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A post today reminded me that I have been meaning to make a "mini-faq" on the PS90. So, here we go...

Note - This FAQ will continuously be updated and added on to as time progresses and new information becomes available...

UPDATED 12-07-08


Q: What is a PS90?

A: The short answer to this is that it is a civilian version of the P90.

The FN P90 came into service in 1994, and it was a 50 round, fully automatic personal defense weapon. It was designed for the 21st century - to provide a lot of firepower in close combat situations, and to be extremely small and light. Also, the 5.7x28mm round that the gun is built around was developed to injure troops wearing body armor. The P90 can shoot it's 50 round mag in full auto mode in less than 4 seconds.

The PS90 is the civilian version of the P90. The PS90 has a 16.04" barrel to make the gun civilian legal in the United States, and the PS90 is semi-automatic (instead of being fully automatic). In addition, civilians do not have access to the armor piercing military/law enforcement SS190 round. But that's okay. We still have lots of cool stuff for the gun!

The gun is also unique in that it is FULLY ambidextrous, and the expended shell casings drop straight down. Furthermore, the gun has a 50 round magazine, and the magazine sits on top of the weapon's stock. This positioning of the magazine allows the gun to be fired easily while in a prone position.

More info on the PS90 can be found at FN's website here: http://www.fnhusa.com/products/firearms/family.asp?fid=FNF009&gid=FNG006

Q: Where can I get a PS90, and what is the average price?

A: Many stores, including many online dealers, sell PS90s. Decent prices can range from $1200 - $1699. Prices came down after they first hit the market in 2006 - but with the Democrats coming into power for 2009, prices seem to have gone back up again. It is doubtful $1200 new PS90 deals can be found any longer.

Originally, black colored PS90s went for a premium of $100 over the green models. Now, it seems that the OD green PS90s are a bit harder to find, and the black models are common place.

I won't list specific vendors in this FAQ, as to not cause future problems with sponsors. But, anyone on the site can help you with cheap, online dealers to buy from. And, I have seen both new triple rail PS90s and new USG model PS90s as low as $1199 at Houston gun shows (in 2007).

(I paid $1499 for my black PS90 in Dec 2006)

Q: What's the deal with the different colored ring sights (optics), and how do they compare to the tri-rail PS90?

A: When the PS90 first came out - we were all stuck with the white ringed sight. While some guys like it, it really is hard to use unless you are in a brightly lit, outdoor area. Quite often, there is not enough light available for the light collectors to make the aiming reticle visible. Be aware that there is a fix available - the REM3 (an attachable LED). And, this is available from one of the sponsors here on this site.

There is also the black ringed sight. This is called the USG version of the PS90, or even the USSS version. If you want to stick with the stock sight, this may be the way to go. It is much easier to see and use, but be aware that the optic opening is still smaller than many aftermarket optics. So, there are pluses and minuses to going this way (the pluses is that many people want to keep the gun stock - and that the optic is a tiny bit lower to the bore).

The Triple rail PS90 was released after the original PS90s hit the street. It is for people who want to put their own optic onto the PS90. There is no sight on the gun, and there are no iron sights on it either (the standard versions of the PS90 have emergency, iron sights). The optic rail sits a bit lower, but be aware that the two side rails are very short. In addition, if you wish to mount an EOtech, you will have problems using the side rails on the tri-rail PS90. You will have to buy aftermarket side rails to replace the ones that come with the gun.

Q: How can I mount an optic on the standard PS90 (white ringed version or black ringed version)?

A: There are many aftermarket optic rails for the PS90. The price range for these rails also varies all the way across the $ spectrum. Some are standard sized, some are longer, some are lower, and some have back up sights in the rail itself, or can be adjustable.

Taking off the standard ringed sight and putting on an optic rail can be done in less than 5 minutes. All one needs is an allen wrench to unscrew the two stock screws holding the ringed sight in place. Then, you mount the rail in the same place. Typically, purchased optic rails come with the allen wrench you will need, as well as its own set of mounting screws.

Note: You may want to use some non-permanent thread locker on the screws when mounting the optic rail - This will preven any long term vibrations from loosening the screws.

