Critique my 22LR design Updated 7-25-2012

[sst4270]

Hello all,

Please critique my design. It was inspired by SBR's post. Since I'm an mech engineer by profession I couldn't help but do a full 3D work up.
Awaiting Form 1 so I wanted to get as much feedback as possible prior.

Some questions I have in particular:
Bore size is currently @ 0.240". I think that will be too small. SEE UPDATE
1/2" - 28 barrel thread is only 0.375" engagement. I think that is also too short. I should probably lengthen that to at least 1/2". SEE UPDATE

A couple of other things:
I noticed a couple of typos. Please don't be too harsh on those.
The K-baffles will be hard coat anodized
Calculated weight is coming in just under 8 oz.

Thanks in advance for your feedback.

Regards,

SST

REV. B: Updated the drawings based on your feedback.
Removed spacer, added "snout" to inside of outer endcap, increased bore to 17/64 (optional: increase bore in stepped increments from baffle 1 to baffle 7)
Overall length has shortened by approx. 3/8", increased length of 1/2-28 threads for more engagement onto barrel.

REV. C: Updated the drawings based on your feedback.
Added chamfer to snout on outer endcap directing gasses internally
Shortened last k-baffle to fit inside outer endcap - This shortened the OAL again. (This is about as short as I can go because this is being built to go onto a Tacsol SB-X barrel. If I shorten the suppressor much more I won't be able to install/remove it by hand easily.)
Added a little meat to the 'waist'.
Changed material of outer endcap to aluminum.

On another note: I notice there doesn't seem to be a common set of terms when describing the features of a K-baffle. I see various terms used for the same features causing a lot of back and forth chatter. There should be a sticky on this forum that calls out a standard set of terms for the various parts of a K-baffle. Such as: skirt, waist, rim, this hole, that hole, etc... or whatever.

Anyways here are the latest drawings:

[Bendersquint]

Way too tight a bore.

Should be at least .264 at the tightest.

[CharlieBravo]

I just finished my first can, a .22 can that I overengineered so that I can use it on a AR-15 eventually. I made the exit hole 1/4". It works great on my 10/22, would that be pushing my luck with the 5.56? Bendersquint, I followed your suggestion on wall thickness, it's over 0.065 inches thick, 304 stainless steel. Thanks.

[SRM]

I have a couple suggestions. Bein you`re goin aluminum, you need to change the waist of the skirt. Needs to be stronger. There are different ways to do this but its up to you.
Don`t make the bore too tight. Even if everything is perfect strait, you want around .02" clearence all the way around for bullet stability.

The end cap does not need that much of a chamber. I don`t think its bad though. My f1 can is supper efficient. You may not need seven baffles.

Just thinking out loud here. Nice work there too!

[SRM]

standard thread length for a .22 can is .400".

[twodollarbill]

Way too tight a bore.

Should be at least .264 at the tightest.

17/64" drill bit if anyone was wondering

[Bendersquint]

Way too tight a bore.

Should be at least .264 at the tightest.

17/64" drill bit if anyone was wondering

+1

[Hatchetjoe]

Why the spacer? It will increase the blast chamber and likely increase FRP.

[ChimeraPrecision]

looks nice. (solidsworks perchance?)

Does anyone know if the baffle interlock devices are pateneted? If this feature is patented you will need permission so you don't infringe on someones intellectual property.

are you going to harden the 17-4 after machining operations?

[Bendersquint]

looks nice. (solidsworks perchance?)

Does anyone know if the baffle interlock devices are pateneted? If this feature is patented you will need permission so you don't infringe on someones intellectual property.

are you going to harden the 17-4 after machining operations?

What interlock devices, the slots and groove? I believe they are patented but not enforced. They are patented as a baffle alignment device or something like that.

[SRM]

Why the spacer? It will increase the blast chamber and likely increase FRP.

Interestingly enough, mine didn`t. No dater hole either. Lots of back pressure though.
I shot it wet the other day and what a mess. Didn`t make it quieter either. Sounded the same as dry.

[sst4270]

Thanks for all the tips...

Regarding the bore... No problem. I'll enlarge it.

Software is Pro/Engineer Wildfire

Regarding the spacer... I can eliminate it. I really just wanted something in there to allow me to tighten everything up nice and tight. The spacer affords me that since it will be made last and turned to the length I need to get everything tight. But I can just as easily cut the tube threads just a little deeper and then cut the tube length down as needed to get the final fit just right.

Regarding the interlock feature... Even it was patented... It would (generally) only be an issue or concern if I was intending to mass produce. Since this will be a one-off item most companies couldn't care less about that kind of infringement.

Regarding thicker skirt on the baffles... I'm fairly certain that will not be an issue with 7075. Is it strength you're concerned about? The first baffle will be 17-4 PH Stainless. (Though I have yet to calculate/simulate internal pressures.)

thanks again,

SST

[57fairlane]

My $0.02 . . . since you are making each baffle, I would start the blast baffle out at .250 and every other baffle bump it out to the next size (looks like F, G, then 17/64") if you are really going after it.

