Safety Sear

[ffemt596]

How important is the safety/forward sear in the PS90? I know it is to prevent out of battery discharge, but is it necessary in semi-auto only? It is no longer on the FS2000 because it is said not to be needed on civi models. Why is it still on the PS90? Is it needed for safety?

[M1P90]

FNH-USA answered this question on the question and answer area. They said the forward sear is not necessary and they will change it out when their supply runs out. They changed the White Ring Sight to the Black Sight but only after they used up the supply of the old Sight.

http://fnforum.net/viewtopic.php?t=4416

The # 5 question doesn't really ask/answer your question but it is close. I remember reading somewhere that the front safty sear will eventually be changed out because it is not necessary for the civilian version.

[HK SD9 Tactical]

How important is the safety/forward sear in the PS90? I know it is to prevent out of battery discharge, but is it necessary in semi-auto only? It is no longer on the FS2000 because it is said not to be needed on civi models. Why is it still on the PS90? Is it needed for safety?

Not required in semi-auto weapons.

The forward safety sear (really a misomer - more of a hammer release sear in auto mode) is what releases the hammer in automatic mode as the bolt slides forward and the trigger has been continously depressed durring cycling.

As the trigger is pulled, the firearm discharges and the bolt group moves rearward recocking the hammer and engaging the forward and rear sears. As the bolt slides forward, it strips another round from the magazine and chambers the round into the firearm. Once the round is chambered and the firearm achieves 'in battery status', the bolt while still moving forward catches the forward sear and releases the hammer (providing the trigger is still depressed - thus keeping the primary sear dis-engaged) allowing the hammer to fall and strike the firing pin resulting in the firearm discharging and the cycling action to continue again, and again, and again until the trigger is released causing the primary sear to engage again. In this scenario, the rear sear is held 'back' by the triggers continous pull and will not engage, allowing the forward sear to retard the hammer falling until the firearm achieves 'in battery status' as indicated above.

In semi-auto firearms, there is no need for the forward sear because as the bolt group moves rearwards re-cocking the hammer, the primary sear catches the hammer and holds the hammer until the trigger is released and then pulled again to release the hammer a second time once the firearm achieves 'in battery status'.

If I explained the mechanism correctly you should be able to understand that there is no need for the forward sear in semi-auto mode as the primary sear prevents the hammer from falling until the firearm is 'in battery' AND the hammer is released by pulling on the trigger a second time cycling the firearm, then third and fourth and etc....

In the semi-auto firearms with two sears, the forward sear provides a duplicate function of retarding the hammer until the firearm is 'in battery', something the primary sear is designed to do.

Hope I did not muddy the explanation of what the sears functions are.

[2Blown98]

Awsome explanation. One thing though, in your third paragraph, your description for semi-auto don't you mean secondary sear? At least that's what I'm calling it (my terminology may be wrong). I would think what the trigger actuates would be your primary, the secondary would be what catches the hammer when the trigger stays depressed, and then your third or foward sear which is only usefull in autos (I think). Does that sound right? Just trying to make sure I understand

[ffemt596]

Anyone with a dissenting opinion?

[HK SD9 Tactical]

Awsome explanation. One thing though, in your third paragraph, your description for semi-auto don't you mean secondary sear? At least that's what I'm calling it (my terminology may be wrong). I would think what the trigger actuates would be your primary, the secondary would be what catches the hammer when the trigger stays depressed, and then your third or foward sear which is only usefull in autos (I think). Does that sound right? Just trying to make sure I understand

There are actually two main sear components in the older dark hammer group and with the loss of the 'forward sear' only one sear component in the lighter hammer groups.



As shown in the image, I have the older hammer group which has the forward sear that is not needed.

As the bolt group moves forward and the firearm comes into battery, the secondary sear is disengaged, leaving the primary sear and the hammer release the only two mechanisms holding the hammer back. As the trigger is pulled, the hammer release starts to move back dis-engaging the primary sear. As the hammer release moves further back, the hammer is released and the firearm discharges. As the bolt group moves back to recharge the firearm, the hammer release is still in the rearward position (we ain't fast enough to release the trigger while all this is happening) but the primary sear will catch the hammer as it is moved into the cocked position. As the trigger is released, the hammer release moves forward re-engaging the hammer. Once you pull the trigger again, the sequence is repeated.

So in essence, there are two mechanisms that prevent the hammer from falling again once the trigger is released, the primary sear and the hammer release. If the trigger is still pulled, then only the primary sear prevents the hammer from falling a second time until the trigger is released at which time both the primary sear and hammer release (after re-engaging) provide this function. The forward sear plays no part in this as it will always be engaged until the firearm is in battery as only the bolt group moving forward will disengage the secondary or forward sear. The primary sear provides the function of preventing the firearm from discharging a second time until the trigger is released and then pulled again.

This is why the secondary sear is not needed in semi-auto weapons. It is also why some people refer to it as the 'secondary safety sear', because it will prevent the firearm from discharging until the bolt group is in battery, a duplication of what the primary sear already does.

My terminology is probably wrong as it is very difficult to identify with certainty what FNH calls these components in the hammer group but the gist of the functions remains the same.

Hope this clarifies my meaning.

[2Blown98]

Thanks, that made things much clearer for me. One more question though. How does the drop safety work? I've been trying to figure it out and I just can't get my head around it.

[M1P90]

Here is another picture of the Trigger Pack.

A. Forward safety sear. not necessary.

B. Hammer

C. Rear sear

D. Disconnector.

[HK SD9 Tactical]

Here is another picture of the Trigger Pack.

A. Forward safety sear. not necessary.

B. Hammer

C. Rear sear

D. Disconnector.

Thanks for the clarification on the disconnector. I had not heard that term before and it sounds much better than 'hammer release'.

[ffemt596]

I thought C was the disconnector.