Q: How many rounds can fit into the PS90 magazine?

A: If you live in a state that restricts magazine sizes - then you are unfortunately stuck with 10 rounds mags that cannot be easily modified. The rest of us gets a 30 round mag with the PS90 when you buy it new. Then, you can buy aftermarket 50 round mags for $48-$55 (depending on where you buy them).

Be aware that the 30-rounder that comes with the gun can easily be modified back into a 50 round mag. MPF Tech and Magazine Parts are just two sponsors that sell the cheap modded piece you need. Or, if you want to get the tools out and modify it yourself, we have members here that have done that as well. I personally think spending around $5 for the piece you need is the easiest way to go - Because I know I'd break the mag if I did it myself. :oops:

Q: How do I get side-mounted rails for my PS90, and how do they attach?

A: First, if you buy the tri-rail version of the PS90, you get small side rails included with the gun. Be aware, however, that these included rails are very short, and they will also be unusable if you mount an EOtech on your PS90. You may want to buy longer, extended rails from Magazine Parts. Or, Critical Dimensions and Promoted Pawn also sell extended rails that protrude out far enough to make full use of the side rail even with an EOtech mounted.

Standard PS90 owners also can get side rails on their PS90. There are numerous shapes and sizes of side rails out there (from many different manufacturers). Low profile - extended profile - short - extended length - etc. Several sponsors here sell these side rails. And, prices can vary as well. But, all that is needed is an allen wrench to attach these side rails onto your PS90. The receiver will already have the holes drilled into it. And, typically, the aftermarket rails you purchase will come with their own screws AND a proper sized allen wrench.

What do you do with these side rails once you have them attached, you might ask? Well, they are perfect to attach lasers, flashlights or other accessories. And, even if you do not use them at all, they make the PS90 look better just by having them on your gun. :?

Q: What is the cost of 5.7x28mm ammunition for the PS90?

A: If you do some digging, 50 round boxes of 5.7x28mm ammunition can be found for $16.95-$18 online (Buying in bulk sometimes gets you a better price per box). Be aware that sales come and go, off and on.

Do not be gouged by $25-$30 boxes of ammo at local dealers. Even with shipping costs, purchasing as few as one or two boxes online can come out cheaper than buying local, if they are charging that much per box.

Given the fact that ammo prices are increasing, 5.7x28 ammo looks pretty good right now. Currently, there have been no price increases on the ammo. Remember as well that this is high quality ammunition - not cheap rounds. So, if you find a good price on a 50 round box, it is not very close to the price of 50 rounds of ammo for an AR.

Granted, when buying ammo for the Five Seven handgun, it can be tough to substantiate the cost against 9mm. But, if you have a large bore handgun that you shoot a lot, then justifying the extra cost isn't too hard.

Q: Is there an issue with having an aftermarket optic sit so high up over the bore of the rifle?

This can be a hotbed issue - especially among people who do not even own a PS90 themselves. Logic would dictate that the higher off the bore your optic is, the more variation you will have at distances outside of your zero. But, when one accounts for the fact that the PS90 is made to be a personal defense weapon, NOT a long range sniper rifle, this bore height issue really is a non-starter. You probably will not be shooting this gun out at super long ranges. And, within the stated range of the PS90 (200 meters - which is really stretching it anyway without a magnified optic), the optic height above the bore doesn't really matter much.

In fact, when the PS90 first came out, many people (including members here) even went to modifying and cutting up their receiver, so they could make their aiming optic sit as low as possible.

The stock optic on the PS90 is sighted in at 50 yards. At 25 yards, it will be approximately 2 inches low (you can see a ballstic chart of the 5.7 round, and more info on the PS90 here: http://en.wikipedia.org/wiki/PS90 ). Truthfully after replacing my white ringed sight with an Eotech (which does sit a bit higher), I get the same variation. And, ANY rifle has variation when you shoot at different ranges closer and further than your zeroed distance.

Therefore - get the optic you want, even if it is an Eotech that sits a tiny bit higher than another optic. Once you zero the gun in for the first time, you will be happy with your choice.

