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Discussion Starter #1
Kind of hard to describe, but here goes....I shot the gun this evening for the first time. I shot slow, 5 shot strings (SS197). After each 5 shots, I removed the mag, cleared the remaining round (down into the catch bag), and went to check my target for grouping/sight alignment. Each and every time, when manually charging the weapon, the first round instead of firing with a sharp staccato crack, was sounding like a low pressure squib, with the internals seeming to operate in slow motion. It seemed as if I could hear/feel the bolt moving in a slow, two part , backward-forward movement. Rounds 2 through 5 of each string had a very crisp, sharp, report, and the bolt's movement was what I expected...just as crisp as any of my other rifles.

This happened 10 times in 50 rounds...every time I manually charged the rifle. My initial thoughts before I connected it to being the first round of each string, was that the quality control of the bullets was suspect, and that I was experiencing lightly loaded rounds. This appears not to be the case...as follows.

I handed the rifle over to an other member at the range who had been watching me shoot (he thought the rifle was cool), and let him fire off some ammo. He fired a few, and then I asked him to manually cycle the action. We did this a few times. Without me telling him what I was experiencing, I asked him what he thought. He volunteered that some of the rounds were quite lightly loaded. After asking if it was the first round of each string that felt light, he concurred.

Each time I chambered a round, I did so by pulling the charging handle back as far as it would go, and then let go, I did not ride the handle into battery.

I'm wondering if while cycling the bolt manually, the moving parts group might not have been going completely home, but far enough to release the (don't know the proper terminology) sear that's at the very front of the hammer group(the one that clicks loudly).

Anyone else experience this???? Any thoughts???

For informational purposes, with the SS197, the rifle was initially shooting a few inches high and to the right at 50 yards. Once sighted in, I was able to get all of my groups within 4 inches. Each group had 4 rounds in a 1 to 2 inch horizontal line, with one flyer in each 5 shot group opening it up to 4 inches. Don't know for sure, but I'm guessing the flyer was the first shot of each group.
 

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Interesting.
The fact that you pulled the charging handle back and let it go makes this case very curious since the first round is being slammed home with approximately the same force than you would expect from the blow-back stroke.
I don't think it has anything to do with the safety sear. Honestly, I'm stumped.
I've shot three separate brand new PS90s and never experienced what you're talking about. Also, I've never heard anyone else mention this peculiar problem.
If I had to guess I would say that the bolt is slaming home with more force when manually charged, and that some gunk in the chamber is acting to delay the blow-back stroke on these harder-slammed rounds.
 

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Discussion Starter #4
That describes it better than I did....It feels like a delayed and slowed down blow back stroke.

Promoted Pawn said:
ps. were the flyers high, low, or random?
All were about 2 to 3 inches high. Some were centered above the horizontal string, and some were above but towards the left side of the string. The other fours rounds of each string were in an almost perfectly horizontal line, 1 to two inches across.

All shots were made with both hands resting on sandbags, with the rifle pulled into the shoulder. I was still moving around a bit myself (not too steady anymore), but I don't think the flyers were me.

Now that I've got it sighted in, next time I go to the range, I'm going to manually load each round (dumping the automatically loaded 2nd round), and see where they print. At least that will tell me if the flyers are the first round of each string.
 

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Very, Very interesting. It sounds like something is obstucting the action.
I would suggest a complete strip and clean and LUBE (and 1 drop in the chamber) Make sure the anti bounce weights are free moving and use a dental pick to clean the chamber(where the brass ends). Make sure the barrel is free moving and can move back 1 cm.(nothing interfering with the movement). Do some dry fireing so you can hear and feel how the trigger and action feels.
Go to the range and see if that does the trick.

Good Luck!!!
 

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Same thing happens to me...

I have had the same experience, only with my reloaded ammo. Factory ammo does not produce the same effect you are describing (at least not in my rifle).
It is wierd, only the first round. Not every time either, I'd say about 50% of the time it happens with my reloaded ammo. My reloads are not max. loads and are purposely loaded somewhat light.
I check the case lengths and trim if necessary.

I have no explanation for it.
Anyone else have any clue to what's going on?
 

