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Discussion Starter #1 (Edited)
Well, I got my Turner Fabrications MP5 clone out today and mounted up my Liberty Mystic suppressor using a Gemtech Multimount 3-lug adapter mount. I've been looking forward to this configuration for a long time...

I have to say: I was entirely unimpressed with the suppression level. I could not shoot the firearm without hearing protection.

On the other hand: I typically run this suppressor (minus the Gemtech mount of couse) threaded on my 9mm AR15 SBR and it is scary quiet on that platform. So much so, that I get so many people asking about the suppressor at the range, that now I just hand out business cards for a local dealer and let him answer all the questions. It is suppressed .22LR quiet. No kidding. You hear the bullet slap the paper louder than the rifle firing.

I shot supersonic ammo, 119-grain, and not specifically subsonic ammo 147-grain, same as in my AR15.


That begs the question: What's the deal? Is the HK94/MP5 platform simply not suppressable to a reasonable level unless you shroud the whole barrel and front of the receiver like an MP5SD?


(Oh, and the Turner f-ing ROCKS!)
 

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W

I shot supersonic ammo, 119-grain, and not specifically subsonic ammo 147-grain, same as in my AR15.


That begs the question: What's the deal? Is the HK94/MP5 platform simply not suppressable to a reasonable level unless you shroud the whole barrel and front of the receiver like an MP5SD?
Change your locking piece for the change in pressure due to the supressor?
 

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I had the opposite experience with my suppressor. It is loud on the AR 9mm with 5.5 inch barrel because it is pure blowback. On my MP-5K it is very quiet.
I would try some different 147 grain ammo.
 

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Discussion Starter #5
I currently have a RCM 100-degree piece installed. What is the alternative and how would changing the locking piece change the performance of the suppressor? Honest question.
 

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Discussion Starter #6
I had the opposite experience with my suppressor. It is loud on the AR 9mm with 5.5 inch barrel because it is pure blowback. On my MP-5K it is very quiet.
I would try some different 147 grain ammo.
What type of suppressor mount are you using on your HK ? Threaded or 3-lug?
 

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We shot a Liberty Mystic with 147 subsonic with a factory MP5-N and one of my D54P-N's and it was stupid quiet. When we ran out of subsonic and switched to sonic 124-gr the ears had to go back on.
 

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Grand Chazzar
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I got to try the mystic on my k clone ....
Although it is like 2ft long , if I remember correctly it suppressed pretty good.
But I couldn't get over the look of it on the k gun ???
 

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Calling Dr. Physics! <stat>
The locking piece will affect reliable cycling, but really shouldn't affect suppression appreciably. How a can sounds is very much a subjective thing. Two different people will perceive the sound differently and that perception will change depending upon the position of the listener. It will absolutely sound different from the shooter's position as opposed to an observer 5 yards to the left, parallel to the receiver, as opposed to a listener to the right, parallel to the receiver, as opposed to a different observation position. And it simply could perform better with a blow back system, as opposed to a roller system like your clone.

And it could be that the actual dB reduction *is* the same between the clone and your AR! Really! What may have changed is the pitch of the system on a different platform. It may sound "brighter" on your clone than your AR... that means that even though the actual sound pressure reduction is the same, because of the change in pitch (think of a musical instrument), it may sound louder.

One other thing... You said 119gr bullets. Are you really using these or are you using 115gr standard FMJ/TMJ's? If you are comparing 119gr hot loads to 115gr standard loads, you've discovered your culprit! IIRC, many 119's are loaded pretty hot...
 

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Try sub sonic bullets. Also, have someone else shoot the gun.

Right after I put the can on my mp5 clone I was also unimpressed. I was mad because I spent the dough on the gun and it's stamp, the can and it's stamp and a couple other goodies. I was only a little quieter than it was with the fake can on it. As I turned around to express my dissatisfaction to the girl, she looked like Edvard Munch's 'the scream'. She was dumbfounded.

