When something is novel, I like to share it with this forum.  Multiple data deliverables for you today; I have something special to show you.

Conventional wisdom indicates that the suppressed MP5K is louder than the suppressed MP5. That's because it always was, until now.

Sound Signature Review 6.90 - Today we examine the high fidelity test results for the Resilient Suppressors RS9 submachinegun silencer in the subsonic flow regime; subsonic Speer Lawman 147gr 9x19mm ammunition was used in the test, fired from the 8.9-in barrel HK SP5-A2 submachinegun.

The results are interesting. And the really interesting part about them are that the silencer is quieter in the next review:

Sound Signature Review 6.91 - This is Resilient Suppressors RS9 submachinegun silencer in the subsonic flow regime again; same subsonic Speer Lawman 147gr 9x19mm ammunition was used in the test, fired from the 5.8-in barrel HK SP5K-PDW submachinegun.

So, just how hearing safe can an HK MP5 with a subgun silencer? What happens when you go to the MP5-K? Is it louder? Can it ever be quieter?

Yes.

The Resilient Suppressors RS9 is the only 9mm silencer, of which I am aware, that makes an MP5K quieter than a full-size MP5. Review 6.91 contains detailed waveform comparisons. This data was checked multiple ways - it is correct.

This does not happen with other silencers on these guns.

This conclusion flies in the face of everything we thought we knew about the MP5 system, 9mm barrel length, and submachinegun silencer performance, in general. The discovery is so novel that I consider the RS9 to be a significant contribution to the submachinegun suppression state of practice. The implications of this data and analysis are significant. It might end up translating to other hosts and other flow regimes.  I hypothesize that the technology may be duration-limited in some respects; more testing is needed.

For me personally, this changes how I view subgun suppression.

I hope you folks find the data as useful as I did!


Here are the updated PEW Science Rankings.

Resilient Suppressors RS9 9mm HK SP5-A2 Sound Test Results

Resilient Suppressors RS9 9mm HK SP5K-PDW Sound Test Results

Hope you enjoy!

Note: you must use the Resilient direct thread mount to achieve this performance. I did tests to check.

Jay
PEW Science

Chewing through it this morning, very interesting in several areas. The direct thread mount performance vs. another mount showcases the can of worms that is "HUB" mount flexibility- ie what mount was the can developed/tested with and does your choice of mount totally change this? I know @mageever has commented on 3 lug mount performance when comparing a shorter/longer one (I think in regards to Omega 9k) and would love to get him to chime in with perhaps a high level take on it.

This can looks great and I would like to see if Resilient would make a 3 lug mount that could mimic direct thread performance because despite sound advantages I am ride or die with 3 lug on the PCCs.

I own an SP5 and an SD and have had occasional PDW wants to complete the trinity. The PDW performance here certainly doesn't help me in stopping that. I would love to see an SD for comparison sake just to see how modern can development now stacks up against the old guard.

Let me address your points:

1.  The so-called "HUB" mount interface, in my opinion, is one of the sharpest double-edged swords created in the silencer industry.  You can (and will) completely change the performance of some silencers by changing mounts and it is not as simple as a "volume displacement" problem in the blast chamber or even distance to the first baffle, in all cases.  I have done multiple-mount testing of silencers in multiple combustion regimes on multiple weapon systems with multiple barrel lengths, and users are going to be getting different experiences in many cases.  In the case of the RS9 - you will not get the same performance if you don't use their direct thread mount.  Also, you will not get this performance if you put their direct thread mount in a different silencer.

2.  The Omega 9k is a very simple silencer, and therefore, its performance is very predictable.

3.  Regarding Resilient making a 3-lug mount to mimic the performance of their direct-thread mount - I share you desire.  Strongly.

4.  I am thinking of converting one of my SP5 guns to an SD.  (both for the love of the game and for the test host utility).  We'll see.

Thanks for the dialog, as always.

Jay
PEW Science

Your comments reinforce that the sensitivity/resolution of your testing can be VERY host/mount (perhaps even ammo) specific.  Which is why I’m not a member as thus far the only host you use as a test bed that is of high utility to me is the 20” .308.   And that can’t be generalized to other calibers, generally.

Be careful of over-generalizing.

Today we are speaking about relatively low duration, low pressure flow.

Move to your flow regime of interest (20-in supersonic 7.62) and all of a sudden you have scaling applicability for 300WM, etc.

It's not the mounts and hosts as much as it is the silencer technology.

Take a Hyperion or Nomad and go from 308 to 300WM. You're gonna be happier than doing the same thing with a Radiant or Sandman, for example. How do we know this? All of the data and analysis published so far. We can infer certain conclusions based on how we know the silencers work, based on the actual test data. Not perfect, but it's smart.

And if you don't want to support the effort because you are looking to get something out of it personally, that's fine. That's why almost everything I publish is free.

People support PEW Science for the greater good. The effort is grassroots- and so far, it's working.  Thanks for your interest, as always.

Jay
PEW Science

No, Austin, that is not what happened.  The kinematics are verified in the waveforms.  The RS9 traps more flow as uncorking pressure increases, all other things equal.  And the flow rate is higher than typical.

This is the only 9mm silencer I have tested that does this, so far.

