Terrible issue on supressed AR

[wetboyz]

I need some advice please.
My AR is smoking me to death

I am running a NFA 7" upper with a Gemtech m4-02
I have replaced the FA to the one that is a gas port only
I have regulated the gas port
It runs nice but the "smoke" is killing me.

So, the questions are:
1. is there anything else to do to lessen this on the existing platform?
2. If I need to increase the barrel length, should it be 10.5/14.5 or 16- which works best?
3. Other suggestions?

Thank you.

[Bendersquint]

I need some advice please.
My AR is smoking me to death

I am running a NFA 7" upper with a Gemtech m4-02
I have replaced the FA to the one that is a gas port only
I have regulated the gas port
It runs nice but the "smoke" is killing me.

So, the questions are:
1. is there anything else to do to lessen this on the existing platform?
2. If I need to increase the barrel length, should it be 10.5/14.5 or 16- which works best?
3. Other suggestions?

Thank you.

Welcome to suppressed 5.56 shooting, its nasty!

The short barrel is definitely not doing you any favors and aside from masive backpressure its killing your can! Most manufacturers won't warrant anything under 10".

I would do a couple things if I were dealing with this.

Get a longer barrel like a 10-11.5" and see if that helps. The longer the barrel the less the pressures inside the can which translate into less blowback.

Tweak the gas flow(adjustable gas block). If you have one already its not working.

Look into heavier buffers to slo the action and keep it locked a fraction longer, that dwell may be enough to drop that backpressure to more tolerable levels.

[Capt. Link.]

Shooting a MP5SD is no picnic either just learn not to breath.
Have you tried the gas buster charging handle.

[seattlite]

How about wearing a mask: http://respro.com/pollution-masks
http://www.gun-tests.com/performance/feb97lead.html

[wetboyz]

Shooting a MP5SD is no picnic either just learn not to breath.
Have you tried the gas buster charging handle.

Yes good point to both of you.
I have the GB handle and the Pneumatic buffer.
So those two options are already there. It looks like the longer barrel is the key.
I have also been looking at adding this gas block.
http://micromoa.com/

[Capt. Link.]

Shooting a MP5SD is no picnic either just learn not to breath.
Have you tried the gas buster charging handle.

Yes good point to both of you.
I have the GB handle and the Pneumatic buffer.
So those two options are already there. It looks like the longer barrel is the key.
I have also been looking at adding this gas block.
http://micromoa.com/

Honestly the greatest gain would be a different suppressor that featured low back pressure.You may consider a pigtail tube plus a cyclic reducer in addition to the rest.

[eric10mm]

Shooting a MP5SD is no picnic either just learn not to breath.
Have you tried the gas buster charging handle.

Yes good point to both of you.
I have the GB handle and the Pneumatic buffer.
So those two options are already there. It looks like the longer barrel is the key.
I have also been looking at adding this gas block.
http://micromoa.com/

Well that part is a waste of good money. It offers nothing for a semi-only gun.

[Pman5KMO]

I need some advice please.
My AR is smoking me to death

I am running a NFA 7" upper with a Gemtech m4-02
I have replaced the FA to the one that is a gas port only
I have regulated the gas port
It runs nice but the "smoke" is killing me.

So, the questions are:
1. is there anything else to do to lessen this on the existing platform?
2. If I need to increase the barrel length, should it be 10.5/14.5 or 16- which works best?
3. Other suggestions?

Thank you.

Welcome to suppressed 5.56 shooting, its nasty!

The short barrel is definitely not doing you any favors and aside from masive backpressure its killing your can! Most manufacturers won't warrant anything under 10".

I would do a couple things if I were dealing with this.

Get a longer barrel like a 10-11.5" and see if that helps. The longer the barrel the less the pressures inside the can which translate into less blowback.

Tweak the gas flow(adjustable gas block). If you have one already its not working.

Look into heavier buffers to slo the action and keep it locked a fraction longer, that dwell may be enough to drop that backpressure to more tolerable levels.