I then handed the gun over to her and proceeded to be amazed.

I think I was hearing all of the action noise now that the actual report was removed, and it sounded just as loud when shooting.
 

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Grand Chazzar
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Try sub sonic bullets. Also, have someone else shoot the gun.

Right after I put the can on my mp5 clone I was also unimpressed. I was mad because I spent the dough on the gun and it's stamp, the can and it's stamp and a couple other goodies. I was only a little quieter than it was with the fake can on it. As I turned around to express my dissatisfaction to the girl, she looked like Edvard Munch's 'the scream'. She was dumbfounded.

I then handed the gun over to her and proceeded to be amazed.

I think I was hearing all of the action noise now that the actual report was removed, and it sounded just as loud when shooting.
+1000
Let someone else shoot & you stand 5 -10 ft away
Makes all the difference in the world
 

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I've got two clones I shoot suppressed with a Gemtech Multimount. With subs, they both sound very quiet and very different than pistol hosts. I should have a Liberty Infiniti within a few weeks and I'm hoping they will sound even quieter. I definitely recommend subsonic ammunition for the best jollies...
 

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I use a Mystic on a 3-lug with my MP5 clone shooting 147 gr subsonic reloads and I'm pleased with how quiet it is. It's quieter to my ears than my 9mm AR15 w/5" TROS 3-lug barrel and the same can.

It's true, though - you can't really appreciate the suppression when you're the one shooting it.
 

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I think that's crap about not being able to appreciate the suppression as the shooter. I have an MK9K for my 3lug needs and it's stupid quiet on the MP5s.

- Shoot subsonic ammo. Depending on how your AR is set up, your ammo may not be going supersonic in the AR but is in the MP5, unlikely but whatever. Don't mess around with shooting supersonic suppressed in 9mm, subs are cheap enough.
- Consider the locking piece. Aside from what someone here incorrectly said, if the MP5 is unlocking before the pressure has come down, the shooter will hear a loud POP at the ejection port. You need the pressure to come down for the reliability of the gun, safety, noise, and reduce wear and tear.
- The Mystic albeit heavy is a decent can and the MP5 suppresses better than the blowback ARs, so don't worry yet, most likely user error.
 

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Pardon me, este, for not posting with sufficient clarity. While the locking piece can, as you pointed out, have some effect on the sound, its main function is to ensure reliable cycling. And while I did not say anything about appreciating the the sound as the shooter, it IS perceived differently, depending on the location of the listener. Since the OP did not mention a popping sound, I assumed that he was just referring to the sound being louder in general.
 

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Discussion Starter #17
We shot a Liberty Mystic with 147 subsonic with a factory MP5-N and one of my D54P-N's and it was stupid quiet. When we ran out of subsonic and switched to sonic 124-gr the ears had to go back on.
Hmmm... Tri-lug mount or threaded barrel mount?

Calling Dr. Physics! <stat>
The locking piece will affect reliable cycling, but really shouldn't affect suppression appreciably. How a can sounds is very much a subjective thing. Two different people will perceive the sound differently and that perception will change depending upon the position of the listener. It will absolutely sound different from the shooter's position as opposed to an observer 5 yards to the left, parallel to the receiver, as opposed to a listener to the right, parallel to the receiver, as opposed to a different observation position. And it simply could perform better with a blow back system, as opposed to a roller system like your clone.

And it could be that the actual dB reduction *is* the same between the clone and your AR! Really! What may have changed is the pitch of the system on a different platform. It may sound "brighter" on your clone than your AR... that means that even though the actual sound pressure reduction is the same, because of the change in pitch (think of a musical instrument), it may sound louder.

One other thing... You said 119gr bullets. Are you really using these or are you using 115gr standard FMJ/TMJ's? If you are comparing 119gr hot loads to 115gr standard loads, you've discovered your culprit! IIRC, many 119's are loaded pretty hot...
I didn't think the locking piece would impact suppression, but being relatively new to the HK platform thank you for the confirmation on that point!

