Advice plz: 5.56 end cap hole size, engraving location

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HotGas
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Advice plz: 5.56 end cap hole size, engraving location

Post by HotGas » Wed Jul 08, 2020 10:19 pm

I've scoured this wonderful place and its many posts, and have not been able to find definitive answers to 2 questions. Kindly forgive me if I've missed existing answers - I only seek the wisdom of those who have vastly more experience than me!

1. As I await approval of my Form 1, I wonder about the hole I will have to drill in the end cap. (20-inch barrel, typical Chinese aluminum monocore "solvent trap," 1/2-28, 6-inch length, 1.358" OD, 5.56 cal. I know it's low-end, but I'm taking it easy my first time out.)

Some go with 9/32" in the end cap. Some prefer 5/16". For 5.56 cal, is there a "sweet spot" sized-hole where suppressor functionality is high and baffle (or end cap) strikes are unlikely?

2. What is the optimal location for the required engraving as far as metal fatigue and strength? The end cap is, obviously, much thicker than the thin-walled aluminum tube. Thicker is better for resistance to explosive gasses. But it seems like the end cap might be exposed to the most brutal gasses, which could possibly make it a poor choice for engraving.

And if the tube is the optimal engraving spot, then what's the best position on the tube? The middle seems weakest to me. If a tube end is better, then which end would be optimal - barrel-adjacent or end-cap adjacent?

I apologize for being OCD. But my father built rocket engines way back in the day, and he used to say: "When other guys have a bad day at work, it's just a bad day at work. When I have a bad day, s--t blows up and people die."

Many thanks!

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T-Rex
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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by T-Rex » Thu Jul 09, 2020 8:16 am

A Chinese, Aluminum, monocore is a horrible choice, horrible. Regardless of your first go'round, don't do it.

Exit bore relies on design, but stay >.080in over caliber.

You can engrave whatever you want. Some do endcap, some the mount, most do the tube. Placement on tube near midle or closer to mount, preferred.
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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by 748 » Thu Jul 09, 2020 10:47 pm

I engraved the tube on my cheap chicom 22lr can.
So much has changed since my last form 1

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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by Ridge Runner » Fri Jul 10, 2020 1:46 am

You need to verify alignment. If you have total indicated runout of less than 0.01" (0.005" misalignment) at the endcap and your endcap hole is actually centered you might get away with boring 0.28" but that is a snug fit. I would consider 5/16".

You also need to inspect the thread fit. If your threads are a bit loose and even if your runout when securely mounted on the host is dead nuts zero having the silencer just a quarter turn loose on the threads can introduce about a 0.1" misalignment at the discharge end of a 6" can. That misalignment will cause a baffle strike unless your through holes are 0.2" over caliber or roughly 7/16' for a .223. You won't want to drill for that. You will want to use a proper crush washer but even with a crush washer loose threads can misalign horribly on a loose fitting thread.

I put a mandrel in my tube and stamped it near the threaded end but your marking location should suit your style.

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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by HotGas » Fri Jul 10, 2020 5:09 pm

Ridge Runner: Excellent advice. I had not given serious enough consideration to the necessity for a tight fit. I'm thinking a proper crush washer and a wee bit of Loctite will be in order. (Unless Loctite has a downside I haven't thought of.) And in the interest of safety, 5/16" is an easy decision. I doubt I'll lose much in the way of functionality, and anyway this first suppressor is mostly about fun and experimentation.

Also, I'm warming to your idea of stamping instead of engraving. I had planned to pay someone for laser engraving - but why bother if this can is, in essence, disposable? A stamp set is 12 bucks on Amazon. When I'm ready for a serious suppressor, I can pay someone for pretty engraving.

(And to those who compare these ChiCom cans to garbage, I hear you. My first car was a Volkswagen beater I literally ran into the ground. When it finally died, I didn't care - it had served its purpose. My next car was a '66 fastback Mustang with a 3/4 race cam 289, 4 barrel Holley carb and Hurst Competition Plus Shifter. You know, a REAL car.)

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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by Capt. Link. » Sat Jul 11, 2020 2:13 pm

Aluminum is a hazard with the peak pressures a 5.56 will reach.This is more about the tube not the core. Aluminum stress fatigue is well known and unforgiving in failure. A well designed tube and baffle system could out live you while poor material choice could fail at any time.

I'm shocked at the bore sizes being recommended. Bore clearance should be as tight as the design will allow.
Plain cone type baffles can be tight because of the lack of asymmetrical flow.I've done .040 in a 8.00" screw on can others have also. A size of .060 has been good for K type baffles and I have seen a few asymmetric that needed over .080. These clearances are derived from the instability caused by the baffles the host plus bullet wiggle caused by bore pressure.

You have the materials for a .22 RF suppressor not a centerfire.
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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by 748 » Sat Jul 11, 2020 6:01 pm

Quiet bore dot com says their aluminum 30 cal solvent trap has been form 1ed and put on up to 300 win mag.
Don't know how long it will last on 300 mag.
So much has changed since my last form 1

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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by Capt. Link. » Sun Jul 12, 2020 11:47 am

748 wrote:
Sat Jul 11, 2020 6:01 pm
Quiet bore dot com says their aluminum 30 cal solvent trap has been form 1ed and put on up to 300 win mag.
Don't know how long it will last on 300 mag.
This federally approved containment vessel was not rated for 300wm.
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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by YugoRPK » Sat Jul 18, 2020 9:15 am

Quiet bores 30 call kit is 304 SS . . You can build one out of aluminum . If it is using fully skirted steel cones it will hold up fine.
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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by bwp777 » Thu Jul 23, 2020 5:59 pm

There is NO way I would take a chance and several months of waiting on an aluminum tube for 556 sir. I'm no expert but I do remember seeing a Huntertown Arms can split and it is steel. I have 2 of em, and they work amazingly well thanks to Curtis Tactical. With that said, it's your money, time and health so just make sure you do some video when it all comes together, or flies apart!!

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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by mcrump » Mon Jul 27, 2020 9:42 am

T-Rex wrote:
Thu Jul 09, 2020 8:16 am
A Chinese, Aluminum, monocore is a horrible choice, horrible. Regardless of your first go'round, don't do it.

Exit bore relies on design, but stay >.080in over caliber.

You can engrave whatever you want. Some do endcap, some the mount, most do the tube. Placement on tube near midle or closer to mount, preferred.
If you have precision equipment then .060 over bullet diameter works best. The .080 gives you a little wiggle room if you are using a drill press.
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Re: Advice plz: 5.56 end cap hole size, engraving location

Post by T-Rex » Tue Jul 28, 2020 7:39 am

mcrump wrote:
Mon Jul 27, 2020 9:42 am
T-Rex wrote:
Thu Jul 09, 2020 8:16 am
A Chinese, Aluminum, monocore is a horrible choice, horrible. Regardless of your first go'round, don't do it.

Exit bore relies on design, but stay >.080in over caliber.

You can engrave whatever you want. Some do endcap, some the mount, most do the tube. Placement on tube near midle or closer to mount, preferred.
If you have precision equipment then .060 over bullet diameter works best. The .080 gives you a little wiggle room if you are using a drill press.
Unless someone specifically mentions or I can decipher from their post that they have machining equipment, I always assume they're using substandard equipment. Hence the >.080" recommendation. If they want a more detailed explanation, there are plenty of threads they can search for.
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