K-Baffles: 60° or shorter to fit more of them?

[Quietiskept]

I’m waiting on a form 1 and having fun drawing up plans for when my stamp comes and I can make some chips.

I spec’d a 6” 9mm can but I plan to shoot 22lr and 30 cal subs thru it too. I decided to do K baffles.

60° cones seems like a pretty standard sweet spot for a number of successful cans but I have seen some Ks with shorter baffles like 45° or 50° cones.

I guess the advantage is that for a given length you can fit one more cone in there? More metal to absorb heat and baffling to swirl & delay the gas is good but there has to be a spot where you get diminishing returns from either taking up too much can volume or using too blunt of an angle to effectively strip or trap gas?

I would love to here some opinions!

Thanks

[YugoRPK]

K baffles work better than cones on pistol type rounds. They do. Once you get into supersonic rifle stuff cones work better.,

[Quietiskept]

Yeah I’m not talking about 60° cone baffles I’m talking about the cone that sticks off the back of a K baffle.

So is there a disadvantage to making the cones on the back of the Ks shorter with a steeper angle so I can fit more baffles in there? At what point do you get diminishing returns?

[Quietiskept]

And apologies if this question is beat to death I did search it but technology and consensus change fast sometimes with this stuff. Some of the threads I was reading were from when mouse holes and dater holes were more prevalent, which now seem to not be so common.

[a_canadian]

A single Dater hole 1/16" in the first K is fine, especially with a very short initial gap - 1/4" between muzzle and the first entry point in the baffle is about right for .22lr. With supers that might be a bit small, but the Dater hole relieves some pressure making it okay. With subs the combination helps with efficiency while reducing or eliminating first round pop (FRP).

The problem with a long nose on the back of a K is that this sort of design inherently lengthens the 'tunnel' in that K baffle. The more overall length you have in the suppressor where the bullet is surrounded by metal, the less efficient the suppression. You want to design a K so as to keep this interval to a minimum while at the same time effectively redirecting a substantial portion of the gas jet across the bore and into the expansion volume outside the cone. A longer you make that 'cone' the more metal the louder it gets. This is part of why I like my K baffles short for .22lr, between about 0.55" and 0.6" long. I can stack more into a given length of tube, and with a flatter-angled cone and slightly sloped rear skirt cone I get both a stronger baffle than if the skirt is essentially flat, minimal metal between nose and inside of the main cone, while having plenty of metal to carve a scoop on one side of the face and a vent in the waist without weakening it significantly. Looking at this cross-section again, seems to me I did dig in a bit excessively with the scoop, but it's 7075 and I only shoot subsonics so it'll last a very long while.

[Quietiskept]

So that’s a strong vote for shorter than 60° cones. Thanks for the pic it’s nice to see different K cross sections!

From hours of internet snooping I’m kind of getting a picture that the slower the bullet the more likely stuffing more K’s in is the ticket.

Seems like the 60° cone shape might be more optimal for stripping or containing expanding gasses at higher velocity. It seems that 22 can use a blast chamber that’s even smaller than the volume inside and outside the first K, and having a cone shaped blast baffle with a decent blast chamber might be most helpful with a more energetic roond like 300 whisper or blackout.

I’m planning to feed this can a diet of mostly 150g 9mm subs and 22lr so I am leaning heavily toward a 45° or 50° cone angle on my Ks mostly depending on how many I can fit.

I’d also like to index the baffles to each other with little interlocking tabs. I’ve seen 180° alternating cups and ones where the vents and scoops were all the same. Does either design have advantages in practice?

[a_canadian]

I'd not use the same can for .22lr and 9mm. Tried that, and performance with .22lr through the much larger baffle bore is very disappointing. But hey, your call. It'll certainly suppress the noise, just not nearly so nicely as a dedicated .22lr suppressor.

I typically flip my K baffles 180 degrees, zig-zagging down the line. I find this ever so slightly quieter than lining them all up the same way. Not hugely significant though. I don't try to get too precise about it, just in the ballpark, but it is important to reproduce the same approximate arrangement. With subsonic .22lr I've found that surface effects are significant, such that if for example I rotate the whole stack by 90 degrees, my point of impact will be very significantly different. This on multiple guns each with their own dedicated suppressor, and varying from 4" long to 9" long. The longer the tube and hence more baffles, the more significant the change. I've given up on such long ones, as there's really very little advantage in going longer than about 7" overall (about 6" of actual baffled space, plus rear plug and blast chamber, plus front cap). So my habit now in order to maintain POI is to clean the tube and baffles, mount the tube on the gun, then load the baffles in the same order every time, starting with the first K venting up, second down, etc. Works for me. If interlocking tabs are something you can easily make then by all means do that.

Last week in messing around with a new 10/22 I thought to try out conical baffles. Made a set which nest a little, integrated tubular spacers, clipping them like Rusty did which seems popular, the 'DHC' pattern of symmetrical clips which supposedly maintain better accuracy than K baffles. Metered about 1.5dB louder than some old K baffles in the same can. Interfered with the bullets somehow, causing a bit of tumbling, though alignment is perfect with the short Dlask bull barrel. Even after boring the holes out a bit larger. Go figure. So I'll replace those with K baffles. I don't know why they didn't work in this experiment, but with all the extra 7075 needed to make them compared to K baffles and frankly less fun time at the lathe with the deep countersink boring for the spacer and inside of the cone, I'm happy enough to stick to what works better.

[Quietiskept]

Hey

So my stamp finally came in. I ended up stuffing a bunch of K baffles in my 6” by 1.5” tube. They’re all pretty close to the same but I let some very slight variations creep in figuring it would help to dampen different frequencies.

I dunno if it’s just because there is so much volume for 22 in it or what but 22lr made subsonic with a chopped 4” barrel on a ruger mkIII is plenty quiet. 9mm subs are only a little louder and both are comfortable to shoot all day with no ears on. I made some mousefart loads for my 308 savage99 levergun and it is rediculously quiet too.

Overall I’m really happy with my first effort. I will definitely be applying for a couple more in the future- I want to try my hand at a 30 cal can for supers and a dedicated 22lr can to see if it can be a lot quieter.

Thanks for the responses they were very helpful!

[bedwetter904]

So good to hear your K baffle design turned out well! I am waiting on my first forum 1 stamp to come in for a k baffle design. How did you drill your holes? Did you have a lathe? I only have access to a drill press and am worried I'll screw it up.

[a_canadian]

Buy some washers the same OD as your undrilled baffles, with the same diameter centre hole, or drill them out to the size you want for your baffle bore. Make a clamping fixture which can hold a stack of these washers securely in the drill press. Locate the clamping fixture such that the drill spins freely in the washer stack, then swap out washers for the baffles and drill them. Alignment should be fairly decent.