I usually gather my impression of a suppressor's performance by standing to the side while someone else is shooting. I stand parallel with the muzzle and perpindicular to the bore about 7-10 feet away. This is approximately where most manufacturers meter their suppressor performance. Admittedly, my test yesterday was me alone so you could be entirely correct that I was hearing mostly bolt clatter.

I get what you're saying about a brighter sound.

I typoed that grain weight. I meant 115-grain. Sorry about the confusion. 119 would definatly be a +P+ round!

Try sub sonic bullets. Also, have someone else shoot the gun.

Right after I put the can on my mp5 clone I was also unimpressed. I was mad because I spent the dough on the gun and it's stamp, the can and it's stamp and a couple other goodies. I was only a little quieter than it was with the fake can on it. As I turned around to express my dissatisfaction to the girl, she looked like Edvard Munch's 'the scream'. She was dumbfounded.

I then handed the gun over to her and proceeded to be amazed.

I think I was hearing all of the action noise now that the actual report was removed, and it sounded just as loud when shooting.
Yeah, this could be the case. I'll have to bring someone else with when I go again.

Are you using a tri-lug or a threaded barrel mount?
 

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Discussion Starter #18 (Edited)
WOW A whole second page of responses! Thanks fellas!

Ok, so a few things to clarify based on your replies:

- It was only me at the range so I was only behind the sights so to speak and did not have a chance to listen to the side.
- When I do evaluate suppressors, I typically listen from three positions: 1. Behind the sights 2. To the side 5 - 7 feet 3. 45-degree angle behind by 10 feet
- I have 4 suppressors currently and most shooters I know have one or more (in AZ you can now hunt with them so everybody is getting on the bandwagon)
- My background has been the AR15/M16 and bolt rifle platforms. I'm 4-monts new to the roller-lock system
- Outdoor shooting only. Local indoor ranges bitch and moan too much about my SBRs, PWS breaks, and select fire
- I rarely have felt the need to shoot subsonic ammo except in .22LR, because my Mystic and Torch (both Liberty Suppressors) do so well even with supersonics

That being said:

- I'm relatively new to the HK roller-lock concept, so I have no idea of the impact of changing the roller lock timing with different locking pieces, but I 'get' the concept.
- My 9mm AR15 is highly "tweaked". Tungsten filled bolt group. Tungsten recoil buffer. Shortented recoil spring. Internal buffer tube space to shorten the recoil further. "Solid" Hogue forearm that partially covers the suppressor. All intended to slow the ROF and decrease wear on the receiver and quiet the weapon's mechanics in both semi and full auto.
- This it my first experience with a tri-lug mount
- I now have two MP5 clones, an MP5-K clone, and an HK53 clone. I'd like to suppress all of them (well, not the "K") so I'm hoping for better performance with roller locked systems in general

Further questions and tests:

- I'll evaluate from the side next time
- Does a tri-lug mount "leak" air and sound at the base back towards the shooter?
- I'm going to remove my handguard from my AR and see if it is louder with the rear of the suppressor unprotected, exposing the mount vent holes
- What locking piece (currently with a stock 100-degree piece) would delay the release of roller lockup in suppressed mode? Higer angle or lower angle?
- Where can I find more information on the concept and design of the roller lock system to better understand its function?
- Okay, okay, okay... I'll get some subsonic 9mm. It just seems like you're throwing the bullet downrange they're so damn slow! :wink:
 

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Discussion Starter #19
I think that's crap about not being able to appreciate the suppression as the shooter. I have an MK9K for my 3lug needs and it's stupid quiet on the MP5s.

- Consider the locking piece.
I'm currently running a 100-degree locking piece. Which direction does one go for shooting suppressed? Higer or lower?
 

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You need to be running hearing protection even suppressed. Unless you are getting overall noise to less than 90db (you aren't), you are damaging your hearing. Simple facts.
 
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