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Discussion Starter #1
Greetings Everyone,

I thought I would share how my evening went fiddling with my new PS90. Before I even sent off payment for my rifle, I sent off payment for one of Martin's low profile ACOG mounts. I don't own an ACOG but thought for sure I was going to purchase one to mount on this firearm.

After much debate I ended up deciding on a Trijicon Tri Power. With Martin's mount already inbound and knowing an aftermarket rail to mount the Tri Power would put it higher than I wanted, I decided to purchase an ARMS #16 mount which is a mount just for the Tri Power to be used in conjunction with a AR carry handle. I figured the mount Martin makes is to accommodate a compact ACOG meant to be mounted in a carry handle, so the two mounts should interact with one another well.

I bought the ARMS #16 mount at a gun show on Saturday and Martin's mount showed in the mail today so it was time to see if my plan would work. Of course it didn't go as smoothly as I had planned. They didn't interact well as this is not what Martin designed his mount to do. However I was able to break down the ARMS mount into the two pieces that are assembled together and just using the top half of the ARMs mount drilling a couple new holes in the MSW mount yielded the perfect position for my cheek wield



I can't wait till the sight shows. I will be sure to post a finished product photo
 

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Cool. Thanks for sharing. I can't wait to see the final product.

I had to modify msw's mount a bit to use a Special Mount Compact ACOG. One of the machinists at work used threaded hole transfer pins to mark where to drill the new holes. A threaded hole transfer pin is like a set screw with a pointed end. Thread the pin into the mounting hole you want to transfer and press the mount into msw's mount to mark where to drill the hole. I hope that makes sense.

I didn't realize the Arms #16 mount had three pieces. SWFA has a decent pic of the mount here:

http://www.swfa.com/pc-6519-102-arms-16t-trijicon-tri-power-m16.aspx

Where did the stock holes in the msw mount put the Arms' mount?

If it all works out please do a how-to with pictures :D
 

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Discussion Starter #5
Where did the stock holes in the msw mount put the Arms' mount?

If it all works out please do a how-to with pictures
The problem was the ARMS mount has a single large male screw with a female round nut that locks it into place on a carry handle. I originally drilled the hole larger in the MSW mount but then it was not long enough. And that screw is a part of the mount and not replaceable.

Right about that time I noticed two small screws in the underside of the ARMS mount. When I unscrewed them, the mount came apart into two pieces. The holes in the upper mount are threaded and didn't line up at all with the two existing holes in the MSW mount, so I just drilled two holes through the mount, went to Home Depot and bought two 3/4" bolts and it worked out great!!

Pictures to follow as soon as the sight arrives.
 

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Thanks. That Arms mount seems like an odd design if I understand what you had to do. I hoped the Arms mount would just drop right in.

Looking at the SWFA pic it looks like the sight window in the base of the mount is unusable. It looks like it has screws going through it. I wonder why Arms made the mount like they did.

Edited to add:

I'm sure the sight window in the Arms mount is see through. I think it is just an optical illusion on my part thinking that the screws for the upper half of the mount go through the sight window.
 

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Discussion Starter #7
If you were to use the ARMS mount as it was intended, you would have no problem. The MSW mount came with a screw used to secure the mount to the ACOG, but you can't use that screw, as the ARMS mount has a screw permanently attached to the base of the mount. That screw was too short to go the entire way through the MSW mount and still have enough threads poking through to get the circular nut threaded.

In truth, even if the permanently attached screw was long enough to go through, to disassemble the ARMS mount and only utilize the top actually seats the ring lower that if you used the second half of the mount.

As far as the hollowed out sight channel under the ring, the permanently attached screw is secured below that channel. That’s why it’s a male with a nut rather than a female where the screw would screw into the mount and obstruct the use of that sight channel
 

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Can you take some detailed pictures of the Arms mount? I don't suppose there is a way to take out the male screw.
 

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Discussion Starter #9
There is no way to take out the male screw from the lower half of the mount. In regards to photos, when I get home from work I will be happy to photograph the lower unused section of the ARMS mount however the top half of the mount that is now attached to the MSW mount is all locktited togetgher and on my rifle and I don't really want to disassemble it. I will get a top photo though so you can better understand how I did it
 

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Discussion Starter #10
Sorry for slacking!! My sight arrived today and MAN OH MAN, it worked out so perfect!! It's as low as it can possibly get with the receiver the way it is. It's got maybe 1mm clearance between the sights tube and the end of the receiver so its not binding but as close as can be. Photos to come this evening I AM TOTALLY SIKED!!!
 

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That is a great setup. After one look at the factory sights, I purchased an aimpoint mount for TROS. Ended up going with an 4moa Aimpoint M3 (just like on my HK94), the Tripower is an excellent choice, especially for the pending zombie-pocalypse. :wink:

I have no clue as to what FN was thinking when they chose the sights for the P90/PS90. It is a great concept but should have been executed in a similar fashion as Trijicon's optics. Why on earth is it still in production after all these years? :lol:
 

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Discussion Starter #12
Ok, Here is the finished product. I AM IN LOVE!!!

Sexy in her Bikini






Low as it can go






Tomorrow will not come fast enough

 

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Great pics!

I'm glad everything worked out. I know I didn't feel like my rifle was complete until I replaced the white reticle Ring Sight.

Edited to add:

Can you do me one more big favor and take a close up picture of the mount from the front? I'm curious how the upper half of the Arms mount sits in the groove on the MSW mount.
 

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wlcohen, TheBadGuy may not be able to take many more pictures other than with everything in the rifle because he may have everything is Loctited in now. I have some pictures of the MSW mount and how I attached a special ring ACOG mount here:

http://www.ps90forum.com/forum/viewtopic.php?t=391

I'm thinking TheBadGuy did something similar. He said he took the Arms mount apart and didn't use the base with the sight window. I wonder if you can buy the Arms mount without the sight window and save a few bucks? It looks like Arms made the mount that way so it would be modular.
 

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Discussion Starter #17
SS, I will take those requested photos today and get them up

wlcohen, hope you better understand here:

Martin's mount is attached to the gun using the already existing holes in the receiver here



Compliments of Sunset Sam


The ARMS mount is taken apart into two and attached to Martin's mount


SS, Unless you contact ARMS, I do not believe they offer just the top portion of the mount by itself.
 

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Discussion Starter #19
SunsetSam said:
TheBadGuy, great illustrations. Hey, I recognize that middle photo :D
:lol: I made sure to give ya credit as it was a better photo than I could have take, hope you don't mind. While I am at it, the bottom pic is from riflescopes.com :lol:
 

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Discussion Starter #20
SunsetSam said:
Can you do me one more big favor and take a close up picture of the mount from the front? I'm curious how the upper half of the Arms mount sits in the groove on the MSW mount.
Here you go. You can see it sits on the flats and not into the groove like I was hoping the entire mount would do.



Side view
 
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