AR57 Pistol: A short review & praises for Magpul MBUS sights

[mythaeus]

After doing some research on the PS90 and kept an eye on the market for PS90-related stuff, I found a gentleman in Idaho selling 4 PS90 mags and 850 rounds of 5.7x28mm for $400! At about the same time, someone on ARF.com was selling a new AR57 pistol/SBR upper for about $100 less than any retailer online. Having 2 complete RRA pistol lowers sitting around naked, I sold one and proceeded with the AR57 purchases. I soon realized that the upper doesn't some with any sights, with great curiosity of the new MBUS, I found a good deal on the pair for $80/shipped.

Got the upper in the mail, installed the sights, slapped in onto the RRA pistol lower and headed to the range yesterday. Wooooow...I was thoroughly impressed. The complete gun was light weight, recoil was minimal, and it's extremely accurate. Unfortunately, my range doesn't go any further than 50' so I'll have to wait to hit an outdoor range for better assessment. My wife and I shot 100 rounds through and had 2 jams earlier on. The bolt was dry so I oiled it up a little and the rest ran perfectly fine.

If you're not familiar with the AR57, it's an upper variant that takes PS90 magazines and uses standard AR15 lowers. The mag is loaded on top of the upper receiver and the spent casings are dropped down through the lower's mag well. I use a gutted Lancer 30-rd clear mag as a brass catcher. The mag holds all of the 50 spent casings. For now, I have to hold it in place with my weak hand, but I'll be cutting off the protruding part of the mag so that it will lock in place (the AR57 upper bolt fits flush with the top of the lower so standard AR mag won't go all the way in). One thing though, the opening end of the casings gets dented pretty good. All of the shell are squared off on one edge. I'm not sure if that is the case for PS90 as well or just the AR57 upper.

I was as impressed with the MBUS sights as I was with the AR57. I don't care for the way they look on the upper, sort of curved and unflushed, which breaks the aesthetic lines (IMHO) of the gun. However, the sight picture is great and targets are easier to acquired compared to the Matech and other A2 style sights I have on my other guns. I think the fact that the width of the sights are wider makes it easier to find center (not sure if that makes any sense). What I mean is that with the skinny Matech, you only have 1 point of reference to align your eyes. The left edge, right edge, and peep hole creates a 3 points of reference making it easier for the brain to find the alignment point better. OK, maybe it was just in my head, I don't know. Anyway, now I'm thinking of getting a few more sets to replace my other sights.

Oh, one minor thing. I replaced the standard grip with a Magpul MOE grips. Nothing to write home about, but it worth noting that the grip was comfortable, fit both of our hands well, and not having the standard AR15 grip's bump is a nice feel.

Here are a few shots of this fine baby:









Al

[thejeanmachine16]

cool gun...... never heard of it , learned something new today

[Asmodeus6]

Is there room to cut a new "notch" in the side of the mag above the old one? That's what I would do. Take a USGI mag body and just cut a new square above the old one. It will lock in with less mag in the magwell and you won't have to cut the top of the mag off.

Are the dents at the case mouth or on the rim? Or are they flat as in one whole side of the casing is smashed flat?


Some people were real big on the 5.7 because of the way it penetrates, and because of the capacity of the 5.7 pistol. Then they neutered the ammo available for sale to Joe the consumer... and it's still pretty spendy for what it is. I'd never do a 5.7 upper for an AR. But as a pistol, I think what you have makes the package pretty attractive. 50 round capacity, with a "catcher" and in a small-ish package. It's a low recoil round so as a pistol that might be the perfect setup for 5.7. Kinda makes me want one!

[mythaeus]

Is there room to cut a new "notch" in the side of the mag above the old one? That's what I would do. Take a USGI mag body and just cut a new square above the old one. It will lock in with less mag in the magwell and you won't have to cut the top of the mag off.

Are the dents at the case mouth or on the rim? Or are they flat as in one whole side of the casing is smashed flat?


Some people were real big on the 5.7 because of the way it penetrates, and because of the capacity of the 5.7 pistol. Then they neutered the ammo available for sale to Joe the consumer... and it's still pretty spendy for what it is. I'd never do a 5.7 upper for an AR. But as a pistol, I think what you have makes the package pretty attractive. 50 round capacity, with a "catcher" and in a small-ish package. It's a low recoil round so as a pistol that might be the perfect setup for 5.7. Kinda makes me want one!

I've thought about cutting a notch, but I'll have to do that on the Lancer since I want to be able to see the spent casings (just in case I want to dump them out early, and the cool factor). I'll think about it though.

The dent is along the mouth on one side. Imagine taking a spent casing, tilt it 45 degrees and a crush one side again a hard surface.

I was debating between a rifle upper and a pistol upper. The main reason why I went for the pistol upper is because I have a spare pistol lower , but it worked out well. 5.7x28mm actually costs the same or less than brass .223.

Al

[mojo]

Wow Al ... that's very nice. I really like the look of that upper. I've never seen a short 5.7 upper, only the rifle ... man that's all I need is to add something else to my "wish" list.

Very nice build!

[mythaeus]

Wow Al ... that's very nice. I really like the look of that upper. I've never seen a short 5.7 upper, only the rifle ... man that's all I need is to add something else to my "wish" list.

Very nice build!

Thanks bro! I cheated. Didn't build it, just bought the lower complete and same for the upper.

BTW, I am not impressed with the finish on the RRA lower. You can see in the photos that it's a bit duller than the upper. Compared to my other lowers (S&W, EA, DPMS, and Sun Devil), RRA is dead last in the finish department. The fit is perfect though.

Al

[mythaeus]

Oh, just to give you an idea of the recoil, check out the video that my wife took for muzzle flash comparison (another thread):



I have another video of my wife shooting, but haven't had a chance to youtube it yet. That one shows the recoil a lot better.

Al

[LisaA]

Still drooling over the guns in your other thread. Very nice.

[mythaeus]

Still drooling over the guns in your other thread. Very nice.

Hehehe...you know that you're welcome to try out any of them anytime Lisa.

Al

[jcabin]

Awesome I never saw that before. I'm a big fan of the original gun.