Going to do a rimfire can

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Historian
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Re: Going to do a rimfire can

Post by Historian »

Capt. Link. wrote:The nested K's used the face of the baffle to strengthen the cone or skirt of the preceding baffle.More weight is saved doing this as well as the density of metal is higher.With well designed Ks Hollywood quiet should be attainable in a 5-6 inch can going to 8 wont help unless the design is poor.
Is the efficiency of this length independent of diameter?

E.g.,ID= .75" Old PH;
1" some;
1.25" few;
1.5" very few.
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Re: Going to do a rimfire can

Post by whiterussian1974 »

Historian wrote:Is the efficiency of this length independent of diameter?

E.g.,ID= .75" Old PH;
1" some;
1.25" few;
1.5" very few.
There are some wave functions that only length (post expansion) can deal with. Volume handles the expansion of gases themselves.
A way to negate some of this is to add barrel porting to cause premature "uncorking."
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Re: Going to do a rimfire can

Post by Gunfixr »

Well, got the form 1 efiled.
It's going to be a 6" long can.

Going to do K baffles, I'm really leaning towards the titanium.
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Re: Going to do a rimfire can

Post by Gunfixr »

I have ordered the titanium.
I know, 4 times the price, I actually have the aluminum laying around I could use. But, it's not so much the price, even with the titanium price I'll only have $300 of cash in it, with the stamp. I'm not planning on getting rid of it, not planning on anodizing it, so this was the "durable" but lightweight option.
At the shop, I have a nice ultrasonic cleaner I use to get trigger packs and such on guns clean. It cleans the crap right out of a suppressor, but will vibrate off most any sprayed on finish. To keep aluminum from oxidizing, I'd have to put something on it, and then I couldn't just drop it in the ultrasonic.
Plus cool factor. There doesn't seem to be many titanium rimfire suppressors out there.

No word yet on the form, but it's only been 30 days, so not really expecting it back yet.
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Re: Going to do a rimfire can

Post by T-Rex »

Good to hear.

Do you have your design all finished?

30 days, I bet you hear something this week.
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Re: Going to do a rimfire can

Post by Gunfixr »

No, I haven't even had really any time to mess with it.

I am going to go with Ks.
Short blast chamber, I was thinking 3/8", but probably less, maybe 1/4". It's going on both rifles and a pistol.
I guess I can go with an SS first K, I think I have a piece laying around.
I know I have a piece I can do a thread insert with, as that was what I was going to do with the aluminum endcap.

Really, it's just the details. The tube is .065", so pick thread pitch, decide which particular K design. I almost blew it and ordered .875" bar, which would have left .005" to thread on. Got it changed to 1.0" one step away from completing the order. Was thinking more about how much material would go to waste turning down all the 1.0" to fit inside the tube than remembering I was going to have to thread the end caps. You have to order 12" minimum. Didn't know what I'd do with an extra 10" of 1" titanium bar.


Dad's next chemo will be coming up soon, and he's not fully over the last one. He's ok, at home, but still not back driving.
I've only been a week away from 3 weeks with a migraine every single day. All the tests found a minor heart problem no one knew about.
If I didn't pretty much work for myself I'd probably be unemployed by now, I've missed so much work.
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Re: Going to do a rimfire can

Post by Gunfixr »

My Form 1 email came back Mar 9 approved.
So, I can start anytime. I have my materials.
However, I am busy with my father's cancer and treatment, so I will get to this when I can.
It will be K's, 1" OD, 6" long.
Pretty much all titanium, I may do a SS blast baffle, don't know yet, may do a thread insert, may not, don't know yet. Since I work at an 07, I can play with titanium in these parts, and make replacements at work later if need be. Mt threads on my centerfire can are titanium and so far are looking good. The blast baffle is titanium and is looking good as well, which is why I am thinking titanium on all pieces here.
I will detail it with pics as I go.
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Re: Going to do a rimfire can

Post by Gunfixr »

Actually, this is the first Form 1 I've ever done for anything.
Everything I've got is on Form 4s.

So, I downloaded and printed the pdf approved Form 1 atf sent me. It is basically my form, but is marked "approved" down at the bottom, with a signature and date. Even still has the instruction sheets attached.
Is this correct?
This is my Form to keep for my records?
Or are they going to email or snail mail me something else?
There was nothing in the email to suggest one way or another, just a notifiaction of status change.

