I'm getting desperate!

[Fudmottin]

I'm trying to design an integral suppressor for the MKII series pistol. I do not want to give up the velocity that the AWC Amphibian does. But I still want reasonable suppression.

I really need to know what the normal pressure and velocity curves are in a 22LR barrel.

I want to be able to have a chance at working out the barrel length to stick with and where the ports should be so that I do not lose too much muzzle velocity and still keep the muzzle pressure down for suppression.

Please help.

Thanks.

[LouBoyd]

You couild get a box each of several brands of ammo, then use a "sacraficial" barrel and crhonograph a a few shots from each box as you cut down the barrel in increments. A used barrel for a T/C doesn't cost a lot. That would give some useful data.

Quickload could do that only if you know the characteristcs of each powder and bullet used in each brand. You could also Use an Oehler chamber strain gage rig to get the pressure/time curves. You'd still have to make a lot of shots on different ammo unless you've already chosen what you're going to use.

What's so important about not giving up any velocity? Isn't it to be subsonic? You may want to give up velocity depending on the ammo you use.

[remhunter]

awc gives up only a little in velocity so u can shoot standard high velocity subsonic (which saves a lot of $ when buying ammo). I own one and love it. If you do not make it subsonic then it will still be loud from the sonic crack of the bullet which kind of defeats the purpose unless all you are trying to do is shoot it comfortably without ear plugs. Which I do with .22 calibers anyway.

[Fudmottin]

I'm trying to find a middle ground where I get the choice of velocity of using a muzzle can but the handier short length of an integral (not to mention the visual appeal of an integral). I would like the bolt to cycle on Remington Subsonic which I have a fair bit of. I don't think there is any 40gr loads that will go super sonic in a 5 1/2 inch barrel anyway, although I could be wrong.

If all goes according to plan, I would have a pistol that is maybe an inch or two longer than the Amphibian, a little louder, and a flatter trajectory.

The barrel porting location is rather important to final results. The Amphibian starts way back at the chamber (just about) and has the barrel much shortened. I want to be closer to the muzzle end with a longer barrel. The ports want to vent into a chamber so that as the bullet reaches the muzzle, it is still under just enough pressure to overcome bearing friction.

The portion of the suppressor ahead of the muzzle would resemble a shortened version of a traditional can.

Also the suppressor will be threaded for takedown. The Amphibian is sealed. I don't know how long it takes to lead up. But it will happen eventually. I expect that the location and size of the ports keeps them from accumulating lead for a while though.

A final word on velocity. The ideal is near 1000 fps. This keeps you shy of the transonic range so that bullet flight noise doesn't become a problem. It also gives you somewhat more "point blank range" than 800 fps will which is about the best the Amphibian will do with fairly hot ammunition. Going lighter than 40 gr just makes things worse because you lose ballistic coefficient.

[Artful]

Originally Posted by Fudmottin

I'm trying to find a middle ground where I get the choice of velocity of using a muzzle can but the handier short length of an integral (not to mention the visual appeal of an integral). I would like the bolt to cycle on Remington Subsonic which I have a fair bit of. I don't think there is any 40gr loads that will go super sonic in a 5 1/2 inch barrel anyway, although I could be wrong.

All the 40 high velocity go supersonic in my 5.5 ruger barrel, All so far tested in 4.5 High Standard barrel stay subsonic. If your just shooting Rem. Subsonic of course it doesn't matter.

Quick google shows some Velocity vs barrel length
http://plainsmanscabin.yuku.com/topic/4050
_______________BARREL
FIREARM________LENGTH______VELOCITY______AMMUNITIO N
(MAKE)_________(INCHES)_____(FPS)________(BRAND)
(Model)___________________ CCI_____CCI______CCI
________________________STANDARD MINIMAG STINGER
S&W317____________3_____843______923________1,13 8
S&W 34____________4_____872______980________ 1,154
Kimber 1911_________5_____910_____1,037_______ 1,264
S&W K-22__________6______897_____1,023_______1,232
S&W 41____________7______959_____1,125_______1,422
Remington 504_____20_____1,100_____1,266_______1,576
Remington 12-C____24_____1,005_____1,150_______1,506
COPYRIGHT 2005 Publishers' Development Corporation

http://www.kifaruforums.net/archive/...hp/t-6867.html
In the VOL. 9, NO. 4 issue of GUNS & AMMO magazine, Bob Milek wrote an article titled: BARREL LENGTH VS VELOCITY, where he took a number of barrels and guns and cut down the barrels in one inch increments, measuring the velocity loss at each step of the process for a number of centerfires as well as the 22LRs. It's a very interesting article. Here are the velocities recorded for the 22LR starting at 14 inches and going down to 4 inches.

