Planning my first silencer build

[Veggicide]

Ok, I figured out where I was going wrong in my calcs. I was treating the 300 blackout pressure listed as 55000 psi was the pressure in the barrel right before the bullet leaves the barrel as opposed to the peak pressure Anyway, this site* gives some (limited) guidance for what the average pressure will be in the barrel based on the length. With that, a (conservative) estimate of 1/5th the max pressure is what I'll use for the barrel pressure. Results will be delayed...






* http://www.closefocusresearch.com/calcu ... un-systems

[fishman]

Don't bother calculating anything. This is the type of stuff that is best done experimentally. Use everyone else's experience.

Adding to T-Rex's sage advice of 28TPI, here
are the five cut sequence to reach the required .024"
minor diameter:

.007/.006/.004/.004./003

And it is important to set up the compound to ~60º
which means that on the graduated compass you set to 29.5º.

it is not a requirement to thread that way. My cut sequence is more like 5/4/3/2/1/1/1/1...1/0/0/0 and I plunge straight in, not on an angle. I understand the benefit of doing 29.9° but my machine isn't capable and it certainly isn't necessary.

[ECCO Machine]

it is not a requirement to thread that way. My cut sequence is more like 5/4/3/2/1/1/1/1...1/0/0/0 and I plunge straight in, not on an angle. I understand the benefit of doing 29.9° but my machine isn't capable and it certainly isn't necessary.

Yup, everyone develops their own technique based on their equipment and tooling. I use top notch type inserts for external, triangular IR inserts for internal, I plunge straight in, and would typically cut 28 pitch in 4 passes plus a spring pass or two, something like 8/8/6/6/0/0 using sharp point cutters or 8/6/6/4/0 using pitch specific cutters (remember, a sharp cutter will need to go deeper than the thread root depth). After that I follow them with a fine triangle mini file on external, and knock my crests down with 320 grit internal or external.

[garredondojr]

it is not a requirement to thread that way. My cut sequence is more like 5/4/3/2/1/1/1/1...1/0/0/0 and I plunge straight in, not on an angle. I understand the benefit of doing 29.9° but my machine isn't capable and it certainly isn't necessary.

Yup, everyone develops their own technique based on their equipment and tooling. I use top notch type inserts for external, triangular IR inserts for internal, I plunge straight in, and would typically cut 28 pitch in 4 passes plus a spring pass or two, something like 8/8/6/6/0/0 using sharp point cutters or 8/6/6/4/0 using pitch specific cutters (remember, a sharp cutter will need to go deeper than the thread root depth). After that I follow them with a fine triangle mini file on external, and knock my crests down with 320 grit internal or external.

wait so you guys are losing me. Your saying you can single point thread without having to use the compound? as in you just use the cross slide to increase your cuts? this would make life so much easier for me if that is the case.

Thanks, George

PS sorry for the hijack

[T-Rex]

wait so you guys are losing me. Your saying you can single point thread without having to use the compound? as in you just use the cross slide to increase your cuts?

Yes, you can just feed the cross-slide in. When you use the compound, you're cutting w/ the left (spindle) side of the tool. With the cross-slide, the entire front of the bit is used.

[garredondojr]

wait so you guys are losing me. Your saying you can single point thread without having to use the compound? as in you just use the cross slide to increase your cuts?

Yes, you can just feed the cross-slide in. When you use the compound, you're cutting w/ the left (spindle) side of the tool. With the cross-slide, the entire front of the bit is used.

Fantastic! I'm going to give this a try.

So what's the negative in doing this?

one last thing. so say a thread has a .024" height do you just feed in .024" total or is there a little more to it than that?

Thanks again

[fishman]

wait so you guys are losing me. Your saying you can single point thread without having to use the compound? as in you just use the cross slide to increase your cuts?

Yes, you can just feed the cross-slide in. When you use the compound, you're cutting w/ the left (spindle) side of the tool. With the cross-slide, the entire front of the bit is used.

Fantastic! I'm going to give this a try.

So what's the negative in doing this?

one last thing. so say a thread has a .024" height do you just feed in .024" total or is there a little more to it than that?

Thanks again

Like ECCO said, if your tool is a sharp triangle vs a profiled pitch specific tool, it will effect how deep you have to cut to get the same pitch diameter. But for the most part, yes.

[Hard_ware]

wait so you guys are losing me. Your saying you can single point thread without having to use the compound? as in you just use the cross slide to increase your cuts?

Yes, you can just feed the cross-slide in. When you use the compound, you're cutting w/ the left (spindle) side of the tool. With the cross-slide, the entire front of the bit is used.