Form 4s that come back aren't like this.
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Re: Going to do a rimfire can

Post by AlabamaPaul »

That will be all you get...
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Re: Going to do a rimfire can

Post by whiterussian1974 »

There will be alot of LEOs who need retraining. It's hard enough to teach them that the ATF Form allows holders to possess otherwise "prohibited" items. :?
I STILL have to tell our deputies that MGs, SBRs, cans, and SBSs are lawful if the US Gov issues a Tax Stamp. :roll:
Even our ADAs often think that "Hollywood" guns are illegal.
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Re: Going to do a rimfire can

Post by Gunfixr »

Ok, well, when time permits, I can get started.
I got the longer threaded barrel made for the Bersa pistol. Just took a piece of barrel from cutoff, turned it to size, chambered it, threaded it and installed it. It works, and tried with a factory unit the shop owner has. Barrel diameter won't allow a shoulder, so it will bottom out on the muzzle.


I don't run into a lot of LE, but the few I know are pretty up on it here, several have stuff of their own, or have friends who do. Everything here in VA is legal, but for a few specifically named items, like the street sweeper.
You do have to register machine guns with the state police, but that's it.
There was an article, I think in a local paper, that there are more registered machine guns in VA than any other state.
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Re: Going to do a rimfire can

Post by Gunfixr »

Ok, been busy, what with life and all that's in it, but I finally got this done.
Well, mostly. It's made, and it works.
As mentioned, it's 6" long, 1"OD, all titanium. It weighs in at 5.3 oz. It has 7 K baffles, and the muzzle cap is a baffle.
The tube is .070" wall, and when I get it back to the shop again, depending on how much it weighs, I may skim about half that off and re-engrave it. But for now, it's still silver colored. I'll blast it, and if I don't like how it looks, I'll Moly Resin it.
It has no discernible first round pop, and every round sounds the same, at least on the pistol. The pistol is a Bersa .22, kinda looks like a Walther PPK, has just over a 4" barrel.
It's been fired next to two different Ruger MK II intergrally suppressed pistols by different makers. First is a newer SS one with HiViz sights, and it and my unit sounded identical to three persons present.
Second was an older gun originally done by Tibbets, but has been recently sent in for a rebuild. The people who rebuilt it put K's in it. This was done at an indoor range, and other people were shooting, so earpro had to be in use. However, best we could tell, his is either just barely quieter, or the tone is just different, neither of us is exactly sure.
I fired it on my 10/22 at the same range, but indoors with others shooting, it seems quiet, but I'll get a better feel for it later at the shop. Going to thread a bolt rifle as well, so will be able to compare semiauto and bolt guns.

Overall, I'm very happy with its performance. The others who owned the comparison pistols have owned suppressors for some time, and one for many years, with lots of exposure to many suppressors of many makes, and he was rather impressed. If I can trim an ounce or so off I will, but I'm not going to try to climb mountains to do it, I can live with it as is. I weighed one of the baffles before drilling the cross jet hole, and it came in at .2 oz, so my weight is most likely the rear cap and tube.

I have some pics, and need to take some more, but will get them posted soon.
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Re: Going to do a rimfire can

Post by Gunfixr »

Had fewer pics than I thought, but it's a start.

First is the tube. This is the rear end, showing the threads. I went with 28 TPI. I just threaded the tube's bore, going until they "peaked out" and noting the depth I had cut. Then, it's a simple matter to take the bore ID, add twice the depth of the thread cut, and turn the end cap to that measurement, then thread it, cutting until it fits how you want it.

Image

Next is the outside of the rear end cap. The threads for barrel mounting were also cut on a lathe, to be sure they are straight in line with the suppressor axis, and because tapping titanium isn't real fun. If you look down into the bore, it has a bottom with a clearance for the barrel bore. Also, there is a groove at the bottom. Because the pistol, and some rifles have thin barrels which will not have a shoulder for the end of the suppressor to tighten up against, this end cap will tighten up against the muzzle of the host firearm. When I thread a barrel, I typically recrown the muzzle with a flat recessed crown, so the muzzle is square with the bore, and can be used for alignment purposes. The groove takes an o-ring, a standard size available at places like Home Depot or Lowes, which is a tight fit on the barrel threads. Thus, the last couple turns are tight as the barrel is pushed into the o-ring before seating on the muzzle. This keeps it from backing loose during firing.

Image

Third is the inside of the rear end cap. This is the blast chamber, where the back of the first K baffle seats. As can be seen, it has a very small blast chamber, this counterbore is only .190" deep. The bore clearance is 5/16", enough over .22 bore size that a push rod can be used to push out the baffles for cleaning, if they are dirty enough to be tight.

Image
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Re: Going to do a rimfire can

Post by daPhoosa »

Very nice.