Actul smoke is mostly lubricant burning. Use a lube with higher smoke point.

A 10.5 and longer barrel will/should have a carbine length gas port. Shorter have pistol ports... means more burning powder blowing back into the action. This means your bolt and action heat up FAR faster with far more gas at higher temp and pressure coming into the receiver.

Personally I wouldn't go shorter 11.3" barrel lengths, the difference in baffle wear even compared to a 10.5" barrel and velocity/range is quite a bit... but still short enough that with a can you are still nice short and not getting too long.

[David Hineline]

Switching to a higher volume 30 cal silencer will have the most effect.

[MicroMOA]

I have also been looking at adding this gas block.
http://micromoa.com/

Thanks for considering my block.
BTW, I do have a few customers using it for 7.5" 556 uppers.
We used the following port sizes:
.0625 for the unsuppressed position
.052 intermediate (for weaker ammo suppressed like PMC or reloads)
.043 for optimal suppressed using milspec ammo - LC M193 or LC M855
Note these were tested to work with a standard power (white Sprinco spring) and H2 buffer.

Some ammo is more gassy than others. PMC seems to be pretty gassy and much weaker than LC. Although the LC is much hotter than the PMC it is not as gassy.
Customers have been been very happy with these port sizes on their 7.5" uppers.

Below is a picture of one setup with our patented gasblock w/ a Silencerco Saker mounted.



Let me know if you have any questions.
Thanks!
http://micromoa.com

[rockman96]

Switching to a higher volume 30 cal silencer will have the most effect.

My thoughts exactly.

[Stout]

I have run an AAC 762SDN-6 on an 8" HK53 with no smoke at all. S&B ammo. Maybe the larger volume is what it takes. Don't have a dedicated 556 can. I've got a video around here somewhere.

http://www.youtube.com/watch?v=Rr_07f0ylp4

[deputyonce]

Also, get a PRI Gasbuster....it will help!

[plumber576]

Try the RTV sealant on the charging handle?

[wetboyz]

Thanks. I will be definitely calling you to discuss this. Do you have any Silencertalk discounts?
So you change your plate recommendations based upon barrel length? The gas port should stay the same.
I am definitely going up in barrel size, its just what I can find in the 11/12/14 range

I have also been looking at adding this gas block.
http://micromoa.com/

Thanks for considering my block.
BTW, I do have a few customers using it for 7.5" 556 uppers.
We used the following port sizes:
.0625 for the unsuppressed position
.052 intermediate (for weaker ammo suppressed like PMC or reloads)
.043 for optimal suppressed using milspec ammo - LC M193 or LC M855
Note these were tested to work with a standard power (white Sprinco spring) and H2 buffer.

Some ammo is more gassy than others. PMC seems to be pretty gassy and much weaker than LC. Although the LC is much hotter than the PMC it is not as gassy.
Customers have been been very happy with these port sizes on their 7.5" uppers.

Below is a picture of one setup with our patented gasblock w/ a Silencerco Saker mounted.



Let me know if you have any questions.
Thanks!
http://micromoa.com

[wetboyz]

[/quote] Actuallly smoke is mostly lubricant burning. Use a lube with higher smoke point. [/quote]

Would you mind discussing the lube issue, with a name please.

[wetboyz]

Try the RTV sealant on the charging handle?

Yes I did. I even went to the Gas Buster Charging handle.

[MicroMOA]

So you change your plate recommendations based upon barrel length? The gas port should stay the same.

Yes, the port in your barrel will stay the same. The Govnah basically gives you movable, replaceable gas ports at any port size you can drill. Unlike other tool less adjustable gas regulation methods out there currently on the market, the Govnah is the only one that uses a standard unmodified gas tube.

New article that just came out this past week explains the background and technical details extremely well here:

Part 1: http://www.recoilweb.com/micromoas-govn ... 38489.html

Part 2: http://www.recoilweb.com/micromoas-govn ... 38639.html