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Discussion Starter #1
I've got a good friend in another state who also owns a couple of PS90's. He recently took them out for some cold weather drills (24F) and both would start jamming after 50rds of rapid fire, essentially becoming manually operated single shots. He's a stickler for proper cleaning & lubing so I doubt those are the culprits. Anyone got any suggestions as to the cause and possible cure? Thx!...
Tomac
 

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Well, below freezing, it depends on the oil.

A guy on the Sig Forum did a test of various oils at below freezing temps. Breakfree CLP seemed to run even at below freezing. Maybe use that...

FN_PS90 - didn't U have some misfires or something on your last trip when U used that graphite?

I'd try the Breakfree first. Depending on what oil he used and the temp, it may have interfered w/ other guns as well. Who knows...
 

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Discussion Starter #4
ShipWreck said:
Well, below freezing, it depends on the oil.
A guy on the Sig Forum did a test of various oils at below freezing temps. Breakfree CLP seemed to run even at below freezing. Maybe use that...
FN_PS90 - didn't U have some misfires or something on your last trip when U used that graphite?
I'd try the Breakfree first. Depending on what oil he used and the temp, it may have interfered w/ other guns as well. Who knows...
He uses Miltec so I doubt that's the problem, especially considering how little is used to lube the PS90. Plus, the primary malfunction seems to be the trigger isn't moving forward and resetting like it should, doesn't sound like anything to do w/the breechblock and the trigger pack is dry and not supposed to be lubed anyway. What's puzzling to me is the 50rds of failure-free rapid fire followed by the malfunctions in both PS90's. Hmmm...
Tomac
 

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Tomac said:
ShipWreck said:
Well, below freezing, it depends on the oil.
A guy on the Sig Forum did a test of various oils at below freezing temps. Breakfree CLP seemed to run even at below freezing. Maybe use that...
FN_PS90 - didn't U have some misfires or something on your last trip when U used that graphite?
I'd try the Breakfree first. Depending on what oil he used and the temp, it may have interfered w/ other guns as well. Who knows...
He uses Miltec so I doubt that's the problem, especially considering how little is used to lube the PS90. Plus, the primary malfunction seems to be the trigger isn't moving forward and resetting like it should, doesn't sound like anything to do w/the breechblock and the trigger pack is dry and not supposed to be lubed anyway. What's puzzling to me is the 50rds of failure-free rapid fire followed by the malfunctions in both PS90's. Hmmm...
Tomac
I'd say Militec may not be the problem, but Militec sucks compared to Break Free CLP. First off, CLP is the approved lube/cleaner according to FN Herstal and the US military. CLP is rated well below 0F (-50F or lower).

24F is not cold at all and feels like summer compared to ambient temps in the North. We're not that far north and it's 1F right now with a -20F windchill. It's supposed to be below 0F the rest of the week with windchill below -10F.

Try the trigger pack graphite lube (you could alternatively use a graphite pencil...) but it most likely just needs to be broken in.

Clean the chamber and use Break Free CLP. Militec-1 is not a cleaner and is a rather poor lubricant. FN Herstal recommends the use of CLP that meets MIL-PRF-63460 (Break Free CLP is such an approved CLP).
 

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If it were the mags, then his hammer would be reset. When the mags jam up, the next cartridge isn't loaded in the ramp of the mag, but the case should have been ejected and the hammer reset.

I think his friend needs to give the chamber a thorough cleaning with an approved CLP and check for rough spots. This is a blow-back weapon so there's not much that can go wrong like a direct impingement gas system.
 

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It sure sounds like a trigger bar lube issue. It is either not lubed enough or needs more lube. Really though, 24 degrees is not cold at all as far as lube goes. I bet that the cold weather malfunction is a coincidence and it would be doing the same thing even if it was warm. The only cold weather issue I've had with mine was the stock optic fogging up. That was really frustrating.
 

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Discussion Starter #9
septo said:
It sure sounds like a trigger bar lube issue. It is either not lubed enough or needs more lube. Really though, 24 degrees is not cold at all as far as lube goes. I bet that the cold weather malfunction is a coincidence and it would be doing the same thing even if it was warm. The only cold weather issue I've had with mine was the stock optic fogging up. That was really frustrating.
It could be the trigger bar, trigger pack or both acting up in the cold. I left one of my PS90's out all night (sub-freezing) and couldn't duplicate the problem, but then mine have graphite on both the trigger bar & trigger pack. I'll have to suggest the graphite to him and see if that helps.
Tomac
 

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Discussion Starter #11
metroplex said:
How many rounds has he gone through in the past without any problems?
I don't know specifically but at least 500rds.
Tomac
 

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Discussion Starter #13
ShipWreck said:
I'm wondering if he can use CLP and then try to recreate the situation to see if it happens again.
I've asked him to try graphite in the trigger pack and then test again in cold weather.
Tomac
 

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Discussion Starter #14
Update: This problem seems more reproducible if you hold the trigger back hard after dry firing then manually cycle the action before releasing the trigger. He say neither of his PS90's will reset the trigger. I tried it on mine and one has no problems resetting and the other is sluggish but resets about 90% of the time. Anyone else care to try this and report back? Thx...
Tomac
 

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Tomac said:
Update: This problem seems more reproducible if you hold the trigger back hard after dry firing then manually cycle the action before releasing the trigger. He say neither of his PS90's will reset the trigger. I tried it on mine and one has no problems resetting and the other is sluggish but resets about 90% of the time. Anyone else care to try this and report back? Thx...
Tomac
If you dry fire, HOLD the trigger down, and cycle the action, the hammer should reset. When you release the trigger, the hammer should NOT fall and should be caught thus being completely reset.
 

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This is a problem I experienced when developing a reduced trigger pull spring. What Tomac is talking about is not dry firing the weapon (letting the hammer fall), but simulating a fired condition with the bolt back and the trigger pulled. Release the bolt, then release the trigger, the disconnect resets the hammer caught by the sear when released. Using lubricants in the hammer group can create a sluggish trigger return in lower temperatures. This is another reason not to reduce the trigger pull too much if reliable operation is desired in low temperature conditions. Best thing for this is to keep the hammer pack relatively unlubricated and clean from excessive, temperature sensitive oils.
 

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My PS90 trigger works properly (as in resets, functions, etc...) just like the trigger on any other properly maintained and functional firearm.

I recommend your friend get in touch with FNH asap.
 
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