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 Post subject: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Wed Oct 31, 2012 11:32 am 
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The owner's manuals for the Beretta A390, A391, A400, and A300 Outlander all say that the gas piston should be inserted into the gas cylinder before the barrel is installed on the receiver. Most people I know do not do that with the 390/3901/391 - we usually drop the piston onto the shaft of the magazine cap and then put the barrel on, letting the gas cylinder come down over the piston. I am not aware of any problem caused by that assembly process, but I guess Beretta had some reason for their instructions. However, I did recently see a problem with assembling an A400 that way, and I'm sure the same problem can arise with the A300 Outlander.

The owner's manuals for the A400 and A300 Outlander say:

CAUTION: In order to prevent damage to the elastic piston seal, first insert the
piston into the chamber cylinder and then insert the magazine tube shaft through
the piston hole.


The "elastic piston seal" functions very much like a piston ring in a reciprocating engine. It is a split metal ring that is compressed to allow it to enter the cylinder, where it rubs the inside of the cylinder wall while the piston moves up and down. Below is an illustration from the A300 Outlander owner's manual, showing the seal (ring) being compressed so it will go into the cylinder:
Image

In the case I saw, when the shooter tried to fire the first shot of the day from his A400, it would not go off. Upon examination, we found that the bolt was not closing completely. When we pulled the barrel off, we found that the piston would not go all the way into the cylinder, because one end of the ring had been pulled out of the piston groove that it is supposed to ride in, and was hitting the end of the cylinder, keeping the piston from going in and keeping the action from closing all the way. When we pushed the end of the ring, it slipped into the groove, and it was then possible to compress the ring and insert the piston into the cylinder. We did not notice any obvious damage.

The shooter had attempted to assemble the gun the way he had always done his 391 - just dropped the piston onto the shaft, then put the barrel on. That simply doesn't work with the A400 and A300 Outlander the way it does with the other models in the 300 series. Although there didn't appear to be any damage in this case, I'm sure it would be possible to damage the ring, and maybe the piston and cylinder, by trying to assemble them that way.



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"Beretta 391 Disassembly" - What the owner's manual doesn't tell you. See: viewtopic.php?t=123733
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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Wed Oct 31, 2012 3:34 pm 
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Joined: Wed Oct 05, 2011 12:41 pm
Posts: 78
I have seen many, many, many A400 piston rings get damaged this way. When you usually bend them out of shape, you usually can't bend them back into shape and have them seal correctly. If anyone does do it and damages a ring, Brownells does carry them.


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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Wed Oct 31, 2012 8:24 pm 
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Thanks for the heads up. murf


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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Thu Nov 01, 2012 12:17 am 
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Good to know. Good catch.


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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Thu Nov 01, 2012 11:02 am 
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Anyone know of a easy way to remove the ring from piston -- I had a quick go at it but it looked like it had to be opened up quite a bit to slide off piston and didn't want to break it. ?

This was over the square bit at front

The hand book was very specific about putting piston in barrel first.

dave

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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Fri Nov 02, 2012 9:12 pm 
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I install the gas piston into the barrel, then install the barrel into the reciever, I always did it this way too on my 391, and thats how I continue to do it on my A400, I haven't had any problems.

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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Fri Nov 02, 2012 9:32 pm 
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DSPUK wrote:
Anyone know of a easy way to remove the ring from piston -- I had a quick go at it but it looked like it had to be opened up quite a bit to slide off piston and didn't want to break it. ?

This was over the square bit at front

The hand book was very specific about putting piston in barrel first.

dave


I leave it on and spray with solvent and clean it with a brass brush. If you really want it clean let it soak in a jar of solvent over night. It's just going to get dirty again so I wouldn't get to fussy. :)


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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Mon Jan 07, 2013 4:02 am 
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Thanks for this write-up ... good to know when getting the new gun this week.

Last thing I want is to take this out to the range and it mess up cause of an error like this.

I will watch for this when putting it together this week.


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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Mon Jan 07, 2013 9:30 am 
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Joined: Tue Mar 02, 2010 10:53 am
Posts: 183
Location: MA's North Shore
Top o'the morning to you Seamus,
And a tip o'the hat for the warning. The same thing happened to a new xcel at my club just yesterday. The fellow bought the gun Friday, shot a skeet round on Saturday yet on Sunday (after re-assembling the gun, evidently contrary to the manual) bent the "piston ring", couldn't fire the gun (as you described, the bolt wouldn't fully seat) and only after disassembly found the error.
Great gun yet like all of 'em, a little mechanical attention is necessary.
O'Wooster


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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Fri Sep 06, 2013 5:13 pm 
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Joined: Fri Apr 02, 2004 9:33 am
Posts: 141
Location: Central Wisconsin
Ugh... always good to find this out... too late :)

First time I cleaned my new but used 32" sporting, that part of the piston had stayed in the cylinder on its own, and I didn't mess with it.

Today when I cleaned the gun, noticed that part of the piston assembly still on the shaft on the mag tube.

Cleaned it up a little, and left it right there, put the barrel back on, and let the bolt slam home.... and now the ring is bent...

well. you live, you learn :) and of course, Brownells is out of stock at the moment.

EDIT seeing how mine may just be bent, i bent it back, reassembled... will have to see if firearm is operational.

i do intend to try and to pick up spares


Last edited by Carphunter on Fri Sep 06, 2013 7:16 pm, edited 1 time in total.

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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Fri Sep 06, 2013 5:30 pm 
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new to the A400 - Is the piston ring an item that you ought to keep a spare around? I was thinking that and maybe an end cap?

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 Post subject: Re: CAUTION: A400/A300 Installing the Barrel and Piston
PostPosted: Sun Sep 08, 2013 7:21 pm 
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Don't the Xtremas have that ring on the piston?




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