14" = 1,105 fps.
13" = 1,106
12" = 1,110
11" = 1,089
10" = 1,114
..9" = 1,077
..8" = 1,063
..7" = 1,057
..6" = 1,024
..5" = ..959
..4" = ..927 fps.

http://www.boards.ie/vbulletin/showt...php?p=59873169
We used five CZ 452 .22 rifles with different barrel lengths and fired six rounds each of six different cartridge types. The chart below reflects the average velocity of the six rounds.

The rifles were:
CZ 452 Ultra Lux with a 28.6” barrel
CZ 452 Special with a 24.8” barrel
CZ 452 American with a 22.5” barrel
CZ 452 FS with a 20.7” barrel
CZ 452 Classic with a 16.5” barrel (Fuzzy the Limey’s old CMP Sporter rifle)

The cartridges were:
CB Longs = CB
RWS Subsonic Hollow Points = SSHP
Wolf Match Target = Standard Velocity or SV
American Eagle Solids = Lead High Velocity or LHV
CCI Mini Mag Solids = Plated High Velocity or PHV
CCI Stingers = Hyper Velocity or HypVel

-----CB SSHP SV --LHV -PHV HypVel
28.6 652 968 1037 1206 1188 1660

24.8 676 997 1062 1219 1217 1660

22.5 653 998 1069 1229 1213 1708

20.7 701 957 1062 1224 1190 1661

16.5 685 949 1057 1205 1208 1666

The following information is from Mark White's book "The Ultimate Ruger 10/22 Manual and User's Guide" . Apparently, he cut a 28 inch barrel two inches at a time and measured for muzzle velocity.

Ruger 77/22; Remington Standard Velocity .22 LR ammunition
Barrel Length/ Velocity
28 1095
26 1107
24 1119
22 1129
20 1138
18 1149
16 1157
14 1149

[Rikky Lee]

Change the action springs.

[Fudmottin]

I'm trying to do an delicate balancing act while juggling an axe, bowling ball, and egg and you want me to change action springs??? LOL

Artful, your google fu is better than mine. I came up with nothing but exterior ballistics and an interesting discussion on making a totally illegal firearm in 22LR for some unlikely SHTF scenario. You might get a laugh out of it if you can stand the stink of BS:

http://www.roguesci.org/theforum/showthread.php?t=2621

Maybe the guy doesn't want to get a red dot sight for his AWC Amphibian ;-)

I think I should provide some explanation. I'm sure that it is common knowledge that a long barreled 22LR is much easier to suppress than a pistol. In fact, with the appropriate choice of ammo and barrel length, you can achieve fairly low noise levels without even going with a suppressor. As the bullet travels down the barrel, the combustion gas gives up its energy to bearing friction and kinetic energy of the bullet.

What I am trying to do, and AWC has essentially done, is modify a 5 1/2" barrel in such a way as to simulate as closely as possible the effect of using a 26" barrel. The latter length is completely arbitrary but one to be known as quiet.

I can port the barrel and create a chamber to contain bleed off gas to simulate the volume of expansion. The obvious missing factor is the work of overcoming bearing friction of pushing the bullet further. So my next best step is to find a cut off point for the barrel and location for the porting to achieve a target velocity with Brand X ammunition.

I have a chronograph. So I can measure the velocity pretty easily. The trick is having the porting in the right place so that I can make adjustments. If I go too close to the chamber area, I will fall short and there isn't much I can do about it. If I'm a bit close to the muzzle, I can lengthen the ports (I plan to use slots) a bit. Trial and error. Probably a lot of error when you consider that I don't know what the bearing friction is.

The reason not to just buy an AWC Amphibian, besides the price, is that I have a different goal with regards to muzzle velocity and noise. I'm willing to go a bit louder and faster. As far as just getting a muzzle can, I'm also trying to go a bit shorter. Also I like the look a an integral. The constant diameter bull barrel look is aesthetically appealing to me and a lot of people won't recognize it as a suppressed firearm.

I am hoping that my design model which is based on patent 7,073,426 will provide the rest of the noise reduction as the bullet clears the end cap.

The red dot I got, btw, is a Burris FastFire 2. It's a pretty slick unit. And it is nice and small so that it works on a pistol.

[Rikky Lee]

22LR ammo varies from Lot number to Lot number. You seem to be proposing a lot of work for not much gain.

[pug]

Interesting but I still can't follow. You are going to have 5.5 inch ported barrel without a barrel extension? That usually means a ported barrel with an end bushing to support the tube. If you go that route then you will not be using packing in the entire length but baffles in the second stage? If I remember correctly with HV 22lr in a pistol you only have to drop 50 - 60 fps in order to get subsonic.

[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.