Baffle pictures coming next?
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Re: Going to do a rimfire can

Post by Gunfixr »

Yes, they are.
Got it to the shop yesterday, got my bolt rifle barrel threaded, and got to test it outdoors on the 10/22, the bolt rifle, and compare it next to the Stratus.
Also, got the rest of the pics taken, and the weights of the various parts.
Most of this hadn't been done because I was working on making the baffles on a Friday and Saturday, and finished them Saturday about 10 minutes or so after the shop closed. Well, Saturday is the end of the week, everybody (all 3 of us) is ready to go the hell home. So, I threw it together so I could run it out back and pop a mag of rounds through it, and see if it worked. When I had cut the groove in the back face of the baffles, I had gone real deep, to cut weight. Then, when I milled the cross jet, I realized that the thinness didn't leave much of a bevel to lead down to the opposite side opening in the front bell.
I was afraid the cross jet wasn't going to work, and I had just wasted all the most expensive part of the material. But, it was done, so there was nothing left to do but try it and see.
There is one big difference in the K's I have looked at and mine. If you hold the K so that you look across the cross jet cut from the one side to the other, they never line up with each other. They are close, but not actually lined up. When I cut my cross jet, I set up the baffle to take an endmill and basically drill the cross jet from the back, across the bore into the bell in one operation. The two openings are in alignment. Whether this is actually better or not, I don't know, but it did save time. There is evidence on the bell and in the tube of carbon and lead that blast is moving across the bore and to the outside, so it works.
Because of how I "drilled" the cross jet, the top edges of the lip around the bore were curved in, so I just opened them up straight by hand, with a Dremel. Also, in the bell opening, it made for a flat edge that leaned toward the bore, so with a small carbide burr in the Dremel I re-beveled that edge outward, to direct gases that hit that edge out. Only took a few minutes to do them all.
Anyway, on to the pics.
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Re: Going to do a rimfire can

Post by Gunfixr »

First, another of the rear cap, with the o-ring. The bore of the o-ring is fairly tight, just over 7/16". But, because of the radiused nature of the o-ring, if it were close to half inch, it would not have much bearing, and therefore not much grip to hold. This way, even though part of it wears quickly, it then leaves a wide area to grab the barrel. The friction is well noted when attaching the suppressor, and it hasn't moved yet.
Image

Then, is the front cap. Outside is a slot that a coin or other tool can be used to tighten or remove the cap with, Inside, the cap is cut to serve as the final baffle. Also, the bore is tapered, getting larger as it comes through the cap, a cone.
Image
Image

Next are the baffles. First pic, they are in order. On the left is the can's muzzle, to the right, the one closest to the muzzle of the gun. Second is a closer pic so more details can be seen. Third pic is the blast baffle on the left, with one of the others on the right. It is noticeably thicker in the nose, and also in the bell, as well as the bottom of the flange. It's about .060" thick, where the rest are in the .040-.045" thick range. There's been maybe 100rds shot through it so far, it's been run through an ultrasonic, so a lot of the carbon is gone, but you can still clearly see the blast patterns.
Image
Image
Image
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Re: Going to do a rimfire can

Post by Gunfixr »

Now for the weights. It is clearly seen that all the weight is in the tube. The baffles are at about 1/4 oz, the front cap is under 1/4 oz, the rear cap is 1/2 oz, but the tube is right at 3 oz.
The tube is .070" wall. Compared to factory aluminum units, they have aluminum tubes of .049" wall.
As Ti is quite a bit stronger, I don't see why I couldn't turn it down to about .040" wall without it still being plenty strong enough. I used 28 TPI threading at both ends, and it only went about .020" to maybe .022" deep.
As not quite half the tube wall would be removed, not quite half the tube weight would be removed. This would mean somewhere between 1 and 1 1/4 oz. While not a lot, weight wise, it's a significant percentage of the total weight.

Blast baffle:
Image

The rest of the baffles:
Image

Rear cap:
Image

Front cap:
Image

All the baffles:
Image

The tube:
Image

The assembled suppressor:
Image
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Re: Going to do a rimfire can

Post by Gunfixr »

Ok, so I got to try it on the 10/22, and a bolt action .22 rifle, and I got to compare it to a Tactical Innovations Stratus.

I had earlier stated that on the Bersa pistol, there is no discernible first round pop, and that all fired rounds sound the same, which it does. Firing a lot of cheap bulk ammo results in some sounding a bit different here and there, but it's random, and I believe due to ammo, and the guns will sound like this with cheap ammo unsuppressed as well.
On the rifles, however, it is a bit different. With subsonic ammo, it's just stupid quiet. If you don't see something happen downrange, it's almost as if nothing left the barrel. There is action noise with the 10/22, with the bolt gun, it sounds like a weak air rifle.
With full power ammo, the first three rounds are just a bit louder than the rest. If you wait a bit, then that "resets" itself. Not a first round pop, but the first ones are barely, but noticeable, louder. Still way hearing safe.

