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  The piston can be reversed for suppressed fire, to limit blow back?
GR8TWYT  [Team Member]
3/4/2009 8:59:39 AM EST
Saw this quoted in Silencertalk.com pertaining to POF's - "The piston can be reversed for suppressed fire, to limit blow back." Is this an accurate statement? I have an AAC M42000 ordered for my POF SBR and this piqued my interest.

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okent  [Member]
3/4/2009 3:22:40 PM EST
I have a 9.25 POF and the M4-2000 and I can't say that the reversed piston reduces blowback but you will be happy with the setup.
I would think the suppressed setting would increase blowback due to more restricted flow through the vent holes, but just my guess.

My gun will run with either setting on almost all ammo so I just leave it on the nonsuppressed setting.
It makes way less smoke than any DI gun I have ever shot. I also have a gas buster charging handle but I don't know how much of a difference it makes since I had it for my previous DI setup and haven't shot the POF without it.

Be warned though, the short barrel will have increased erosion of the blast baffle compared to a longer barrel. I have shot about 500+ rounds through this setup and am starting to see some erosion at the aperture, not bad but noticable.
Yours looks like an 11.5" which should lessen the erosion compared to mine.
GR8TWYT  [Team Member]
3/4/2009 3:32:52 PM EST
Originally Posted By okent:
I have a 9.25 POF and the M4-2000 and I can't say that the reversed piston reduces blowback but you will be happy with the setup.
I would think the suppressed setting would increase blowback due to more restricted flow through the vent holes, but just my guess.

My gun will run with either setting on almost all ammo so I just leave it on the nonsuppressed setting.
It makes way less smoke than any DI gun I have ever shot. I also have a gas buster charging handle but I don't know how much of a difference it makes since I had it for my previous DI setup and haven't shot the POF without it.

Be warned though, the short barrel will have increased erosion of the blast baffle compared to a longer barrel. I have shot about 500+ rounds through this setup and am starting to see some erosion at the aperture, not bad but noticable.
Yours looks like an 11.5" which should lessen the erosion compared to mine.


Thanks for the informative response.
Swamp_Rat_Shooter  [Team Member]
3/5/2009 11:30:50 AM EST
the piston system in itself decreases blow back.....well, not really, the piston system keeps the gases out of the upper receiver that would normally come in from the gas tube. the back pressure will still cause some carbon to come into the upper via the barrel itself. the reversible piston is used to control the rate of fire when shooting. by flipping the piston when using a suppressor it reduces the rate of fire, which is normally increased do to the back pressure created from a suppressor. I have found that my suppressed 12.5" POF upper is cleaner shooting with a suppressor then my DI guns are unsuppressed. not to say it is as clean as shooting without a suppressor, there is a noticeable difference when I shoot a suppressor.
sgunn911  [Member]
3/13/2009 4:07:04 PM EST
Originally Posted By GR8TWYT:
Originally Posted By okent:
I have a 9.25 POF and the M4-2000 and I can't say that the reversed piston reduces blowback but you will be happy with the setup.
I would think the suppressed setting would increase blowback due to more restricted flow through the vent holes, but just my guess.

My gun will run with either setting on almost all ammo so I just leave it on the nonsuppressed setting.
It makes way less smoke than any DI gun I have ever shot. I also have a gas buster charging handle but I don't know how much of a difference it makes since I had it for my previous DI setup and haven't shot the POF without it.

Be warned though, the short barrel will have increased erosion of the blast baffle compared to a longer barrel. I have shot about 500+ rounds through this setup and am starting to see some erosion at the aperture, not bad but noticable.
Yours looks like an 11.5" which should lessen the erosion compared to mine.


Thanks for the informative response.



I was told by YHM that my 9.25" was too short to use my suppressor on. Are you saying that I can use it but it will just wear on the suppressor faster? I was worried they said that because somehow the flight of the bullet might be too unstable in a barrel that short and strike or there were issues with the cycling, etc.

Quite a coincidence this was posted as I was just cleaning the piston today on my POF 16" and was looking at the ports wondering the same thing about reversing.
n0zzle  [Member]
3/14/2009 2:51:22 AM EST
Two rings forward for 'normal' use, and one ring (on the piston) forward for suppressed use.
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