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Discussion Starter · #1 · (Edited)
Just as the title of this thread says.

I tried to use the muzzle bore sight, but since the PS 90 has a rather long muzzle brake, the stems of the traditional muzzle end lase bore sights do not work.

So, I am looking for one that goes into the firing chamber.
Obviously, a .223 or 5.56 NATO bore sight will not work because this round's shell outer diameter is too big to fit into 5.7x28mm firing chambers.

Thanks all,
Jim

EDIT: I created a makeshift way of laser bore sighting the PS90 in this vid. I posted the vid is Post #13, but for the sake of ease when ppl are doing a search and so they don't have to read other posts that don't directly have solutions, I am adding the vid here.

In the vid, I mention that the PS90 bolt cannot be locked back, but there is a trick to do it: http://fnforum.net/forums/fn-ps90/60398-ps-90-bolt-catch.html



Other Alternatives:
There are other means of laser sighting the PS90; this magnetic unit should work nicely.
Thanks to Kakashi for this vid:


This Sitelite SL500 apparently has a long enough stem that will reach the rifling of the muzzle properly and securely
Thanks to Phansson for this link:
http://sitelite-lasers.com/product_SL500.html


Another trick to sight in your PS90 without the need for any outside equipment is to take down the PS90 and set up just the upper receiver on a steady surface and look through the firing chamber and barrel at a reference point downrange.
Thanks to M1P90 for this trick. See the very next post for his procedure.
 

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For the Ps90 I just take the upper off and set it on a table. Then I turn on my side mounted laser ( 25 foot range) and then look down the barrel and line it up. I then look through my optic and line that up but make it about 8 moa above the dot. That pretty much gets you real close so you can dial it in at the range. :target:
 

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For the Ps90 I just take the upper off and set it on a table. Then I turn on my side mounted laser ( 25 foot range) and then look down the barrel and line it up. I then look through my optic and line that up but make it about 8 moa above the dot. That pretty much gets you real close so you can dial it in at the range. :target:

Good way of doing it to get it in the ball park. :?
 

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Discussion Starter · #5 · (Edited)
I can use my Bushnell Laser Boresighter just fine with an unmodified PS90.
How did you get the stem to reach the muzzle? I had this problem because the muzzle brake is so long that the arbors could not seat to the rifling.
 

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Discussion Starter · #6 ·
For the Ps90 I just take the upper off and set it on a table. Then I turn on my side mounted laser ( 25 foot range) and then look down the barrel and line it up. I then look through my optic and line that up but make it about 8 moa above the dot. That pretty much gets you real close so you can dial it in at the range. :target:
i don't have a side mounted laser, but I tried this trick with just the built in iron sights. I did this trick to get them sighted in before I went to the range. It helps that the factory setting is extremely spot on (at least they were for my PS90, I don't know how out of whack they are on other PS90s out the door).

i used this trick at 25yds instead of only 25ft. So I did not set the aim point as high as 8MOA.
My eyesight sucks so it was an absolute pain just to see the the target lines even at only 25yrds.
This is why I trust a laser through the bore and sighting from that to zero in.
 

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Don't know if this is already answered well enough but I've got the wheeler laser unit it works with all calibers and a strong magnet holds it to the muzzle. GL

found this:
 
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Discussion Starter · #10 ·
Don't know if this is already answered well enough but I've got the wheeler laser unit it works with all calibers and a strong magnet holds it to the muzzle. GL

found this:
This magnet one shows a lot of promise.
Just like what the guy said, one bore sighted to sight all your firearms in. No need for a hodgepodge of different ones.


I have one of these and it works great on my ps90. It is expensive though....


SITELITE : SL - 500
I wish I would've known about this one. That is, if the stem is long enough to reach the rifling and insert far enough in to get a sturdy mounting.

Ive given up on the stem sighters because the PS90 muzzle brake is just too long.
The vast majority of stem sighters have too short of stems and would thus only work on an SBR PS90 with a short enough brake or flash suppressor
 

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Lol, yeah that bore sight fit my tav and ps90, brother n laws sr25 one after the other. it is pricey tho. GL
 
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I wish I would've known about this one. That is, if the stem is long enough to reach the rifling and insert far enough in to get a sturdy mounting.

Ive given up on the stem sighters because the PS90 muzzle brake is just too long.
The vast majority of stem sighters have too short of stems and would thus only work on an SBR PS90 with a short enough brake or flash suppressor
The stem is long enough to easily reach the barrel on the stock PS90. I used it yesterday to sight in my new (to me) PS90.
 

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Discussion Starter · #13 ·
I came up with this cheap-O ghetto method to laser bore sight my PS90.
I bought a cheap chamber mounted .22LR laser bore sight from Sight Mark (their laser bore sights suck BTW) and I did this trick shown in this vid to sight it in to get me on paper at 50yrds.

 

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Discussion Starter · #15 ·
Thanks for the vid!! BTW, there is a way to lock the bolt on the PS90. http://fnforum.net/forums/fn-ps90/60398-ps-90-bolt-catch.html

Thanks for the link to the trick!
I never knew this procedure existed.

I checked my manual and this procedure is not mentioned. I wonder why FNH ceased to print this procedure in current manuals?
My only possible guess is that this trick is a work-around and the ejection port dust cover was never really designed from the beginning to function in this manner. Because of this FNH probably quit including this procedure for the sake of liability and the dust cover door having its leading edges wear out from holding back the bolt assembly while under spring load.
 

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In the "maintenance manual", FN calls out part #273 as the obturator catch which is the plate on the assy that has the projecting tab that catches on the hammer pack when raised upward towards the action area. Nowhere have I found where FN describes using this feature as a bolt catch.:th_confused0024:
 
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