Q: What lubricant should I use on my PS90?

A: The PS90 manual recommends Breakfree CLP. However, the manual also recommends avoiding lubes with "teflon" in them - Breakfree CLP does have teflon it it. However, the product is specifically mentioned by name in the PS90 manual. And, a good % of PS90 owners here on this site use it.

Breakfree CLP has been used by this author exclusively on all his firearms for many, many years with nary a problem.

If you ARE worried about this issue, then just stick with the Breakfree CLP - as that has been specifically recommended by name by FNH.

Q: What is the difference between SS195 ammunition and SS197 ammunition?

A: The 195 ammunition has a lead free primer. It also is a "hollow point" round. But, the round does not mushroom and expand in the traditional sense (think handgun hollow points). In reality - the 195 round enters a soft target and then "yaws" (it flips over and faces the entrance channel of the bullet). By doing this, it makes an entrance channel the length of the round at the point that the round "flips".

The 197 Ammunition has a V-Max tip. It is often called a "varmint" round. The 197 round typically does not penetrate at deeply as the SS195 hollow point does, but the 197 V Max round rill fragment and makes an impressive wound cavity.

There is always a debate among 5.7 fans on which round makes the better self defense round. The 195 will penetrate deeper, but the 197 round fragments and can make a larger wound cavity. Your humble admin switched from the 195 round to the 197 V Max round for self defensive purposes. I personally prefer the 197 round.

Be aware too, that the 197 round is cleaner to shoot than the 195 hollow point round is. Your gun will be much cleaner shooting 197. Another point to consider is the lead free primer in the 195 round. By using the lead free primer, the storage time of the round appears to be significantly reduced. No one knows for sure at this point, but based on other similar rounds with lead free primers, the thought is that approximately 2 years is the max time to store this round before you shoot it. The 197 V Max round should store significantly longer.

Note: As per FN, the technical data on the two commercially available rounds is as follows:


Muzzle Velocity from the PS90 is 2,550 ft/s with an energy level of 394 ft/lbs.

Muzzle Velocity from the Five Seven handgun is 2,050 ft/s with an energy level of 255 ft/lbs.


Muzzle Velocity from the PS90 is 2,100 ft/s with an energy level of 391 ft/lbs.

Muzzle Velocity from the Five Seven handgun is 1,700 ft/s with an energy level of 256 ft/lbs.

*** Note, at this time, due to restrictions in access to the military/law enforcement SS190 round, and to the discontinuing of various 5.7x28 ammo types, ONLY the SS195 and SS197 rounds are currently available to the public.

Q: How do I short-barrel my PS90?

A: One can either short-barrel their PS90 - or one can buy a PS90 already short barrelled. CMMG currently sells PS90s that already have the short barrel installed. They are more expensive, but they charge a fair price when you consider the cost of the new barrel, the new flash hider, the labor and the engraving of the receiver.

To short-barrel your own PS90 - one must fill out certain forms and have their application approved by the ATF BEFORE you start the job of changing the barrel. Information on this procedure can be found here: http://fnforum.net/viewtopic.php?t=1219

Be aware that the same paperwork must be completed if you buy a PS90 already short-barrelled from CMMG as well - however, you need to call CMMG first to get the serial number of the model that you will be buying. They will also assist you in what paperwork to complete.

Finally - it should be noted that FN has stated that your warranty on your PS90 will be voided if you short-barrel the carbine.

Q: My PS90 Barrel has some play in it. Is something wrong with my gun?

A: No, your PS90 is normal. The gun was designed to have that small amount of play in the barrel (you will notice this if you try to move the barrel sideways by hand).

In slow motion - the PS90's barrel actually moves inward slightly, and then returns into place. The minor movement of the barrel that you may notice when examining your PS90 is normal. Don't fret. This question comes up a lot, and the gun is supposed to be that way.

Many people can get 1/2" groups at 50 yards, and close to that at 100 yards (with some practice). So, while this gun is NOT designed to be a sub MOA sniper rifle - it is very accurate for what it is designed to be - a personal defense weapon.
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