Will a 9" 300 BLK cycle subsonics reliably without a suppressor?

You might have to open up the gas port a touch but getting it to run reliably with sub-sonic ammo without a suppressor should not be terribly difficult.

Why would you run sub-sonic if not using a can, especially for a home defense role?

I was going to suggest something like the Spike’s Tactical Barking Spider, but it looks like you may have it covered with the KX3. I kind of like the way the Barking Spider looks, and it makes me feel good that they market it as a device that creates back pressure (I’m a sucker).

My 16 inch barreled pistol gassed upper runs subs and lightly charged hand loads very reliably with no suppressor. The main issue with a pistol gas system is beating the gun to death with high end supersonic loads. At least this is my experience.

azrocks said:

Because I'd still want to minimize sound pressure levels as much as possible - especially considering the confined spaces inside my home.

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Having shot both Remington 120gr and 220gr green box ammo from my 16 inch 300BO I could hear no difference between the two without a suppressor.

I have a PSA 7.5" upper, with a Shockwave brace kit (buffer tube, buffer, and spring) that has run about 100 rds. of subsonic without an issue. Most were 220 gr. from Octane Munitions. Some were Hornadys. No can here.
I had a guy at the range comment to me that the subs were quieter than the 9s being shot at the same stall just prior.

mcb said:

Having shot both Remington 120gr and 220gr green box ammo from my 16 inch 300BO I could hear no difference between the two without a suppressor.

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I bet the guy or gal beside you would.

kcofohio said:

I bet the guy or gal beside you would.

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My brother standing next to me at the range couldn't. Maybe in a confined space it might make more difference but in an open field sighting in a scope both sounded similarly loud without ear protection.

azrocks said:

If I understand things correctly, the supersonic crack is produced by a pressure wave created by the bullet's path through the air. So I wouldn't be surprised if it wasn't noticed by someone standing behind the crown of your muzzle (I'm assuming that's the case) in an open environment. My feeling is that when you add in reflective walls and tight confines, the situation would be considerably different.

Also, is it possible that with a 16" barrel your subs went supersonic?

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Certainly possible. I have not chrono'ed it in my barrel yet and I am still waiting on my suppressor.

azrocks said:

If I understand things correctly, the supersonic crack is produced by a pressure wave created by the bullet's path through the air. So I wouldn't be surprised if it wasn't noticed by someone standing behind the crown of your muzzle (I'm assuming that's the case) in an open environment. My feeling is that when you add in reflective walls and tight confines, the situation would be considerably different.

Also, is it possible that with a 16" barrel your subs went supersonic?

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Most subs run subsonic from a 16" barrel in my experience. Manufacturers usually design them that way. I've never fired them inside a confined space, so you may be onto something with that logic, but in the open, I can not tell the difference between subs and supers in terms of noise unless a suppressor is in play. With the can, the difference is night and day.

Subs should be a lot quieter than supers with no can. If your not wearing ear protection you can tell big time. Even from heavy loaded to light supers.

I’ve done ladder tests from supers with different powder rates and there is a huge difference in even supers at different charges.

I’d guess I’d the subs were loud there Is an issue with them
1. Not subsonic under your conditions. Lots of variables in that. It’s hard to load a sub that works well in a 10” and a 16” and functions both and all gas lengths reliably. And works from sea level to 7000ft. That actually may be impossible.
2. Powder charge is slow and doesn’t pressure up enough to burn most all the powder before exiting the barrel. Thus throwing a fireball and making extra noise.

I've shot both subs and supers in my 16" barrel with no suppressor and I couldn't really tell any difference shooting them in the yard. And yes the subs were really subs as verified by the cronograph and I shot it with a few different powders. My 7.62x39 with a krink brake is quieter as is my 16" 9mm carbine with no muzzle device. I never tried the blackout with the krink brake but I bet that would be reasonably quiet.

I have pistol AR set up with 9" KAK bbl and gas block. It cycles subs and sonics, factory/handloads with zero issues. The subs are not as loud but maybe that's just my perception as the recoil is a lot less. I live in a state where suppressors will likely never be allowed so I can't comment on performance with a can.