Final material choice help please

[garredondojr]

I'm nearing the home stretch for my form 1 stamps to clear (at 225 days) I'm pretty dead set on using 4130 and 4140 for my 30 cal suppressor but still undecided on my 9mm suppressor.

my 9mm is submitted at 8" length and I'm looking at doing it 1.375" diameter. now the purpose of this suppressor will be 22lr, 9mm pistol, 9mm ar, and hoping 5.56 11.5" sbr for HD use only (the 30 cal can will be primary on the 5.56)

Since I do want to test 5.56 and it not grenade is where my design parameters are going to be tested. here is my thoughts and looking for opinions. keep in mind I don't want it to be a boat anchor.

originally I planned on doing a full Ti can but I'm not sure I want to go that route and waste a bunch of money on material if my equipment isn't up to the task. (8x14 lathe)

so now I'm leaning towards 17-4 blast baffle (stepped 60'), with a 17-4 blast chamber insert that will also serve as the mounting threads/endcap then I was going to do a 7075 t6 tube and modified k-baffles for the rest of the suppressor. I've even considered making the first K from 17-4 for added insurance. I'm thinking a 1.5" blast chamber but the recoil booster will go into the can to reduce oal and lessen frp (going to be doing a griffin style mounting system and making my own booster for the pistol) for the 22's i'll make otb mounts to also lessen the blast chamber volume

any insight or reccomendations would be greatly appreciated. Thank You, George

[partsguy22]

I don't think Aluminum Ks belong in any can that will see 5.56 SBR use, they will have to be way over built to keep from collapsing due to the thrust on the skirt (there are ways to prevent this)

If you build the can strong enough for 5.56 SBR use it will more than likely be to heavy for hand gun use , plus a 1.375" can really doesn't have enough volume for that any way

If it were me id just leave the .30 can on the SBR

and keep the 9mm can for your 9mm and 22

ETA:

IMO if you want a can like you describes you might want to go the all Ti route and make it with just 60* cones your lathe should be fine you will just have to take lighter cuts

[garredondojr]

partsguy22 how would one prevent skirt collapse? I was thinking of threading the blast baffle and blast chamber together to lessen the thrust on the remaining baffles. do you feel the others would still be at risk? I just might have to use the 30 cal solely on the 5.56

[partsguy22]

nesting baffles ,threading the baffles in to the tube or threading the baffles together then putting them under tension


I think Capt Link has done the fully threaded tube with screw in baffles
and Curtis Tactical does the Screw together K Baffle Monocore
you may search for them and see if those Ideas will work

[mcmaster]

Threading baffles together is likely going to make them heavier than welding them.

[fishman]

I guarantee your 8x14 large can handle titanium alloy. Look at my form 1 build, I did a titanium 30 cal can with a much smaller lathe

[BinaryAndy]

As Partsguy22 said, aluminum baffles or tubes and 5.56 SBR's don't mix well, for several reasons. The strength drops dramatically when it gets hot, much more quickly and at lower temperatures than steel or titanium. It's also susceptible to fatigue failure, and the combination of repetitive stress and high temperatures in a rifle can makes that a very real and not easily predictable concern.

Your lathe should do fine with Ti, it'll just be difficult and slow. 17-4 is always an excellent choice. Hardened 4130/4140 with the right surface treatment to prevent corrosion is even better.

You might want to consider using 17-4 for the baffles, blast chamber and caps, with a titanium tube. Of course a lot of things would work for the tube, but for some reason somebody has decided that no high-strength metals except 4130 should ever be readily available in tube form. Seriously, of all the metals that you can find in tube form, Grade 9 Titanium and mild steel are pretty much tied for second (next to 4130) when it comes to yield strength. So, if you want a corrosion resistant tube and you don't want to send out 4130 for surface treatment, Ti is your best choice for strength and weight.

If you do use titanium for the tube, I would recommend using something else for the end caps. Threading Ti into Ti is the ultimate recipe for galling.

[partsguy22]

I thought the galling issue was only an issue if the parts were the same alloy ?

[BinaryAndy]

I thought the galling issue was only an issue if the parts were the same alloy ?

It's a bigger issue if they're the same alloy, but it's always a significant issue with Ti-to-Ti threads, especially fine threads. There are surface treatments that mostly cure it.

[PepeLapiu]

A can for both 9mm and .223 SBR?
I don't think so, unless you make it all Ti to save weight.
K baffles are really what you would want for rim fire. Cone baffles for centerfire rifle calibers. I wouldn't use K baffles for either 9mm or .223.

A .223 can will be too heavy for a 9mm pistol.
And a 9mm pistol cal will require a LID on it so you would have to have two mounts for that can.

Start with either a 9mm can or a .223 can, not both in the same can.

[fishman]

A can for both 9mm and .223 SBR?
I don't think so, unless you make it all Ti to save weight.
K baffles are really what you would want for rim fire. Cone baffles for centerfire rifle calibers. I wouldn't use K baffles for either 9mm or .223.

K baffles work great for 9mm, 45acp, 300 blk, and even 308.
Cones are more common with centerfire rifles because they're cheaper to machine, and work almost as good or a little better, depending on the application.

My k baffle 458 silencer sounds fantastic on my 450 bushmaster

[gunny50]

A can for both 9mm and .223 SBR?
I don't think so, unless you make it all Ti to save weight.
And a 9mm pistol cal will require a LID on it so you would have to have two mounts for that can.
Start with either a 9mm can or a .223 can, not both in the same can.