The K gun is shorter and the muzzle pressure origin (end cap) is closer to the shooter's head.  Everything matters.

edit:  in fact, you can see this for yourself in a simple way.  Griffin Armament is a PEW Science member company.  As a member of the research cooperative, you can view the waveforms at the shooter's ear.  In section 6.91.1.2, see paragraph 6 which references the phenomenon displayed in Figure 4b.  It's there. I wrote it in words and the waveforms show you what is happening.  Unlocking is way later in time.  This has been verified by Heckler and Koch engineering.  PEW Science roller-delayed blowback data has been internally and externally peer reviewed.

My apologies to those reading who do not have access to the member data, but this is important enough for me to publicly state.

Jay
PEW Science

Agree on the pitfalls of generalization. I doubt I can generalize from the existing reported data set to 8” 300 Blackout supers on a semi host, or 11.5-12.5” mid-gas, tuned-gas 5.56, or 16” mid-gas untuned 5.56, or 12.5” 6.5 Grendel semi.

The shorter k-barrel must be producing a shock wave that hits a sweet spot in that baffle stack with that ammo.  You could branch off a nice design of experiments from this result, though the payout might be uninspiring. .

Yes sir, sometimes extrapolation is difficult.  We do try to push the limits of extrapolation and speculation when we can! hahaha

Regarding the shock physics in the K barrel - I actually don't think it's a mach stem phenomenon.  I believe it to be a flow field phenomenon in which their annular space is more efficiently utilized during the time regime of muzzle pressure being above a certain threshold.  In other words - you exercise more of the silencer in early time with higher pressure, but because the subsonic 9mm cartridge has a relatively low overall combustion duration above a certain pressure, you don't overwhelm the system.

I call it the "goldilocks" subgun silencer hahahahaha - the fact it does it with high flow rate is not only serendipitous for subguns, it's actually mandatory in some ways for the design.  Another thing we might see later is that the RS9 does well on direct-blowback hosts.  I have a feeling the utility of the RS9 is higher than we even think right now.

I'm pretty excited about the data.  The K gun is so fun!  It's neat that it can be quiet!!

Jay
PEW Science

Austin,

The Suppression Rating of the RS9 at the shooter's ear with the K gun is 41.9.  The Suppression Rating of the RS9 at the shooter's ear with the full size gun is 42.5.  They are close.  Really close.  That, alone, should tell you that the RS9 is doing something special on the K gun.  It is almost matching the suppression at the shooter's ear, when it is being used to suppress higher pressure flow and doing it closer to the head.

I hope this helps.....

Jay
PEW Science

To give some frame of comparison, how did the Phoenix do on the SP5K (better, worse, same)? I wonder if its annular features would behave differently based on the muzzle pressure.

No 9mm silencer tested by PEW Science, to date, exhibits increased performance on the K gun compared to the full size gun, except for the Resilient Suppressors RS9.

Today is September 29th, 2022 - for the record.

Jay
PEW Science

Nerds

So I should buy a K gun and RS9?
I really wanted a K in 10 millie

Takes one to know one.

I dunno, 10mm is crazy.

I kinda want a shorty 308 roller gun. You know - for rattling my teeth and stuff.

Jay
PEW Science

How hard would it be to add a metric/score for first round pop for the comparison page?  For hunting and pest animal control that’s a useful figure of merit and particularly relevant to subsonic tests.

Huge +1 to this. On any subsonic caliber FRP is a big deal to me.

Adding a metric and putting it on a page is easy.  Ensuring it is reliable and that people use it correctly.... is another.  I've been giving it some thought. The desire and suggestions from the community do not fall on deaf ears.  Thank you, as always.

Jay
PEW Science

Yeah, characterizing initial, non-steady-state responses in a cohesive way is probably more work having to control for any significant variables if dynamic or confounding interactions are to be accounted for.  A sensitivity study before hand for a few different regimes would be useful.

I was thinking a simple ratio of the integral of the first round impulse versus an average steady state impulse envelope integral might be a good expression of a can’s tendency toward first round pop.  Under the specific test conditions as a qualifier.  An absolute metric for just the first shot starts to lean towards pea under mattress approach rather than including  all data in a ratio.  Just thinking aloud.

Yeah, I tend to mostly agree.

I think a lot about the wiped VOX S test I did. That was a really crazy test. It was 20 shots. I did 20 shots so we could see the system be loud (FRP) then quiet (subsequent shots), then get loud again (as the wipe continued to deteriorate). The waveforms show it gradually occur. The impulse waveforms get grouped in "bins" representing each of those stages. I think I color coded them.

So, when I think about that test, I think about how important it was that the Suppression Rating was still only computed from the first 5 shots, like always. In that way, FRP impacted the rating the most. If I had used all 20 shots, the FRP would have a different contribution.

So, it makes me think about FRP and how important it is and how unimportant it is. Purely, it is important to us. And sometimes just as purely, it is not.

We'll see where it goes!

Jay
PEW Science

Low first round pop has been a big priority for rimfire cans, especially on handguns shooting cheaper, hotter bulk ammo.  Few people recommend a Sparrow anymore as a first or do-all rimfire can.  

On subsonic 9mm that’s another host/caliber where decently quiet levels can be achieved so I think this discussion is relevant, particularly on heavy, roller locked hosts where suppressor length and size are a lessor discriminator and manufacturers have a more open design space.  

For hunters especially first round signature might be the only acoustic metric that matters.

What locking piece was used in the K?

He's running the 80 degree in both K and full size.

Hahahhaa the meme is funny, but you do make a good point haha. There are some factors to consider just presenting one shot like that, but yeah... I understand the sentiment.

Jay
PEW Science