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Discussion Starter #7
I spoke with my BIL who's a real collector and enthusiast. His answer as to what is going on was given in a matter of fact way. Wanted to run this by the members...

He said that the when manually racking a round into the chamber, I might not be getting as tight a gas seal, as when the weapon's action performs the same function. He hasn't handled a PS90 yet, and he wasn't basing his info on this being the actual case with the P90 system, but he was surmising that when autoloading, the bolt might be moving further to the rear than when racking by hand, and in the process, it's under higher spring compression as it gets thrust forward chambering a round, creating a tighter gas seal.

He told me that the low recoil impulse and the slowed blow back I was feeling was due to the poor gas seal with some gas leaking around the cartridge case.

He has well over a thousand guns in his collection, and informs me that he has a few that do the exact same thing on the first round.

Sounds like it makes sense. Any thoughts?
 

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Discussion Starter #9
Those who have not experienced this...how do you rack the first round into battery? Do you easily/slowly pull the bolt fully to the rear and then let go, or are you forcefully throwing it back before letting it go, kind of creating a little inertia as it bounces off the back of it's travel?

I've been doing the former and not the latter, although at my next trip to the range, I'm going to be a little more forceful when chambering a round, just to see if there's any difference.
 

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:-x
I always practice the "under fire" way. Pretend you are under fire and see how you charge the round. Very forceful and fast.
 

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I ahve shot my PS90 over 5,000 rds and never experienced or noticed anything like you did.
Try another box of ammo and let it rip instead of single loading and see what happens.
 

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If all esle fails... read the manual.

The manual that came with mine states in the "loading and cocking the carbine" section: "Pull the cocking handle completely rearwards and then release it."

I would think that by releasing the cocking handle from the full, rearward position provides enough force to fully seat the round in the chamber. Unlike most other high velocity cartridges that have tapered casings, this round is untapered and will not seat as easily a its tapered cousins. That is why the factory uses a special coating on it to allow for easier extraction of the spent casing from the chamber.

Cocking it as you would a pump shotgun, would likely result in a loss or reduction of pressure that would affect the first round only. Next time, pull that sucker back and let it go, slamming the round home, and see if that doesn't cure the problem.


:-x
 

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Discussion Starter #14
Re: If all esle fails... read the manual.

Next time, pull that sucker back and let it go, slamming the round home, and see if that doesn't cure the problem.


:-x
That's exactly what I have been doing.
 

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I am bringing this one from the dead but since I am seeing the same issue, was it ever discovered what was going on?
 

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I will ask what could have been asked of the OP. Is your PS90 new ? I did not have this issue when mine was new but I hope yours just heals.
 

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This is back from the dead ... I just could not resist the chance to "opine" early in the day.
A few things have changed since 07, one is the introduction of A/E ammo which is infamous for FTF's and mis feeds which often leads to a powder dump into the internals. If that happened ??? only a very thorough cleaning & re lube will suffice IMO. Which is a safe statement as far as I'm concerned, being a glutton for punishment and using A/E for product testing I'm unfortunately all too familiar with the dreaded powder dump.
Another change is that the weapon has been produced in greater numbers since it's distribution level back in 07 putting the platform in more enthusiasts hands.
I would disregard the first members reply about the operators charging function being approximate to the mechanical blow back function. The later is significantly different due to the force being exerted from the round. I do like what the OP's collector buddy thought.

I would clean & lube everything and reference the manual paying attention to the moving parts group. To me as long as it does not fail to fire, I would not be worried, per say, if the weapon is used - vs - new determines what factors can come into play for example.
If new ... did it get the proverbial owner cleaning ? ( many weapons come with heavy preservative coatings )
If used ... in addition to contaminates from use ,there could be a bent or worn rod in the MPG or a sacked spring ???
Just saying , I have never seen the rod or sacked spring issue in a MPG but just throwing out examples.

It could be ...( don't get offended ) an over anxious user ... meaning maybe your unusually aware of mechanical function/ it could just be you.
To me if it is not failing , it would not concern me too much. The 2 different actions man vs mech function of weapon are vastly different.

One could always make a vid and post it up , (a picture or video says a 1000 words) there are many here whom would help ...I would think.
Just my .02
 
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