Well, here we see a perfect sample of many minds many ideas.
Use of (thin) 17/4 tubing seamless will solve the weight problem, and still be strong enough when designed right.
Ti can be done for a 556 SBR but that won't be light or hold up to blast extremely long.
Right wall thickness on the blast chamber and a well designed blast-baffle will help for the 556 use, keep in mind that making it for 9mm will give a good portion of gas blow by and will reduce pressure in the system to.
Fixing the LID problem is even easier, replace the spring with a well fitted spacer/ blast cage and your done.
PS use 1/2x28 on both 9mm and 556

I think a design like the SilCo Omega K would do well if walls are adapted for SBR use.

Gunny

[garredondojr]

Thank you guys for alot of great responses. I think the ability to be used on the 5.56 sbr is going to complicate things more than needed so the 30 cal it is for the sbr. the 9mm can will be regulated to the rimfires and 9mm.

after alot more reading its looks like aluminum is a no go. didn't take cleaning into consideration with the 22lr being in the picture. and having the ability to "dip" the baffles for ease of cleaning is a great feature. which leads me to a new question.

BinaryAndy you have really caught my attention with the 4130,4140,4340. I was reading some of your testing with these materials and how their strength will allow for thinner construction thus equal or close to finished weight of a Ti can. however you did mention corrosion coatings. how critical is the coatings? would parkerizing and cerekote be sufficient?

gunny50 do you have a link or source to 17-4 seamless tubing?

again thanks to all who have posted guidance and their findings.

[garredondojr]

also on the subject of 17-4 which of the heat treat's which is most desireable for a machine it and done approach? h1150?

[gunny50]

gunny50 do you have a link or source to 17-4 seamless tubing?.

I'm not in the US so where I buy it would not help you.

Do some googlefoo.
http://www.futuremetals.com/products/tu ... temp-tube/

Gunny

[fishman]

Use of (thin) 17/4 tubing seamless will solve the weight problem, and still be strong enough when designed right.
Ti can be done for a 556 SBR but that won't be light or hold up to blast extremely long.
Right wall thickness on the blast chamber and a well designed blast-baffle will help for the 556 use, keep in mind that making it for 9mm will give a good portion of gas blow by and will reduce pressure in the system to.
Fixing the LID problem is even easier, replace the spring with a well fitted spacer/ blast cage and your done.
PS use 1/2x28 on both 9mm and 556

I think a design like the SilCo Omega K would do well if walls are adapted for SBR use.

Gunny

17-4 and grade 9 titanium have very very close strength to weight ratios. the titanium is a tiny bit higher but 17-4 would probably pass it up if you get the can super hot. thinning out your tube and switching it to 17-4 wont gain you anything. since you cant weld or braze 17-4 tube to grade 5 TI endcaps, i would still reccomend TI tube unless you are doing stainless caps or threading the caps.

i do agree with the use of 17-4 for any blast baffles or blast baffle spacers, due to its higher strength. i did that in my 300blk can.

[BinaryAndy]

BinaryAndy you have really caught my attention with the 4130,4140,4340. I was reading some of your testing with these materials and how their strength will allow for thinner construction thus equal or close to finished weight of a Ti can. however you did mention corrosion coatings. how critical is the coatings? would parkerizing and cerekote be sufficient?

The early Silencerco Sparrows had steel tubes (almost certainly 4130) which I believe were just parkerized. There were occasional reports of rusty tubes, but it generally worked.

SRI (Bender) used to get those tubes refinished with Melonite (salt bath nitriding, same thing as Tennifer), which is actually a case hardening process. The result is much better corrosion resistance than parkerizing, increased fatigue strength, and a hard, wear-resistant surface.

Plasma Ion Nitriding is a small improvement over salt bath nitriding with similar results.

PVD coatings would be great except they won't reach the inside of the tube. CVD coatings would be even better, and they would reach the inside of the tube, but they're incompatible with 4130/4140. Excellent option for 17-4 though.

Boronizing is pretty much ideal, super-hard, wear resistant, tough, low friction, extremely heat resistant. I think it's kind of ugly though. Maybe you could cerakote over it.

"Hardite" is apparently a Tungsten/Tungsten carbide-based low-temp CVD coating that is compatible with 4130/4140. I don't know too much about it, but it should be similar in a lot of ways to boronizing. Including the color.

4130 and 4140 are similar in strength to 17-4, but only if they are heat treated properly. You more than double the yield strength when you harden these alloys. There's no point to using them if you don't. Parkerizing doesn't affect the heat treat, so in that case you would be fine to start with pre-hard 4140, and I think you can find pre-hard 4130 tube as well, though that's a little more difficult. Boronizing is a high-temperature process, so it basically anneals your parts and you have to get them heat treated afterwards. Nitriding is actually a case hardening process. Since silencer parts have really thin walls, if done right the nitriding will bring the core of the metal up to an appropriate hardness while also making the surface much harder for wear resistance.

For the rimfire suppressors we're working on, we've actually settled on a duplex coating process, involving plasma ion nitriding and something else.

[garredondojr]

Thanks again everyone.

so I'm now leaning to full 17-4 internals on possibly both now. just had a few last questions.

I found 17-4 h1150. is this machineable in this state? and would I be able to run it as is after machining? I wouldn't know anyone to heat treat it to H900 for me after machining and the legalities of that are pretty restricted.

does 4130 actually rust when covered in carbon? the exterior I'm sure would be fine with cerekote I assumed the inside would be protected by the carbon that would form from firing. I just assumed that I guess, as most rifle barrels are chromoly granted a different grade and they seem to do fine, granted the copper fouling could protect it I assume.