Fantastic! I'm going to give this a try.

So what's the negative in doing this?

one last thing. so say a thread has a .024" height do you just feed in .024" total or is there a little more to it than that?

Thanks again

Amount of material you can cut given the power of your equipment and tooling.
Cutting both sides going in straight more energy vs leading side at an angle less energy per subsequent passes. But depth of cut, speed, and material are all factors. This is what I have gathered from running a mini lathe.

[Capt. Link.]

Fantastic! I'm going to give this a try.

So what's the negative in doing this?

one last thing. so say a thread has a .024" height do you just feed in .024" total or is there a little more to it than that?

Thanks again

Many lathes can't cut smooth threads using a plunge cut.Machine flex and lack of horsepower are major reasons.When you plunge cut you are at the mercy of the slop in the gearing.When cutting at a angle the slop is all on one side and accuracy is ensured.The other reason is generations of craftsmen would be rolling in their graves and its way to close to the holidays for that.

[Hard_ware]

Fantastic! I'm going to give this a try.

So what's the negative in doing this?

one last thing. so say a thread has a .024" height do you just feed in .024" total or is there a little more to it than that?

Thanks again

Many lathes can't cut smooth threads using a plunge cut.Machine flex and lack of horsepower are major reasons.When you plunge cut you are at the mercy of the slop in the gearing.When cutting at a angle the slop is all on one side and accuracy is ensured.The other reason is generations of craftsmen would be rolling in their graves and its way to close to the holidays for that.

Good point.

[garredondojr]

Well poop....

[T-Rex]

Well poop....

No one is saying you can't do it, but understand the pros and cons. Smaller machines = lighter cuts. A live center will further aid in keeping the work true.
This is a reason for turning the compound to 29.5*, when feeding from it. That 0.5* gives a bit of clearance on the backside, reducing friction, chatter, a cut not true to 60*, etc.

craftsmen would be rolling in their graves and its way to close to the holidays for that.

Not gonna lie, I laughed a bit

[fishman]

Keep your tool sharp and take lighter than typical cuts and you should be fine with a plunge cut. If you can do 29° cuts instead, I would go that route.

[ECCO Machine]

Well poop....

No one is saying you can't do it, but understand the pros and cons. Smaller machines = lighter cuts. A live center will further aid in keeping the work true.
This is a reason for turning the compound to 29.5*, when feeding from it. That 0.5* gives a bit of clearance on the backside, reducing friction, chatter, a cut not true to 60*, etc.

This is important. When I talk about plunging straight in and taking .008" or more at a pass, remember that I'm using NT3 inserts in a 1" holder that's locked down on a CXA size QCTP mounted on a 3 horsepower, 2 ton lathe with a carriage that weighs 5 or 6 times what an entire harbor mini lathe does, and I also run a compound lock to take all movement out of that. This machine can peel off .100" deep cuts (.200" radius reduction) on 1.5" 17-4 round bar at a feed rate of 5 IPM and smile about it.

You're not gonna be able to cut threads like that on a benchtop machine or old Atlas 10F, Southbend 9", etc.

[Veggicide]

Been busy last few days and haven't gotten to do a ton, but I've got some CAD to share....


Couple things to get opinions on. First, on the barrel adapter end you will notice a few features. There is a chamfer on the tube and a reverse on the adapter. This is for keeping them both as concentric as possible when it is fully screwed in. The same can be said for the other end of the barrel adapter where there is a tight fit between it and the tube. All these features can be made in one setup on the lathe, so it should all stay super concentric when assembled. Is this way overkill?

I'm not sure if my blast chamber is big enough or if it needs any special features. I've got 60 degree cones at 1/2" apart. They are about 0.03" thick and there are 9 total. The overall length is about 6.65". Feels kinda short to me. I'm thinking of adding an inch or two to the blast chamber, or maybe spacing out the baffles a bit more. All the critical dim's need to have a second pass once I actually decide on a barrel.

Any comments?

[John A.]

There is no such thing as overkill on this forum. Unless you're just being over the top mad scientist kind of cray cray. And even then, would probably be welcomed

I see no problem with how you are making your final baffle and endcap. I like that actually.

Since you're asking for feedback though, I would make the last cone a little thicker to give that baffle slightly more meat so it will be able to support everything better since it has a couple different cuts where everything joins together. It probably wouldn't have to be twice as thick or anything, but I would beef up that area a little more than the others.

[T-Rex]

You don't have the OD listed, but it looks to scale @ 1.5in. I'd still say a 1.375 x 8 is all you need. Just like a typical 9mm design. This should help drop a bit of weight or at least manage it more efficiently.

