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Discussion Starter · #1 ·
Like most of you with PS90's I found the white reticle Ring Sight unusable. There is the black reticle Ring Sight, but it is $600 and some have said there are quality issues with it. I believe it also has the same shape reticle as the white reticle sight and I didn't like the shape of the reticle for precision shooting. There are a few companies making Picatinny rails, but I didn't want to have a sight any higher than the stock sight if I could help it.

About the time I bought my PS90 msw (Martin) on fivesevenforum.com showed a custom mount he had made for his PS90 to use with a Compact ACOG with the M16 carry handle mount. Later, Martin said he was going to have a production run made of his mount. I never really considered the Compact ACOG, but after seeing how low the sight could be mounted I was interested. I also thought getting a little magnification couldn't hurt and I like that the ACOG requires no batteries.

I decided to go with the 2x20 red crosshair Compact ACOG. I've had the scope mounted for about 6 weeks now and I love it.

The MSW100 mount is $60 and well worth it. The mount is threaded 8-32 on both sides and mounts through the side rail mounting holes in the receiver. It doesn't use the threads in these holes, the 8-32 mounting screws pass right through. The mount is type 2 annodized and beautifully machined. It is tapered to fit snugly in the receiver and fits so well that the mounting holes just about line themselves up. The mounting system works great. I've tried to think of a better mounting system that picked up the Ring Sight holes, but I haven't been able to. Martin said he wanted to deliver a prefessional quality mount and he succeeded.

The mount comes with instructions, four 8-32x1/2 screws, lock washers for these screws, and one 10-32x5/8 screw. I have CMMG side rails and probably could have used the 1/2 inch long screws, but decided to get 8-32x5/8 inch button head cap screws to account for the added material of the side rails. The best places in the U.S. that I found for these screws are Ace Hardware or Fastenal (Fastenal may want you to buy in bulk, call them first to check). I used blue Loctite on the threads and didn't use the supplied lock washers.

I deviated from Martin's plans a bit and decided to get a special mount Compact ACOG with a M16 carry handle adapter. I had one of the machinists at work drill two extra holes in the mount for me. He used some threaded hole transfer pins to precisely transfer the holes from the Trijicon mount into the msw mount. You don't have to use both holes in the Trijicon mount. I think that mount has two holes to allow you to adjust eye relief. It just worked out for me that I could use both holes, so I did.

I think it all came together great. I now have a fantastic sight at roughly the same height as the standard Ring Sight. My first time shooting with the standard Ring Sight I was averaging 5 inch 5 shot groups at 44 yards. With the Compact ACOG I now have the 5 shot 50 yard groups down to 1 3/8 inch on average. This is shooting SS197SR ammo, off sandbags, with no called flyers.

Here are pictures of the MSW100 and the Trijicon M16 adapter (the silver holes are the ones I had drilled):











Here is the mount in the receiver. It is a pretty tight fit in the back and the M16 adapter is just about as far back as it can go:



Finally done! It may look like there is no clearance under the back of the ACOG, but there is at least 1/8 clearance between the ACOG and the receiver and the clearance looks good:








The 2x20 Compact ACOG I used has a 2.1 inch eye relief, so I had to mount it pretty far back. The 1.5x24 Compact ACOG has a 3.6 inch eye relief and could be mounted further forward and pick up one of the two existing holes in the mount.

I see no reason why the msw mount couldn't be used with any sight that had a M16 carry handle mount adapter available. I know Arms makes adapter mounts for the Aimpoint and the Trijicon TriPower.

If anyone else here is using the msw mount let's see some pics and a little review.

Martin can be reached at [email protected]
 

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Discussion Starter · #2 ·
Here is Martin's PS90 with a 1.5x24 M16 mount Compact ACOG mounted. It looks like it is using regular socket head cap screws, but the kit comes with button head cap screws (rounded head and larger in diameter):





The pic below shows the clearance to the receiver well. It also shows how you can look down the M16 sight hole and use that as a ghost ring if you want too.

 
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