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Discussion Starter #1
Everyone seems to love their PS90, except for the factory optical sight. After trying several rail systems on my P90 in order to replace the crappy optic with my Trijicon Reflex, I discovered that all the aftermarket rails caused my Reflex sight to sit way too high obove the gun. With the sight 3" above the barrel, it was difficult to obtaion a good sight picture while maintaining a good cheek weld on the rifle. Additionaly, the paralax between 50 and 100 meters made the holdover excessive at best. I even tried out the new TR version with the factory flat top. To my surprise, I found the optical rail on the TR to be almost the same height as on the regular version. After some milling, cutting and welding, I came up with the new "ultra low" flat top you see in the pic. Now my Reflex sits exactly at eye level, while still allowing a normal cheek weld.

 

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Good job. I've said it before - if ya got the skills, ya can do all sorts of kewl stuff :)

If I started cutting on my $1500 PS90, I'd have a ball of junk parts pretty quick :roll: :wink:
 

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very nice, this is how the TR model should have been done in the first place.

Suggestion, place a small short low profile rail on the left and right side of the receiver for flashlights, lasers etc...

 

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I find that an optic sitting that close to the bore on the PS90 is going to be less comfortable to use (for me). A chin-weld gives a very comfortable position to look through the optic. Unless you can get the rail down enough so the center of the optic is within 1"-2" of the bore, there's not a lot of point in doing so because it's still going to sit too high for CQB use (that's where lasers come in).
 

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I think the only decent way to get the optic really low is to use some sort of mounting rail over the barrel - not necessarily that quad rail getup from Magazine Parts. But with all the machining people here are doing to their receivers - it seems like someone could do some drilling and work out a lower rail over the barrel - without actually touching the barrel at all.

Then, look down the existing rail, and maybe just barely be able to see thru an eotech that sits over the barrel - very low...

Just an idea...

With me shooting at 50 yards, I'm fine with my current setup. And, I have a decent guestimation at where to position my eotech reticle even for close quarters shooting, based on where my laser sits in the window when I activate it.
 

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I think what you have done looks great, however, from a functional perspective (pun intended) it may have diverged from the original intent of the rifle's design. From what I understand the P90/PS90 was designed so that when you mount an optic you don't have to hold the rifle up so high to see through it. It was designed to allow you to keep your head up straight and have the optics come to you without having to raise the rifle so much.

http://ps90forum.com/Video/P90.wmv
 

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Fargo said:
very nice, this is how the TR model should have been done in the first place.

Suggestion, place a small short low profile rail on the left and right side of the receiver for flashlights, lasers etc...

The easiest way to do that is to buy the TDI/Command Arms TPR-16 rails for the P90/PS90. They'll work perfect.
 

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KAHR said:
I think what you have done looks great, however, from a functional perspective (pun intended) it may have diverged from the original intent of the rifle's design. From what I understand the P90/PS90 was designed so that when you mount an optic you don't have to hold the rifle up so high to see through it. It was designed to allow you to keep your head up straight and have the optics come to you without having to raise the rifle so much.

http://ps90forum.com/Video/P90.wmv
I beg to differ. Why then are both factory sights (white and black ring) low to the bore?

The FN PS90/P90 system is designed to be compact and easy to conceal.
 

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Fargo said:
The FN PS90/P90 system is designed to be compact and easy to conceal.
i agree they were made to be compact but i really don't think concealment is on the minds of most military forces.
 

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wildcard said:
i agree they were made to be compact but i really don't think concealment is on the minds of most military forces.
Every effort has been made by FNH engineers to make the P90 & PS90 as compact as possible. No doubt if this was no concern, FNH engineers wouldn’t have designed the 50-round box magazine to run horizontally along the top of the receiver and locate the factory optics low to the bore.

The only purpose I can see for having a "chin weld" height optic on your PS90 is if you plan to do allot of shooting while your wearing a gas or riot mask. If that is your intended purpose for your PS90, then I digress.
 

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The cover of the 2006 FNH Catalog shows an operator using the P90 USG with a gas mask. Chemical warfare equipment is definitely a consideration when designing a weapon system for the military. Without a gas mask, I sometimes find that the reflex sight is too low to the receiver so the magazine edge sticks into my cheek. With an aftermarket rail and EOTech, the chin weld feels very comfortable and I have a "wider" FOV. I'll have to agree that a laser close to the bore is probably you're best solution for sub-25yd shots. I find that when zero'd at 50 yd, I'm shooting only about 1" low at 25 yd (which isn't a whole lot if you're aiming COM).

FWIW, the P90 was designed originally to be a spray and pray weapon for REMF's (engineers/techs, aircrew, loaders, ground crews, etc...) as an alternative to a sidearm or typical submachine gun.
 

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Discussion Starter #13
Gas Mask?

I wore a gas mask for 4 years in the miliotary and frankly never want to wear one again. Besides, I think I would get some strange looks on the range if I was to start firing my gun while wearing one. Correct me if I'm wrong but the PS90 is a civilian rifle, why would it need to accomidative for LE or military use? I made this weapon to suit my personal shooting style and it works well for me. I am used to a conventional shooting stance with weapon shouldered against my cheek on the side of the rifle. In this position the optic is perfectly aligned with my eye, allowing quick aquisition of the target.
 

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Re: Gas Mask?

UziDuzit said:
Correct me if I'm wrong but the PS90 is a civilian rifle, why would it need to accomidative for LE or military use?
You're correct, but I never said the PS90 was designed for the military. However, the PS90 is based on the P90, which WAS intended for military units.

I am used to a conventional shooting stance with weapon shouldered against my cheek on the side of the rifle. In this position the optic is perfectly aligned with my eye, allowing quick aquisition of the target.
Like I said, even the stock reflex sight height is too low for me to get a comfortable shooting position with the magazine right in the way. The chin-weld with an EOTech gives me the best FOV and faster acquisition of the target. Since all the optics/sights are going to be way over the bore center line, might as well find something that is comfortable to use. It looks like for iron sights/optics to be as close to the bore as possible, they'd have to sit right on top of the magazine.
 

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Uzi,

Would you be interested in modifying my triple rail?

Cost?

I'm trying to decide between selling my triple rail for the new USS sight versus keeping it, this mod looks like a good alternative.
 

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Discussion Starter #19
your kidding right? the serial number is 1/4 inch above the square indent on the front of the receiver.

The complete job with refinishing would run $375
 
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