I would also keep the front end cap the same and bring a snout out 300-.400 or so. inwards towards the rear.

[ChimeraPrecision]

I understand most companies wouldn't care but it's still infringing on their intellectual property. Regardless, build it. Looking forward to the final product

[daviscustom]

I haven't built one like this, but isn't that endcap adding a lot of extra length for very little return? Just thought by that point hopefully that kind of volume is overkill....I would think it could be redesigned to save a 1/2" of length.

Maybe you guys that have built K's disagree, I'm curious to hear your opinions on the subject.

You could make the cone on the front baffle fit inside the endcap and have a counterbore in the cap to set the length of the front endcap chamber.

[SRM]

I haven't built one like this, but isn't that endcap adding a lot of extra length for very little return? Just thought by that point hopefully that kind of volume is overkill....I would think it could be redesigned to save a 1/2" of length.

Maybe you guys that have built K's disagree, I'm curious to hear your opinions on the subject.

You could make the cone on the front baffle fit inside the endcap and have a counterbore in the cap to set the length of the front endcap chamber.

I Was thinking this too. I`m thinking you could loose a baffle also. That could loose a 1 1/4" off the length.

[sst4270]

Points all well take guys. I'll post an update design tomorrow night.

Thanks,

SST

[Historian]

Very nice work and presentation.

For historical reference, the Pre-WW II Parker Hale .22 suppressor also measured
1" O.D. , .75" I.D., 6+" in length. Its stamped baffles produced a sound reduction
that set the standard for many years.

<< http://www.youtube.com/watch?v=aGrGCnStmrk >>

It will be most interesting to see the results of your incorporating the modern K-baffle
technology.

Best.

[daviscustom]

In your updated endcap ( if it was mine) I would put the chamfer on the OD of the "snout" instead of in the bore. I would avoid doing anything that would tend to funnel the gasses out the bore. The snout shouldn't have to be that thick either, which would leave more volume to catch that last little bit of blast that makes it to the end. Still don't think that endcap needs to be that deep, but if it's going to be that size I say make it more volume and less metal...especially out on the end like that you don't want a lot of unneeded weight.

I would also lean towards changing that front endcap to aluminum as well....will make it less muzzle heavy....most noticeable on a pistol.

You may be a "stainless" kinda guy.....if so you don't care about the weight, but stainless is not really required anywhere on a 22lr can unless you are thinking full auto or frequent high cap. mag dumps.

[Bendersquint]

In your updated endcap ( if it was mine) I would put the chamfer on the OD of the "snout" instead of in the bore. I would avoid doing anything that would tend to funnel the gasses out the bore. The snout shouldn't have to be that thick either, which would leave more volume to catch that last little bit of blast that makes it to the end. Still don't think that endcap needs to be that deep, but if it's going to be that size I say make it more volume and less metal...especially out on the end like that you don't want a lot of unneeded weight.

I would also lean towards changing that front endcap to aluminum as well....will make it less muzzle heavy....most noticeable on a pistol.

You may be a "stainless" kinda guy.....if so you don't care about the weight, but stainless is not really required anywhere on a 22lr can unless you are thinking full auto or frequent high cap. mag dumps.

Most manufacturers have a snout(as you call it) at the end of the endcap.

I do think its a bit too long but not uncommon at all.

[alemonkey]

Your updated design looks almost identical to my F1 can that I just finished, except as others have suggested the endcap on mine is aluminum and the final baffle fits inside it. I also have 7 baffles with the first being stainless, but my can is 1.125 OD. I am very happy with mine so I think yours will work well.

Edit: I do have a little thicker neck where the cone meets the flat, to make it stronger. I was paranoid about a baffle collapse.

[sst4270]

Thank-you all again for the feedback.
It's been very helpful for me to gain a better understanding of the internal details of this thing as well as the individual functions of various internal features.

I'll try to get a revised model up soon.

Also since this is modeled in 3D I can provide those files to any of you interested.
I will be machining mine using a combination of manual lathe and CNC mill.

Regards,

SST

PS Is there a way to attach a STEP file to a post, or does it have to be sent as an attachment to a PM?

[ChimeraPrecision]

Thank-you all again for the feedback.
It's been very helpful for me to gain a better understanding of the internal details of this thing as well as the individual functions of various internal features.

I'll try to get a revised model up soon.

Also since this is modeled in 3D I can provide those files to any of you interested.
I will be machining mine using a combination of manual lathe and CNC mill.

Regards,

SST

PS Is there a way to attach a STEP file to a post, or does it have to be sent as an attachment to a PM?

Upload the step file to deposit files the post a link.

[palladium]

Nice design. But can I give you some advice to save money on machining and on the matérial without reducing the performance and to reduce the weight. I recommend you to use the 28 T.P.I. tread pitch because the tread is less deep in the tube and the tread are more fine. Maybe some have a different opinion, but I think it is very good advice to follow. Look the pic.










This is some example of my .22 desing

End cap










Front cap

[Bendersquint]

Machine it right from the get go and you won't need to take up tolerances with a spring.

You should NEVER use a spring inside a silencer.