Suppressed SBR: 5.56 vs. 9mm

[Riktoven]

This is a question posed out of curiosity, not shopping research since MI does not allow SBRs or Suppressors yet, but I have to ask:

I have seen a lot of people on here asking about suppressing their ARs. Eventually, if MI does allow suppressors I'd like to suppress my P99, and either an AR-15 or a 9mm carbine of some sort.

My question is about ballistics. What is the point of suppressing 5.56 ammunition? Even with softpoints, wouldn't it be more advantageous to be shooting 147gr. subsonic 9mm than a 65-75gr. 5.56 round? If the rounds need to be sub-sonic, softpoints are probably the only good option for 5.56 against 200lb targets (correct me if I'm wrong please), correct?

At 1000fps, is the mass of the projectile the biggest factor in wounding, or does the sectional density play a significant role as well? Basically, what I'm asking is given identical shot placement, does the more expensive 5.56 offer any ballistic advantage over 9mm?

Thanks for replys.

 

[mattf7184]

Who said the rounds need to be subsonic?

Are you looking for an effective fighting tool or just something that is very quiet?

 

[Riktoven]

I'm looking for somthing I can shoot relatively comfortably with NO hearing protection what so ever.

I assumed that meant the rounds had to be subsonic, but my only experience with suppressors is watching a 9mm and .45 pistol shot with subsonic ammunition.

 

[Evil Monkey]

No, rounds do NOT need to be subsonic. You can shoot super sonic rifle rounds like the 5.56mm out of a suppressed rifle and all you should here is the super sonic crack of the bullet as it leaves the barrel, but no BOOM from the escaping gases.

 

[Riktoven]

How bad is that supersonic crack on the old eardrums?

 

[Zak Smith]

I would not recommend shooting a large number of suppressed full-power 556 rounds without earpro. Eventually it will cause hearing damage.

The other thing to think about is gas and "crud" blowback.

With a 9mm AR-15 upper, the breech is not locked, and it operates by direct blowback. In my experience, even a non-suppressed 9mm throws quite a bit back in your face. I strongly dislike shooting a suppressed 9x19 AR-15 upper because of the extreme blastback.

Even with a regular suppressed AR-15, a lot of gas does come back in your face. Illustrated:

[ link to LARGER image ]
[ link to LARGER image ]


Now as far as the pistol goes, I have shot a lot of rounds through an EVO-9 suppressor on a Glock 19, and I can strongly recommend this combination. With subsonic ammo, it is very quiet, and can be shot extensively without earpro. Maybe 5-10% of the time I get some crud blown back into my face. With any of these, eyepro is mandatory.

[ link to LARGER image ]

 

[Riktoven]

I wouldn't be plinking without hearing protection, but I want to be able to grab a gun and go if I had to without my muffs or plugs. The only time I've ever shot without hearing protection was about 60 rounds of 5.56, and that is an experience I never want to repeat (I'm down to about 70% hearing in both ears now, and I blame those 60 rounds for that).

If I were goning to suppress an AR it would be in 5.56.

If I were to go the 9mm route, it would likely be one of Vector Arms creations.

The P99 suppressed would just be to satisfy the twisted James Bond fan inside me.

Ballistically I would definatley prefer full house 5.56, but having never heard this suppressed before I have no idea what to expect. Anyone out there with a suppressed 5.56 and a suppressed 9mm and a decibel meter than can break down the math for me? How many decibels does that supersonic crack have?

Any recomended sites for reasearch on the subject?

Edited to add: GREAT pics Zak...your face looks like mine after one mag through a Steyr AUG.

 

[Zak Smith]

If you've been in a percussion section, I would rate a suppressed 12" SBR firing XM193 about the same as a strong cymbal hit. The sound itself is more like a tire being pierced with a large knife.

I think you get more sound back through the action of the AR than you get from the supersonic crack, which actually travels normal to the bullet path. I say this because my SBR is louder than my suppressed 308-- both fire supresonic ammo at about the same velocity.

 

[Riktoven]

bump

 

[Lucky]

(jealously)
http://guns.connect.fi/rs/index.html

http://guns.connect.fi/rs/trial1999.html

http://guns.connect.fi/rs/dirdiagr.html

 

[ny32182]

My entire experience with suppressed weapons was spending one afternoon at the silencertests.com sponsored shoot in GA earlier this year. That said, there was a LOT of shooting going on, and it was ALL suppressed. Just about any kind of weapon you can imagine was there.

I didn't wear any hearing protection all afternoon. Standing about 10 yards from a suppressed AR being fired was not uncomfortable. The supersonic crack is not painful at all.

The two times I became uncomfortable without hearing protection:

-I fired 60 fairly quick rounds from a suppressed AR-15. I shoot left handed. By the time 60 had been expended, my right ear was ringing slightly. My left ear was totally fine. I wouldn't want to go a whole afternoon shooting that setup with no muffs, but it would sure beat the hell out of unsuppressed if you had to grab the rifle for, say, home defense. I wouldn't worry about any sort of permanent damage in such a situation. Overall, I would rate the noise level as pretty similar to an unsuppressed 10/22, but with a little more downrange supersonic crack.

-Standing close to SBR suppressed AK's was getting uncomfortable. Those were, of course, not near as loud as unsuppressed, but the level of reduction in my estimation was not as good as it was on the AR's, overall. Obviously there are a lot of factors at play, but that was my overall observation on one platform vs. the other.

As I'm sure you observed, the pistols with subsonic ammo are very quiet.

Zak, one quick question: I can't quite tell from the photo. Were you using a Gasbuster CH on the AR in that picture? Thanks.

 

[Zak Smith]

I have used GB and regular CH's, and really can't tell much difference. Gas is going to escape out the rear of the action, and redirecting it slightly will not change the overall situation.