1.5" vs 1.375" OD 9mm

[3strucking]

Looking at designs for a 9mm suppressor for a SBR 9mm AR. Would a larger diameter offer a performance advantage?

[John A.]

Based on volume/area alone, yes.

Granted if the wall thickness isn't so much thicker that it's the same interior diameter.

Interior diameter is what you'd need to look at.

Plus, if it's 1.5" od, it's probably going to be about 1.37'ish inside diameter, and would be less machine time turning it down to the correct specs to fit inside of the tube.

[curtistactical]

We use 1.375 and 1.5 for our integral 9mm cans on AR's, Scorpions, and MPX's. Sometimes the handguard size the customer wants to use negates us using the 1.375 suppressor. The 1.5 suppressors give a more pleasant tone but Db wise both are the same. We get 2 extra k baffles in the smaller tube which I think makes up for some of the volume.

[John A.]

Joe, I'm not sure if you've ever had the chance, but if you can use a tube that barely fits inside of an AR handguard (the older 1.75" ID tubes-not these new lightweight low profile things) on AR9 integrals, you may be surprised at how good it sounds.

The one that I made, I actually USED the AR freefloat handguard as the body and made an endcap for it. Somewhat of a Delisle throwback, only not offset like the delisle.

By far, the most quiet 9mm suppressor that I've ever heard. But to be fair, it's 1.75" ID and 12" long, plus including the ported reflex chamber, there's a lot that can be done in that amount of space.

I know you couldn't do that with the scorpion because the handguard is barely more than 1.5" ID, and I'm not even sure what the sig handguard specs are.

[fishman]

The 45 cal integral he did for me is 1.625".
It barely fits inside the two handguards I use and it sounds great.

[John A.]

I'm pretty convinced a good integral beats any sort of thread on can out there.

I have several threaded holes on the handguard/tube so I could mount several rails. One for a front sight, a side rail and a bottom rail.

At one time, I had the upper on my SBR and used a vertical grip, but got tired of switching everything out when I wanted to use another caliber, so I built a dedicated pistol lower for it now.

Surprisingly, it takes a lot of shots to heat up to the point that it's uncomfortable with the AFG. I think mostly due to the fact that the bottom rail is positioned over the reflex chamber and not over the baffles, so it takes more to heat it up near where your hand is.

Though admittedly, there was never a problem with heat when it was on my SBR and I was using a standard front grip. You could shoot all evening without your hand or fingers getting the slightest bit warm.

[oregon123]

Hello,
New member here! I have been pouring over all of the info on this forum, and believe me there is a TON of info!!! I hate to say this but almost too much lololol.
I too am building an SBR 9mm with a 5.5 barrel and would like to suppress it.
My question is, I was considering 1.5 O.D. 1.370 I.D. stainless tube and was wondering what you threaded the I.D. too? Do you thread to 1-7/16x28 UN? that would only leaves only .031 thickness left, is that enough? Or do you use a proprietary thread combo?
Thanks for any and all info!

[fishman]

I use non-fractional thread sizes.

[oregon123]

Ahh ok. I was scratching my head a little. How
Much wall thickness at the thread area do you recommend ?

[T-Rex]

Just use your Tube ID as the Female thread Dmin. Cutting a 1/28 TPI, using a V-thread tool with no radius, you'll have a root wall thickness of ~.041. Make the female threads a tad longer than the male and there's no need for an internal thread relief cut. This will be fine, especially for 9mm. Others have used tubes with walls thinner than that, for centerfire rifle cartridges.

[fishman]

^ yeah that

I just found my notes for my titanium 1.625" tubes. I bore my tube ID from 1.495 to 1.5", then I use 1.519x28 threads

[Capt. Link.]

Tubing is rarely perfectly round. A skim cut will true up the thread bed plus recessing the threads will prevent you from dragging baffles over them later.

Why the necropsy .....I thought lost souls were posting again.

A 1.375" SS tube would do the deed.A titanium tube would be lighter.A integral would be better.

[oregon123]

Thanks all for the information! I’m still stuck on stainless vs titanium. This can will only be used for 9mm pretty much a dedicated suppressor for one gun. I’m thinking an over the barrel design.

[fishman]

Over the barrel designs are great, especially on blowback carbines.

Definitely do titanium unless you want to use it heavily on a 300 blackout or on full auto.

[oregon123]

It will most likely be only 9mm. I have never machined titanium. What is that stuff like to turn internal threads? Is the stainless strong enough or is this just a weight issue?

[ECCO Machine]

It will most likely be only 9mm. I have never machined titanium. What is that stuff like to turn internal threads? Is the stainless strong enough or is this just a weight issue?

Gr. 9 CWSR Ti tubing is quite a bit stronger than seamless 304 or 316.

Tensile Yield Strength

304: 31 KSI
316: 35 KSI
Gr. 9 Annealed: 72 KSI
Gr. 9 CWSR: 105 KSI


It's also 40% lighter material.

Single point threading is easy with any good, sharp tooling, be it ground bits or fresh carbide inserts. Just don't try to tap it without the right taps.

[Capt. Link.]

You are willing to reflex the tube over the barrel so why not port the barrel and take advantage of a integral design.The overall length will be shorter and the sound better.

[fishman]

Titanium is easy to single point thread

[oregon123]

It will most likely be only 9mm. I have never machined titanium. What is that stuff like to turn internal threads? Is the stainless strong enough or is this just a weight issue?

Gr. 9 CWSR Ti tubing is quite a bit stronger than seamless 304 or 316.

Tensile Yield Strength

304: 31 KSI
316: 35 KSI
Gr. 9 Annealed: 72 KSI
Gr. 9 CWSR: 105 KSI


It's also 40% lighter material.

Single point threading is easy with any good, sharp tooling, be it ground bits or fresh carbide inserts. Just don't try to tap it without the right taps.

So your getting annealed titanium machining it. Then heat treating it!! What is the heat treatment process??

[ECCO Machine]

So your getting annealed titanium machining it. Then heat treating it!! What is the heat treatment process??

No. Tempering Ti is not something any small operation can easily do in-house. I buy CWSR temper tube.

[oregon123]

CWSR , I’ll look it up. The biggest diameter I can put though my late is 1-1/2. I can almost put 1-5/8 it’s close but just shy of it so 1-1/2” it is!!

[ECCO Machine]

CWSR , I’ll look it up. The biggest diameter I can put though my late is 1-1/2. I can almost put 1-5/8 it’s close but just shy of it so 1-1/2” it is!!

https://www.tigertitanium.com/storek/Tube/3Al-2.5V

[fishman]

CWSR , I’ll look it up. The biggest diameter I can put though my late is 1-1/2. I can almost put 1-5/8 it’s close but just shy of it so 1-1/2” it is!!

So just use a steady rest