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Posted: 9/4/2019 11:55:40 AM EDT
| Anyone have an absolute minimum wall thickness for a 308 tubeless welded can out of 316 ss? |
| 316 stainless isn’t as strong as other common materials and they all(mostly) get weaker with increasing temperature. For reasonable use something around 0.065” has been used by a lot of Form 1 builders. Varying wall thickness, welded in baffles or mounts/front caps, heat sinking muzzle devices, thread pitch and depth of cut on threaded caps, etc. all impact safety margin and severity of use tolerated. A lot of commercial cans with a 304 tube will have an all welded core that carries the load. |
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Some design details. I will be doing some 2inch diameter pistol cans for sub guns and a 1.75 inch rifle can for a Scar 17 and mk20. They will all be tubeless, welded designs with 60 degree cones nesting into each other and the end caps. The baffles will be spaced anywhere from .300 to .75 in away from each other. What im wondering is whats the minimum thickness on the "wall" of the baffle and where they butt together.
Ps, I originally was going to try grade 5 titanium but the cost and possible weld integrity issue decided on a stainless option. |
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Quoted:
Some design details. I will be doing some 2inch diameter pistol cans for sub guns and a 1.75 inch rifle can for a Scar 17 and mk20. They will all be tubeless, welded designs with 60 degree cones nesting into each other and the end caps. The baffles will be spaced anywhere from .300 to .75 in away from each other. What im wondering is whats the minimum thickness on the "wall" of the baffle and where they butt together. Ps, I originally was going to try grade 5 titanium but the cost and possible weld integrity issue decided on a stainless option. |
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It honestly depends on your welding skills. You could probably get away with.050" blast chamber and .030" for the rest, but it'd be real easy to blow holes through it, collapse skirts or end up with a banana shaped suppressor. I'd recommend .060" for blast and .050" for the rest, maybe thicker if you're not sure on your welding. |
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To add to 66 duce's rec I had seen a trick setup of a simple v-block using plastic pulleys with o-rings and one of the wheels was run to a variable speed motor. He experimented with different speeds and amperages to get a nice fusion weld. the torch was set in a fixture above the weld seam to keep the torch distance/angle consistent then just turn on the motor step on the pedal then let off once 360' was achieved, moved the torch to the next seam and repeated till completed.
He left a decent sized register where the two baffles met to prevent a blow through and lightly beveled one end to aid in adequate penetration. |
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To add to the welding advice, I’m planning a dedicated 5.56 can to be done in 17-4. It will have a min walk thickness of .060, for integrity and weld design. I had been playing with pulse settings, and really liked the results. Basically my process is get the speeds and settings satisfactory, start the motor, and hammer the pedal letting the pulse do the fine details. This helps with heat control and makes it so I don’t have to feather as much. I try to make it simple. I haven’t built anything yet as I’m still working on paperwork, but my experimentation on scrap has been promising. |
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A couple things that have been pointed out:
1. Outer diameter and length, of suppressor, along with barrel length and whether you intend to use HV ammo are foremost thoughts. This, along with fire schedule, are the most important factors. 2. Material: 316 is not strong stuff. For corrosion, sure, but not when it comes to suppressors. I'd go 17-4. It's cheaper, stronger, and easier to machine than 316. 3. Designing the baffles to achieve a proper weld fitment is a good idea. I'm not sure if @garred8787 was referring to me, but here's my setup for a tubeless, 17-4 suppressor, dedicated to a 10.3" 5.56mm. The baffle fitment area had a step, as to create a sort of lap joint, w/ a butt fitment. There was no risk of embrittlement, on the inside, due to lack of purge gas. I stepped the wall thickness, w/ the blast being near .07 and the exit close to .04. The overall package is 1.5"OD x 6-1/8"LG |
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Quoted:
A couple things that have been pointed out: 1. Outer diameter and length, of suppressor, along with barrel length and whether you intend to use HV ammo are foremost thoughts. This, along with fire schedule, are the most important factors. 2. Material: 316 is not strong stuff. For corrosion, sure, but not when it comes to suppressors. I'd go 17-4. It's cheaper, stronger, and easier to machine than 316. 3. Designing the baffles to achieve a proper weld fitment is a good idea. I'm not sure if @garred8787 was referring to me, but here's my setup for a tubeless, 17-4 suppressor, dedicated to a 10.3" 5.56mm. The baffle fitment area had a step, as to create a sort of lap joint, w/ a butt fitment. There was no risk of embrittlement, on the inside, due to lack of purge gas. I stepped the wall thickness, w/ the blast being near .07 and the exit close to .04. The overall package is 1.5"OD x 6-1/8"LG The torch was held in a magnetic base with the rods similar to how you setup a dial indicator on a work piece. I may try and find it one of these days if it's not a dead link due to photobucket. |
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Quoted:
The one I had seen was on silencertalk I believe and was two o-ringed pulleys staggered in a V then the same on the other end with two rods to move blocks from one another to increase/decrease the gap if needed for different work length. Then the one end had a pulley/motor on it to I use a 5C indexer I motorized which is clamped to my table. The ground is attached to the table, a 120 lb chunk of 1/2" plate on sawhorses until I finish the interior of my new shop and have room for a permanent table. I dial the in the rotation speed and amperage, but still operate the pedal and torch manually. 
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Quoted: How was grounding achieved? I use a 5C indexer I motorized which is clamped to my table. The ground is attached to the table, a 120 lb chunk of 1/2" plate on sawhorses until I finish the interior of my new shop and have room for a permanent table. I dial the in the rotation speed and amperage, but still operate the pedal and torch manually. https://i.imgur.com/fUsKMv1.jpg 
That's a trick setup there! just goes to show many ways to skin a cat. On a side note, have you ever tried using a gas lens on your torch? When I used to weld stainless a lot it was a night and day difference and it also seemed to help reduce the HAZ size. Looks like you have a #17 torch which is what I had and I used a #8 cup with the lens as I felt going to a larger cup needed more CFH of argon and no gain in shielding. and I take it your getting away with just fusion welding with no issues? |
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Quoted:
Some design details. I will be doing some 2inch diameter pistol cans for sub guns and a 1.75 inch rifle can for a Scar 17 and mk20. They will all be tubeless, welded designs with 60 degree cones nesting into each other and the end caps. The baffles will be spaced anywhere from .300 to .75 in away from each other. What im wondering is whats the minimum thickness on the "wall" of the baffle and where they butt together. Ps, I originally was going to try grade 5 titanium but the cost and possible weld integrity issue decided on a stainless option. |
| It's my first shorty. But it compares pretty well to my full size rifle cans, at least from the shooter's ear. I haven't had the opportunity to have someone else fire it from a different hearing perspective yet. Definitely does what I primarily built it for, which is really tone down the report of an SBR without adding too much length. |
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Quoted:
I built my welded cone K can from 17-4 and it's wall thickness is mostly .045" as machined. 308, 6.5 grendel, .223 no problems so far. 5" long, 1.625 OD, 14 oz. https://i.imgur.com/2uXo4qD.jpg These have about the same wall thickness: 
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