0.5" all the way though the model. that way you have a better guesstimate

LavaRed · Post by **LavaRed** » Mon Nov 09, 2009 10:58 am

There is, however, also a suction effect created by the base of the bullet, sucking gasses into the bullet path, that needs to be taken into account.

The problem deepens.

Tanasoo · Post by **Tanasoo** » Tue Nov 10, 2009 2:18 am

I haven't had much time to do testing in the last few days (it locks up the computer for about 10-15 minutes while it is solving, if I try to do much else, it will run out of memory

)But I did do a couple of tests that I haven't posted.

ETA: Oh, I guess I did post my results with the bullet... Silly me. I guess I did take into account the base of the bullet

I modeled myself up a 55 gr FMJBT off the reloading bench (I'm going to do do a pulled 855 next just for chuckles and grins) and put it into the assembly to do some simulations. I also modified the barrel end plug to more closely represent the end of the barrel, including the crown.

The first test I did had the bullet about an inch from the barrel. The simulation showed almost no change in the flow, with the exception of the gas moving around and conforming to the bullet. keep in mind that the simulation has the bullet stationary. I am not sure if the bullet or the gas is moving quicker at this point.

The second one, I had the back of the bullet about .001 from the front face of the barrel. This one I believe is one of the more useful ones, because even though the program assumes a stationary scene, it is still close to what is happening in the real world. Predictably right at the gap between the bullet and the barrel, the gas was jetting out in all directions, and interacting nicely with the blast chamber and the first baffles.

So even though if I was blowing 20Ksi air through the can, it wouldn't have much effect from the first two baffles, if I was actually firing the bullet through it they would be useful.

The way this simulation is setup I need to plug each end of the suppressor in order for solidworks to know the volume. I then select a face for the entrance and exit and specify conditions for both. To my knowledge there is no way to specify the pressure for the internal volume because the simulation is meant for constant flow.

Ideally the program would be able to calculate and replay in short time intervals a burst of high pressure gas; and take into account the movement of the projectile, compression, and decompression of the gas, and supersonic flow. I'm sure there are also many other factors that a more physics tuned mind would think of.

After the first one or two simulations it was clear to me that it would not be even close to an accurate (complete) model of what is actually happening, it has still been interesting and enlightening to experiment with. I also think it would be very useful on a component level when it comes down to tweaking geometry for specific needs.

... It would also be handy for designing VLD bullets, but that's a whole other art that I don't have time for... yet...