Tips for .223 & .300BLK in my .30 cal can?

[Ryanxia]

So I'm dyin over here waiting for my AAC 762-SDN-6 .30 cal can to get out of NFA jail lol (3/10/16 check cash date). I got it primarily for .300 blackout but I'm also going to see how it does shooting .223 out of it (both calibers on an AR platform).

With those two calibers in mind, any tips you seasoned guys have for getting one or both quiet? (I don't reload btw, a friend will do some .300BLK loads for me but most of what I shoot will be something I can buy).

Any particular factory ammo loads you like?
Any particularly quiet brand of AR buffer/spring?
Any particular adjustable gas block?
Barrel length? I think for a comfortable OAL I'm going to do an 8.5" .300BLK barrel with the 6" can.

Haven't built the .300BLK setup yet, still gotta get to it. I have a Sig M400 SBR lower that I was planning to just rebuild an upper for, but I also have a Crusader SBR lower that is still stripped.

I know there's loads of information out there, I just want to know what you guys think since it will be some first hand knowledge.

 

[ny32182]

.223 is going to be loud regardless. Not really anything you can do about it.

300blk, of course you can go supersonic, or subsonic with very heavy bullets. The latter will be very quiet. The former will be much louder, but still quieter than .223. Subsonics have very limited range compared to supersonic 300blk or especially .223.

As long as you have a closed gas system (DI) rifle, and not a piston that is venting high pressure gas at the gas block, there isn't a whole lot more you can do in terms of rifle setup; it is what it is. DI will be quieter than a piston. Probably by a lot.

You should still wear ear-pro if you are going to be shooting supersonic.

 

[Ryanxia]

Thanks, yeah it will definitely be a DI gun, and subsonic loads.
I know .223 will still be loud but a few friends have said they've been to 3 gun competitions and guys were running factory .223 suppressed and it was hearing safe so thought I'd see who here dabbles and found something that's more quiet than others.

 

[ny32182]

Well... I suppose you CAN, but I wouldn't, much, if you like your hearing... .223 is still loud even when suppressed. I've tried it with a couple different cans, and my ears are ringing after about 5 rounds. I've learned my lesson.

Now once you are about 50 yards away or whatever it is perfectly fine... but as the shooter, I would always wear ear pro shooting .223.

 

[m4a1sof]

Never underestimate how loud the supersonic crack is, even on a .22LR. I always wear ear protection shooting supersonic suppressed. Trying to get subsonic 5.56 to reliably function in an AR platform is a futile exercise. By the time you reduce the powder charge enough to get it subsonic it doesn't have enough energy to reliably cycle the action as well as by that time the terminal ballistics are comparable to a .22LR. That was precisely the reason 300BLK was invented to overcome these shortcomings. On the 300BLK barrel length question, 8.5" is a good length. I know you have already purchased your can as have I, but if I had to it all over I would go with a titanium one. The SS isn't bad with the 8.5" barrel but every ounce counts when your hanging something off the end of the barrel and there only a couple of hundred more bucks.

 

[Ryanxia]

Thanks m4a1sof, as it's been a couple of months since I started this thread I've built my .300BLK with a 8.5" barrel and it does great. Even supersonic .300BLK is pretty quiet, hearing safe for sure. I was never intending to try subsonic .223, I was just wondering about regular .223 which I forgot my 1/2x28 muzzle device at home last time I went to the range to shoot the .300BLK so I still have to test that this weekend.

 

[Theohazard]

Even supersonic .300BLK is pretty quiet, hearing safe for sure.

No, it's not hearing safe. I wish people would stop using the term "hearing safe" to describe any silencer under 140dB. This is a deliberately misleading term that silencer manufacturers use, and it's a misrepresentation of the guidelines for noise exposure. When you fire your 300 Blackout with your SDN-6 and you don't use hearing protection, you're permanently damaging your hearing over time, even with subsonic ammo.

Here are the decibel guidelines for daily exposure as described by the American Hearing Research Foundation (emphasis mine):

"Habitual exposure to noise above 85 dB will cause a gradual hearing loss in a significant number of individuals, and louder noises will accelerate this damage. For unprotected ears, the allowed exposure time decreases by one half for each 5 dB increase in the average noise level. For instance, exposure is limited to 8 hours per day at 90 dB, 4 hours per day at 95 dB, and 2 hours per day at 100 dB. The highest permissible noise exposure for the unprotected ear is 115 dB for 15 minutes per day. Any noise above 140 dB is not permitted.
[...]
Combined use [of ear plugs and muffs] should be considered when noise exceeds 105 dB. Note that for such situations, it may be that there is no type of hearing protection that will stop a very loud noise from affecting you."

http://american-hearing.org/disorders/noise-induced-hearing-loss/

Just for reference, a centerfire rifle with a silencer is usually in the 135 - 140 dB range. A pistol with a silencer and subsonic ammo is usually in the 125 - 130 dB range. And a .22 with a silencer and subsonic ammo is usually in the 115 - 120 dB range.

Even the quietest 7.62 cans shooting 300 Blackout run about 125 dB for subsonic ammo and around 135 dB for supersonic ammo. For comparison, a chainsaw is about 110 dB and a jackhammer is about 130 dB. Now, the short duration of suppressed gunfire means its damage level doesn't directly correspond to a sustain noise like you get with power tools, but it's clear that suppressed firearms aren't medically "hearing safe".

 

[Ryanxia]

Good point Theohazard. You're right the term hearing safe is the term popularly used to describe shooting at a comfortable level without hearing protection.
The majority of people I know including myself don't put on hearing protection to run a chainsaw or go to a rock concert so I guess it is what it is for us. But I agree with your statement and will try not to use hearing safe again when describing the personal comfort noise level of my shooting.

 

[rscalzo]

The majority of people I know including myself don't put on hearing protection to run a chainsaw or go to a rock concert so I guess it is what it is for us...then years later you wind up with tinnitus. The doctor's will simply tell you there is nothing they can do and you hope you'll get used to the constant ringing.

As far as hearing safe even for the subsonic 300 BLK loads, you better hope no one else is shooting something supersonic and LOUD.

Far better to take precautions now. Wish I did. Indoors I stress double ear protection for students. Better late thabn never I use ear protection for leaf blowers and lawn equipment. Event ditched the load pipes on the bike.