Definitely need to thicken the blast baffle. Added weight will be negligible, but strength and erosion protection will be increased. Two things a form 1 builder benefit from. I'd recommend from .07-.1in

If your primary use is subsonic, I'd do spacing similar to: .75,.625,.625,.5,.5,.5,etc. Allowing a bit more room, in the beginning, for gas expansion.

You don't need to do your last 2 baffles that particular way. Keep your 2nd to last baffle as a common and give the last one a washer/disc type shoulder. Similar to the Octane's last baffle

[ECCO Machine]

You don't have the OD listed, but it looks to scale @ 1.5in. I'd still say a 1.375 x 8 is all you need. Just like a typical 9mm design. This should help drop a bit of weight or at least manage it more efficiently.

Definitely need to thicken the blast baffle. Added weight will be negligible, but strength and erosion protection will be increased. Two things a form 1 builder benefit from. I'd recommend from .07-.1in

If your primary use is subsonic, I'd do spacing similar to: .75,.625,.625,.5,.5,.5,etc. Allowing a bit more room, in the beginning, for gas expansion.

You don't need to do your last 2 baffles that particular way. Keep your 2nd to last baffle as a common and give the last one a washer/disc type shoulder. Similar to the Octane's last baffle

While I'd still go 1.5" diameter for rifle, I agree with everything else, and would add:

-Don't counterbore your mount to go back over the barrel. Limits mounting options

-Go 8" overall, add 1 baffle, use the spacing recommended above, put the rest of that length into the blast chamber

-Whether integral or a part of the mounting system, incorporate a brake to make better use of the blast chamber and save wear on your blast baffle.

-Go 65° included on the cones and give them a bit of shoulder, ~.150". I've played with angles from 40° to 75° on rifle cans, and 65° with a .125-.200" shoulder, an aperture .040"-.050" over bullet diameter and an asymmetric radiused clip ~1/2 aperture radius (no clip on blast baffle) gives the best result with supersonic rifle rounds.

[fishman]

You don't need to do your last 2 baffles that particular way. Keep your 2nd to last baffle as a common and give the last one a washer/disc type shoulder. Similar to the Octane's last baffle

+1

You don't have the OD listed, but it looks to scale @ 1.5in. I'd still say a 1.375 x 8 is all you need.

-1 nonsense! Make it 1.625" more bigger is more better! All my cans are 1.625" because apparently I hate having things weight a reasonable amount

Your front endcap looks a lot like the one on my 300blk. Add some milled slots like I did, it will be lighter and you'll have a feature you can use to apply torque to the cap. Weight matters the most at the front end.

Your rear cap could go on a diet as well.

How do you plan to bore your tube that deep? Instead of having a step inside, just use a blast chamber spacer.

6.5" is pretty short. Dont expect it to work wonders. Im not knocking short cans, but have realistic expectations.

[T-Rex]

While I'd still go 1.5" diameter for rifle, I agree with everything else, and would add:
I thought I read it was for a 300blk pistol and mostly for subs?
-Don't counterbore your mount to go back over the barrel. Limits mounting options
Agreed
-Whether integral or a part of the mounting system, incorporate a brake to make better use of the blast chamber and save wear on your blast baffle.
Absolutely. Blast baffle can be spaced off this .25-.5in
-Go 65° included on the cones and give them a bit of shoulder, ~.150". I've played with angles from 40° to 75° on rifle cans, and 65° with a .125-.200" shoulder, an aperture .040"-.050" over bullet diameter and an asymmetric radiused clip ~1/2 aperture radius (no clip on blast baffle) gives the best result with supersonic rifle rounds.
I can't comment on the varying degrees, but the disc/shoulder definitely has shown some reduction improvement.

-1 nonsense! Make it 1.625" more bigger is more better! All my cans are 1.625" because apparently I hate having things weight a reasonable amount
My 1.625x8+in YHM can sounds almost identical to my 1.37x8.625 45OctaneHD. The Octane includes a booster and the bore is for 45cal. Can you go bigger? Absolutely, but why add if you don't need to?
Your rear cap could go on a diet as well.
How do you plan to bore your tube that deep? Instead of having a step inside, just use a blast chamber spacer.
I agree with both of these. You could still to a continuous tube wall or do the reverse and show the step externally. You could keep the tube wall to the thinner dimension and incorporate your blast spacer into the rear mount. This would also allow you to move the rear tube threads forward, to profile the rear mount, and lose even more weight; from both the rear cap and tube length.
6.5" is pretty short. Dont expect it to work wonders. Im not knocking short cans, but have realistic expectations.
Yes

