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Discussion Starter #1
Hello all. I have a ps90 that i am having some trouble with. When i rack the bolt all the way back it doesnt want to close. It seems to get stuck back. When i take the trigger pack out and rack the bolt it works perfectly and slides free. So i assume it is rubbing on the hammer? What can i do to fix this? Any help would be greatly appreciated!
 

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Discussion Starter #2
I just cleaned it entirely also to hope to fix the problem. To no avail
 

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Discussion Starter #3
Do i need to lube it up more? Ive only put a touch of oil on the rails. Maybe my recoil springs are wore out?
 

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So if you take the hammer pack out, the firearm cycling operates correctly with no issues. But with the hammer pack installed you have problems.

Let's see a pic of the hammer pack.
 

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Is your Hammer pack in factory configuration?
How many rounds do you estimate have been fired downrange ?
 

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Discussion Starter #6
Yes it moves completely freely when i take the trigger pack out. I put the aftermarket hammer from (i cant remember his name) on this forum. Makes it a shorter and lighter trigger pull. Thats the only difference from stock.
 

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Discussion Starter #7
I thought it was because the bolt carrier was rubbing on the top of the hammer because it was rubbing the finish off of the hammer. So i smoothed it up with a fine file and some emery cloth. But still sticks back
 

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Discussion Starter #8
I have put around 3-4k rounds through it id say.
 

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Pictures are worth a thousand words. I need to see what the hammer pack looks like.

Do not do any modifications. Filing the hammer to remove the finish changes the dynamics of the components.

Is the hammer new to the pack?
Was it reassembled properly?
Is the sear malfunctioning?

If it cycles fine without the hammer pack but screws up the function when the hammer pack is reinstalled means its most likely a hammer pack issue.

Check the obturator and see if its malfunctioning - the cartridge door that sits under the bolt.
 

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Discussion Starter #11
Yes the hammer is aftermarket from a guy off this site that sells them.
 

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Discussion Starter #12
The bolt moves very free without the hammer pack installed. Once installed it has a drag on it and dont move freely. Still functions and shoots
 

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Try this.

Insert the hammer pack hammer cocked.

Pull back on the charging handle. There should be little to no resistance.
(No more than the bolt group springs)
Release the charging handle, do not ride it.

Fire the weapon by pulling the trigger and letting the hammer fall. MAKE SURE YOUR PS90 IS UNLOADED.
You should hear the hammer fall and hit the firing pin.

Pull back on the charging handle.
You should feel a heavy resistance as the bolt group engages and retracts the hammer while pulling back on the charging handle.
Release the charging handle, do not ride it.

Fire the PS90 and you should hear the hammer fall and hit the firing pin.


I need a little time to examine the hammer pack to make sure it was reassembled properly. Cursory look indicates it was done properly.

You say the PS90 operates properly but you are concerned that the new hammer is causing issues. Remember, you switched from a polymer hammer to an aluminum hammer.....there will be a different feel to the PS90 charging process. You now have metal to metal contact with the aluminum hammer.

I'm not liking the way the hammer looks though.
 

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I really need a picture of the underside of the bolt group. Your hammer looks like it beaten up and what I suspect is that when you charge it by hand, you feel the bolt group drag across the hammer and it is catching on some of the spurs I see on the hammer. When you use it at the range, you do not feel this as the firearm charges itself with no help from you.

I see some nicks on the hammer that may be catching the bottom of the bolt group. Run your finger over the hammer and if you feel any spurs, you can try to file them out but I would be very careful doing this.
 

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Discussion Starter #16
I think everything is fine but i think the springs are weak and not strong enough to push it forward with the pressure of the hammer pushing up against the bolt carrier. Is this possible?
 

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Not likely. Springs do fail....its called metal fatigue but these springs were made to last thousands and thousands of rounds. You can replace them easily. You can get the parts at Midwest Gun Works but if you do buy the springs, don't forget the c clips. They are a one time use item.

The bottom of the bolt group looks ok.

Are you saying that the issue is halpening as the bolt moves forward and not as the bolt moves rearward?
 

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I have to correct myself, there is a drag on the bolt group as it moves over the hammer face and the hammer face rides on the bottom of the bolt group for about 40% of the rearward then forward movement.

But I got a plan.
 

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I think you are feeling the roughness of the hammer face and the drag of the hammer face on the bottom of the bolt group. This is how the PS90 cycles from a fired setting.

1. The bolt group moves rearward and the rounded rear edge of the bolt group cocks the hammer which allows the auto sear to engage into the hammer notch. This happens in the first 60% of rearward movement of the bolt group.

1A. You start to feel a heavier resistance.

2. As the bolt group continues to move rearward, the bolt group bottom slides against the hammer face for about the last 40% of rearward movement. This can be felt as you manually cycle the firearm. For about 60% of the initial rearward movement, there is hardly any felt resistance. You then feel a hump as the bolt group drags across the hammer face and the last 40% of movement you can feel the drag.

3. As the bolt group moves forward, the initial 40% of forward movement you can feel the drag of the hammer face on the bottom of the bolt group. The remaining 60% of forward movement, there is no resistance as the bolt group has moved forward enough that it no longer is sliding against the hammer face.

4 When the bolt group moves forward, it strips a round from the magazine and the continuing forward bolt movement chambers the round. At the very last bit of forward movement, you will hear a click. This click is the auto sear being tripped.

5 The cycle repeats once the trigger is pulled, the cartridge fires, and the bolt group moves rearward ejecting the spent cartridge. Back to 1.

To hear and see this movement, you can do this.

Remove the barrel group.
Remove the bolt group.
Remove the butt plate by sliding it up.
Replace the bolt group.
Replace the barrel group.

You now have an assembled firearm without the butt pad installed.

Get a small flashlight or other light source that allows you to see the top of the hammer pack and the back of the bolt group, looking into the rear of the firearm from the removed butt pad. I use a small flashlight held in my mouth so I have both hands free.

Looking into the rear of the firearm where you can see the hammer pack and the rear of the bolt group lit by the flashlight or light, you can now manually cycle the firearm and see and feel how the bolt group cocks the hammer and then you will also see and feel how the hammer face rides the bottom of the bolt group for the last 40% of cycle motion.

This is normal.

What I think you are feeling is the face of the metal hammer riding the bottom of the bolt group during that 40% of rearward movement.

I think your firearm is OK. What I would do though is contact Man Kave and buy a new polymer hammer and replace the aluminum hammer. Or if its the short pull hammer, buy a new one. If he is OOS on the blue hammer, I have one sitting in my safe.

I would not have filed the hammer face but the bolt group is a much harder metal so the aluminum hammer will not damage it as the bolt group slides over the hammer face. Eventually, the hammer face may even smooth out again.

Let me know if this is what you are feeling cycling the firearm. But as I indicated, it is probably nothing to fret over.
 

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Discussion Starter #20
Yep exactly as i thought. It sure is kinda aggravating to have it get stuck when trying to go back forward. I will try a new hammer for sure. Maybe the polymer hammer is slicker? Thank you very much for all your help!!
 
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