I'm getting desperate!

[Fudmottin]

Sort of. It turns out that SRT makes exactly what I'm going for:

http://www.srtarms.com/mkii.htm

I want to avoid using packing. That stuff fouls up too quickly. Too much maintenance and it is so 1942. I haven't made a model of the design yet. What I am looking at doing is removing the front sight and turning down the barrel. The rear 3/4" and a section in the front will only be turned down to the ID of the main tube. The muzzle will get a 60 degree crown for spreading the gas into the blast chamber. The middle part of the barrel will be turned down to about 1/2" OD and get some ports.

This will constitute the rear chamber. In front of the muzzle it will look a lot like a standard muzzle can that is rather short. There will be a small blast chamber with blast baffle. Then a series of slant baffles followed by the end cap. I don't have a precise baffle count yet or precise location and size for the ports. I'm thinking about using an eight inch tube. If I go with a shorter tube, I will also shorten the barrel a bit.

The rear chamber will be sealed from the front chamber. So when gas goes through the ports, it has to go back through the ports to exit. Effectively this makes the barrel seem longer to the front part of the suppressor which is why it can be shorter than a typical muzzle can.

I'll use a chronograph to help size the ports. I'll shoot some rounds over the chronograph before porting to get a starting velocity. Then I'll start the ports. Then shoot over the chronograph again. I'll enlarge the ports as slots, making them longer each time I shoot over the chronograph until I start seeing the velocity go down. Somewhere between 5-10% I'll stop and that will be the size of the ports.

As for where I start the ports, it looks like from the data Artful pointed me too, I am safe starting about an inch from the muzzle and working backwards. Using slots will help me around the problem of gas making a 90 degree turn which is something it doesn't like to do.

I'll document the process so that however it works out, F1 can makers will know if they want to imitate that design or go in some other direction. The design is rather simple and you can be sure that I'm not sure if it will work or not.

Before I commit to cutting a perfectly good MKII barrel, I plan on making a short muzzle can out of delrin for a Marlin with 22" barrel to make sure that the front portion of the integral will work. It should be simple enough to make a throw away can out of delrin and I will also get an idea about how many baffles I actually need and what sort of length is really required to do the job.

The volume of a 22" barrel is a bit under a cubic inch. Obviously a 5 1/2" barrel (which will get shortened slightly by the crowning) is somewhat less. The porting in the integral simulates a longer barrel except the work of pushing a bullet through the longer barrel hasn't been done. So the muzzle gas in the integral is still going to have more energy than the muzzle gas from a rifle length barrel.

The reason barrels get ported and shortened in integral designs is not to slow down the bullet but to allow more volume for the can in a given length. Slowing down a bullet that is already subsonic anyway doesn't do anything for suppression. It's the gas that needs to be slowed down. The exception to this is when bullets go into the transonic velocity range (starts at about 1089fps depending on conditions). The bullet flight noise starts to get a lot louder with each foot per second until it is fully supersonic. At that point, the bullet flight noise is constant and quite loud.

Preserving most of the muzzle velocity allows one to choose a load based on noise and velocity. Remington Subsonic ammo is good for quiet shooting. Standard velocity will only be a little louder and you shoot a heavier bullet. High velocity will go even further with more energy but risks the ballistic crack.

[pug]

I am going to assume if you live in the US you know the laws regarding making even a single suppressor baffle.

Pressure, velocity and SPL are all interrelated so porting effects all three. Most integrals will not cycle shooting subsonic ammunition. The Amphibian would hardly cycle shooting HV rounds until broke in or at least that is what was reported when it was first released.

If you are looking for good suppressor reference material, Alan Paulson's book, Silencers:History and Performance is excellent and the $35 is well spent. It does not have design details on some of the newer baffles like the "K" but it does have info on some asymetrical designs and the overall info on suppressors is invaluable. Good luck with your design and happy shooting.

[Fudmottin]

Absolutely! This project will not begin without getting the Form-1 tax stamp back. All NFA + GCA rules will be followed.

I've got volume one of Al Paulson's book and will be ordering volume 2. I can't wait for volume 3 to actually come out. It seems Al Paulson must be a fan of DEK (inside joke. If you don't get it, don't worry). Anyway, Vol 1 has been a good read so far. I recommended it to certain government officials who allegedly represent me in PA and USA house and senate.

The SRT does not have the problems of the Amphibian. In fact, if I hadn't gone blowing all sorts of money on silly things like metal working tools (hobby grade), I would have Doug fix me up. I'm sure his is better than mine. But I'm equally sure that mine is better than AWC's. I would actually have SRT fix me up anyway except that I do have a rather healthy level of intellectual curiosity about the entire subject of suppressor design. The subject is quite fascinating on every level.

BTW, I use the same nick on Silencer Talk as I do here and some other internet places. I don't want HOMSEC having any problems tracking me ;-)

Since you are familiar with Paulson's work, you will also be familiar with Mark White. I am following the guidelines laid out in Patent 7,073,426 for my design. That will be for the portion ahead of the muzzle obviously. The reasons are simplicity of design and manufacture. I could certainly make Ks. I am familiar with several different variations on the K baffle. However, they require more labor than simple slant baffles.

I'm aware that YHM's Mite did not rate well on Silencer Research. I suspect there are a couple reasons for that. One is the lack of the symmetrical blast baffle with diffusion holes near the periphery. The other has to do with the baffles being too close together for the gas jet to be deflected enough to miss the bore hole.

I could be wrong of course.

My engineering education is from an entirely different background. And as such, I can't help but see that there seems to be a lot of "ad hoc" design work. Even the MIL standard is unscientific. They are fine with the type of microphone, placement, and calibration. But then they go and do the test outdoors over grass. That is not reproducible. You need a much more controlled environment than that.

Also people seem to be guessing at how the gases actually flow in a stochastic system.

The state of the art is what it is. I wish I had time to pursue all my interests. Given time and resources, I could probably accurately model real gas flows in a suppressor. Although the way I write code, a serious amount of CPU, memory, and bus bandwidth resources would be required. I think the NSA has what I need. LANL probably does too.

Thanks for the well wishes. I know I am a complete amateur in this. It will take some tenacity and time to achieve professional level results. I think Form-1 cans only save you money when you already have the tools and knowledge of using them. Add to that other issues such as finite element analysis to know how strong things need to be and how to make them just that strong and computational fluid dynamics to get you to a real world prototype for testing which also requires some rather pricey equipment.

[querty]

Can anyone please tell me which type of Ruger Mk2 is the best platform to
create an integral from? I live in France and info on Rugers is rare here.
I notice that companies in the US that do conversions on Mk11`s seem to
charge less for ones with a bull barrell! why is that? I`m an engineer and
plan to build my own integral. When I`ve finished it I`ll post the the results
on the site including MV and sound reduction (I`m also a sound engineer)
done above grass, which is perfect due to Sabine loss! I would much appreciate
use of you experts out there on the Ruger.

[Hoser]

Why not just run a 4 inch barrel and thread on a same OD can and polish it to a perfect finish where you cant see the seam.

You start putting holes/ports in the barrel and accuracy *will* suffer. My JET intergal can on my 10/22 is quiet, but not that accurate with any ammo.