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POF Ejection Problems


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A friend has a POF upper and barrel in .308 It ejects a spent case, just out of the chamber and in the first hundred rounds, I chalked it up to break in. Now it's almost every other round does not eject fully and the bolt slams the next round sideways and literally bend the bullet. The spent case has not fully come out and is stuck at the front of the port. After that first day, I have not cleaned it for about 200 rounds. This is very disappointing when trying to have some enjoyable range time.

Anyone else have POF ejection problems? I could not find much POF info here.

My DPMS was run through the same regimen and throws spent cases about 8 feet. This POF kinda dribbles the spent case onto the table. Is this the difference between direct impingement and a piston action?

If there is another thread discussing this, let me know where it is please.

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 Short stroking , Ejector & or an extractor issue . Piston systems normally don't have short stroking issues unless they have an adj. Piston system & its not adj. properly , they can also get fouled up with dirty ammo . 

  Disassemble Bolt components & clean & inspect , also the Piston assembly , most Piston systems are hard Chrome coated & require NO lubricants , they just help to foul them up when burnt in .

 Does the bolt lock back on last round on a POF ? If its supposed to , see if it does , if its supposed to & doesn't , its short on Gas to cycle the BCG .

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4 hours ago, survivalshop said:

 Short stroking , Ejector & or an extractor issue . Piston systems normally don't have short stroking issues unless they have an adj. Piston system & its not adj. properly 

Tell that to my P716! intermittently on all settings.............

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5 minutes ago, survivalshop said:

 Its fixable .  Do you believe its short stroking ?

Yes, fails to lock back just not everytime, turn up the gas and it will go a bit longer but eventually does it again. If it is fixable Sig hasn't figured it out yet. It can have better than a 100 trouble free rounds then throw fits, clean or not, no broken springs, nothing visible to me anyway.

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13 minutes ago, survivalshop said:

   Have you ever had the complete Piston assembly off the Barrel , piston Block included ?

  Does the cyclic rate of the Action seem slower when this failure occurs , that you can tell ?


Not the block but SIG has. Swapped it and the piston.  Changed the BCG as well. I don't notice a difference, just a click or even a dead trigger once in awhile. All ammo types have seen issues with this rifle, then it will turn around and run a hundred rounds of perfecta without a problem, go figure. I may give them one more crack at it, love shooting it suppressed when it runs. After that it will be sold and I will build a pistol 308.

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These all sound like what I am experiencing. Bolt does lock back every time. Spent shell casings literally would fall into a bowl, next to the rifle. It is suppressed.

Rifle is going back to Arizona for checking. They can clean the sombitch too!

Selling agent is sending back for me. Says the POF's have been flawless for them and it might be an ammo issue. Wait a minute here. I have thrown everything I've got down the barrel. 147, 149, 168 and 175 match grade. All will fail to eject.

We were banging 9" steel gongs at 600 yards with ALL of that ammo. Hers just kept jamming. Such a thrill killer.

The selling agent said that his, throws the spent shells 4 to 5 feet over his shoulder. This one never did. Always dropped them on the table. I thought it was normal, until the frequency became worse for the jams.

Thanks guys.

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4 hours ago, 98Z5V said:

Gas port diameter on the barrel?

  Or something in the Gas system , Block could have out of spec passages or an alignment issue with the Gas Adjuster or switch ,also could be binding of piston rod or Piston . I have seen Pistons bind when warmed up & bending Piston Rods .Still could be in the Buffer system or something slowing down the BCG . 

The Gas Port size was my first thought also on both of these rifles .

 JT , they replaced the Gas System & BCG & it didn't change anything ?     

   I can see the Rifle having issues when used firing suppressed for extended periods , but 100 rounds is kinda low , but suppressed weapons are really not all that reliable for extended firing periods , in my experience , they need constant maintenance to keep them running with out issues . 

   If the rifle is under warranty , send it back till they fix it .

    There really is no difference in the Piston & DI systems as far as what the purpose is , its to cycle the Action for ejection of the spent case , thats all they do , one is direct linked mechanically with Piston & a connecting rod to force the BCG to extract the spent case from the chamber & the DI does the same thing , only with direct spent Propellant gas pressure to accomplish it. Both rely on the proper amount of Gas pressure from the Barrels Port to do this .

  Both systems have pro's & con's , with DI its the direct Gas of spent propellant into the Action & with Piston systems , its more moving components & weight , though they seem to be not much , they still both need the proper amount of spent propellant gas ( Gas signature ) to function.

  The issue with weak ejection can be several things & if it locks back the Bolt on last round in the Mag.every time ( if it has this feature ), its not short stroking , more likely an Ejector issue or could be the Extractor is holding on to the spent case too long or more likely too much Extractor pressure on the base of the Cartridge .

   I have an old  24" AR 15 , this rifle has so many rounds through it , I can't even guess , this Rifle I built some where around 1978 , rifle length gas system , DI & Rifle Stock , its just started an issue the last time I shot her for velocity testing a new Powder , the spent cases are just dropping out of the Ejection port , some , because I was Bench testing, were dropping onto my hand & the little batsiges were hot , The first thing I will do is change the Buffer Spring , to see if it changes , I will bring Bolt Components with me & change individual Bolt components to see where it goes . My plan is for doing this tomorrow , Friday , I would go today but have to sign for a FedEx package .

 Its difficult to trouble shoot an issue like these with out having a hand on the Rifle .

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Here are 3 pics from this weekend of fun. Lonely walk was taken through a 17 X spotting scope, from the 70's. Once I got that long range stuff figured out, the silhouette pic makes me feel good about 600 yard shots. Thats when banging the gong started. Her POF was the first one we adjusted and she was banging the steel before I got mine adjusted. We had a very knowledgeable guy on the range to help us that day and we kept ammo waste to a minimum.

Damn, good shooters are good people to learn from!


Lonely Walk.jpg

Bent Shell.jpg

Silhouette 7-17.jpg

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   I have had Cartridges like the middle photo , Ejection issues or short stroke & the bottom of the Bolt Carrier stripping the Case from the mag instead of the Bolt Face .  I pull the Bullet , save the Powder charge , re-size the case without de-priming it & reload the round . then shoot the dents out , GTG.:thumbup:

   I had a BCG made by a reputable manufacturer & had to swap out their Ejector Spring for a factory DPMS one & it fixed the ejection issue  . Sometimes its the Extractor itself or too heavy of spring pressure , some install two O-rings with the Extractor Spring & it can cause issues . When you get something like this , you have to play Detective to solve it .

Edited by survivalshop
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Well, I hope the factory can resolve this. All of the ones that were bent, are the same brand. PMC 147. That is why I gave credibility to the ammo issue. BUT, all of the weights we threw got stuck. The other cartridges did manage to make it into the chamber, without getting turned sideways and getting destroyed. Still, the bolt lodged against the spent case in the port and didn't lock on to the new cartridge yet. Those cartridges slid in and out of the chamber and rolling them on the bench, didn't show any distortion, so we reloaded the magazine and fired those rounds. 

It was so annoying to have this happening so often. In 6 hours of shooting, 6 got bent like this and another 10 got stuck. This never happened on the last round, by the way. We were loading 3 or 4 rounds in our mags at a time. Group shots.


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