The Stratus doesn't do this. I have had it apart. It has 6 K baffles (mine has 7), and it has a longer blast chamber. I do believe mine sounds barely better on the pistol, but they sound the same on the rifle, after the first three out of mine.

I'll have to do some more on this. I was by myself, as one of the guys who comes to the shop wasn't there, it was just me and the owner, so he couldn't come back with me. So, it was just me, behind the gun, no one off to the side. Also, after 20+ yrs of machine shop experience, my hearing is not so great, and I have a real good case of Tinnitus in both ears. The other comparisons I have listed previously have been from witness observations. So, this is first impressions, but I will get witnesses and get back, and get more models to compare to, since it's never difficult to get people to show up and shoot stuff, especially with suppressors.

I put mine on the full auto 10/22, it has about a 12" barrel, it's open bolt. It was quieter, but not all that impressive. I think a lot of action noise, and of course a lot of supersonic bullet cracks real fast. It'll dump an entire 25rd mag in just over a second.
I didn't start trying to acquire subsonic ammo until recently, and I'm sure everyone here knows how hard that is. I have only 2 boxes, and most of one is gone playing with this already, so dumping half a box in one second just to see wasn't prudent.
I used to shoot a lot of rimfire 3P matches, and still have a lot of match ammo, which is subsonic, but more expensive. So, I'll use it, but not going to just blow it off.
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Re: Going to do a rimfire can

Post by muellerdeal »

keep up the good work!
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Re: Going to do a rimfire can

Post by Gunfixr »

Ok, so I did two things.
One, I turned down the OD of the suppressor to get rid of some unnecessary weight. I turned the tube from .070" wall down to about .040" wall. This took the OD from 1" to about .940", and gave almost a full sight picture on the pistol. It also took the weight down by almost 2 oz, from I think 5.9 oz to about 4 oz.
Not bad for a .940" OD 6" long suppressor.

Second, to try and eliminate the slightly louder first round sound, I had drilled two small (about .060" holes in the baffles at 180 degrees apart, with the cross jet cutout in between. This was to vent into the area outside the cone of the baffle, and I did it to the first 4 K's only.
It was louder.
So, I welded up one of the holes in each baffle, to cut it down to one hole each.
Bingo.
The first round and subsequent rounds sound the same, and still scary quiet with subs. Apparently, the two holes symetrical was not a good idea, the one hole created better turbulence.
The very small hole does vent, without being truly an opening, making the outside area part of the blast chamber.

The o-ring inside the back cap does wear a bit quickly, but it's size still leaves it tight. So far, it has not come loose during firing, even on the semiautos during rapid fire, or on the full auto.
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Re: Going to do a rimfire can

Post by fastfire »

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Re: Going to do a rimfire can

Post by Matt in TN »

Very nice build and details! Can you post a pic of your modified baffles? I'm having trouble understanding where you finally ended up with these.
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Re: Going to do a rimfire can

Post by a_canadian »

Sounds like a pair of Dater holes in each of the four first K faces. Convention is to put one Dater into the first K face. A hole in each of the first four would still seem a but much, but hey, if it works that's great!
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Re: Going to do a rimfire can

Post by Gunfixr »

Image[/quote]

I hadn't taken any more pics, I can if this explanation doesn't help.
If you look at the above pic, and add two holes, one on either side of the center, pretty much centered in the face groove, right at .060" in diameter.
I did this to the first 4 baffles.
I was louder, and inspection showed fouling going through all 4 sets, so the holes on the 2nd, 3rd, and 4th baffles were doing something.
I welded one up on each baffle, the same one, as I install the baffles each turned 90 degrees to the previous one, so the cross jets aren't aligned. Basically, I just made a puddle and they closed, figuring the surface imperfection might add to turbulence.
It went back to quiet, and the first shot no longer discernible from later shots.

So now, if you use the pic above, there is a .060" hole in the center of the face groove, 90 degrees to one side of the cross jet cut. They are all on the same side.

And, I sprayed it with black moly resin.
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Re: Going to do a rimfire can

Post by Gunfixr »

I did not know what convention on holes was, or even if it was used.

I did notice that on the comparison suppressor, that didn't have the problem, the blast chamber area was larger. I hoped that the hole would increase the blast chamber some, by allowing the area outside the cone to become part of it, and, with the cross jet and hole, might add turbulence, which I thought was a good thing.

I think the two holes, 180 degrees apart, was too symmetrical, and canceled the desired effect.

This seemed easier than redoing the baffles, as the stack length is important.


Fouling does go through the holes in all four, but I don't know if it does much. Later, I realized that the inside of the cone was in front of the next three baffles, instead of the small area in front of the first one, and I may have been just wasting my time. But, I had drilled them already, so left it.
In retrospect, I probably should have drilled one hole in the first and tested, but it is what it is.
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