[Veggicide]

There is no such thing as overkill on this forum. Unless you're just being over the top mad scientist kind of cray cray. And even then, would probably be welcomed
Sweet

You don't have the OD listed, but it looks to scale @ 1.5in. I'd still say a 1.375 x 8 is all you need. Just like a typical 9mm design. This should help drop a bit of weight or at least manage it more efficiently.
Correct, 1.5" OD. I'll see what I can do to drop weight

Definitely need to thicken the blast baffle. Added weight will be negligible, but strength and erosion protection will be increased. Two things a form 1 builder benefit from. I'd recommend from .07-.1in
Makes sense. I'm using 17-4 stainless for that baffle. If I incorporate a muzzle brake, is that still needed?

If your primary use is subsonic, I'd do spacing similar to: .75,.625,.625,.5,.5,.5,etc. Allowing a bit more room, in the beginning, for gas expansion.
Sounds good, I'll make this change.

You don't need to do your last 2 baffles that particular way. Keep your 2nd to last baffle as a common and give the last one a washer/disc type shoulder. Similar to the Octane's last baffle
This is a much nicer way of doing the last baffle. I considered threading it to the end cap, but didn't want to do that many threads. This is better, thanks!

-Don't counterbore your mount to go back over the barrel. Limits mounting options
I was thinking this could help with alignment, make the counterbore fit very tight to the barrel. Unnecessary then?

-Go 8" overall, add 1 baffle, use the spacing recommended above, put the rest of that length into the blast chamber
Sounds good.

-Whether integral or a part of the mounting system, incorporate a brake to make better use of the blast chamber and save wear on your blast baffle.
This answered a question I've had since I started looking on this forum, why the brake inside the suppressor? Thanks!

-Go 65° included on the cones and give them a bit of shoulder, ~.150". I've played with angles from 40° to 75° on rifle cans, and 65° with a .125-.200" shoulder, an aperture .040"-.050" over bullet diameter and an asymmetric radiused clip ~1/2 aperture radius (no clip on blast baffle) gives the best result with supersonic rifle rounds.
I'm not quite understanding what you are saying here with the asymmetric clip. Picture?

Your front endcap looks a lot like the one on my 300blk. Add some milled slots like I did, it will be lighter and you'll have a feature you can use to apply torque to the cap. Weight matters the most at the front end.
Planning on it, just didn't model it yet

How do you plan to bore your tube that deep? Instead of having a step inside, just use a blast chamber spacer.
Carefully. I happened to have some TI tubing on hand that was 1.5"OD by .069" wall, so I'm gonna use that and take advantage of the fact that I need a step anyway. I've got some 6" reach boring bars, shouldn't be an issue.

Thanks all for the advice, I'll update CAD tonight or tomorrow and post more pictures.

[T-Rex]

Makes sense. I'm using 17-4 stainless for that baffle. If I incorporate a muzzle brake, is that still needed?
Yes, the heat and particles will still be present in this space. A muzzle brake will greatly reduce the laminar flow and sacrifice itself for the integrity of the blast baffle.
This is a much nicer way of doing the last baffle. I considered threading it to the end cap, but didn't want to do that many threads. This is better, thanks!
You can keep the last baffle's skirt approx. 1/8-1/4in from the inside of the end cap. This will allow you to keep a piece of wipe material held inside. You may never use a wipe, but, if you wanted to, this is an easy feature to incorporate.

[Veggicide]

Makes sense. I'm using 17-4 stainless for that baffle. If I incorporate a muzzle brake, is that still needed?
Yes, the heat and particles will still be present in this space. A muzzle brake will greatly reduce the laminar flow and sacrifice itself for the integrity of the blast baffle.

Sorry, I think I was unclear in my question. Is it still necessary to make the first baffle thicker with a muzzle brake? You maybe were answering that question, just want to be sure you weren't referring to material.

[ECCO Machine]

I'm not quite understanding what you are saying here with the asymmetric clip. Picture?[/color]

Meaning one sided. There are various schools of thought on clipping, but most production cans I've encountered use an asymmetric, and generally a deep radiused cut in rifle cans.

This is one of my Valkyrie/Furtivus baffles before welding the stack:

[T-Rex]

Sorry, I think I was unclear in my question. Is it still necessary to make the first baffle thicker with a muzzle brake? You maybe were answering that question, just want to be sure you weren't referring to material.

Yes, keep the blast baffle thicker, regardless of whether or not a brake is used. The insurance you're buying will weigh more than the negligible amount of material being added.