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The 5.7 x 28 MM stuff







DonTom

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#22
I just now removed the bolt assembly for the first time in my new CMMG MK57 pistol. It is a lot larger than I expected. In fact, it is the same size as the bolt in my Colt SP-1 AR-15 Rifle. The top on the photo below is my Colt SP1 bolt assembly. Below it, is my new CMMG MK57 bolt. The bolts are different for other reasons, of course, but the length isn't one of them:


bolts.JPG

-Don- Reno
 
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DonTom

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#26
I picked up my new Excel Arms MP-5.7 yesterday. I have not yet fired it, but here is some info on it, such as how it compares in some ways to other 57 stuff.

The Excel 9 round magazine is NOT compatible with FN pistol magazines The Ruger 57 stock 20 round mag is also not compatible with the FN (20 round, 30 if after market) pistol mags. But CMMG MK57 is compatible with the FN pistol mags.

The Excel is as hard as hell to get more than 3 rounds in its magazine, unless the tool is used that comes with it. However, with their tool (two of them are supplied) it is VERY easy to get all seven more rounds in after the first two rounds are put in without the tool. The first two rounds must be put in before the tool can be used, and it is very easy to put in the first two rounds. So it's very easy to get in all nine rounds as long as you have the small tool with you. Without the tool, I can get in six rounds max, but with great difficulty. They get progressively more difficult after inserting two rounds.

There is a dot on each side of the rear sight, but no mark on the front sight. I would like a dot on the front also--perhasp I will paint my own.

See the magazine tool in the lower photo below:

The pistol itself is a bit on the heavy side (54 oz.), but not too bad, and it looks fairly well built. ExcelMP57.JPG MagTool.JPG

-Don- Reno
 
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DonTom

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#27
I have a 5.7x28 setup on my 550. Works pretty damn well.
I have never tried reloading ammo. Perhaps I will get into it, but I really don't even know where to start.

I heard in the past that 5.7 x 28 MM is difficult to reload. Has something hanged?

-Don- Reno
 

Kinoons

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#28
I have never tried reloading ammo. Perhaps I will get into it, but I really don't even know where to start.

I heard in the past that 5.7 x 28 MM is difficult to reload. Has something hanged?

-Don- Reno
It’s not difficult in and of itself, but it is a little labor intensive.

You’ll have to use a single stage or turret press unless you want to pay for the custom shell plate from elite ammo for the 550. No other progressive systems are supported last I checked.

.45acp and 9mm are stupid simple to reload. You clean the brass and run it through your press. Pay attention to your powder loads and you’ll be just fine.

For 5.7x28 you have to clean it in a special manner. Resizing and trimming must be performed nearly every time you load a case as it’s a bottlenecked case.

The fiveseven pistol and PS90 are separate systems. To optimize the loads you have to have separate rounds for each. If you load hot for the pistol you cannot use that ammo in the carbine. If you load for the carbine you’ll lose performance out of the pistol.

I wouldn’t have 5.7x28 be the very first round I tried to load. Put together some 9mm or .45 to get a feel for the process and the attention to detail for each step in the process. Once you have a good idea how reloading works you can step to 5.7 and do so safely.
 

DonTom

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#29
Here is how the CMMG MK 5.7 compares to the PS-90.

BTW, I find the pistol arm brace works very well for me as a rifle stock when extended. No need to register it into a SBR, which I was considering. I am glad the ATF clarified that issue about using a pistol brace as a rifle.

-Don- Reno
 

DonTom

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#31
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DonTom

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#32
Now I will have to decide if I want to put the binary trigger in the rifle or the pistol.

It will probably make more sense to do the rifle, as I will need to build up an AR-15 lower receiver anyway, or I can use my fake M-16 and use the "full auto" marking for binary. It's a NDS-16A1 lower, all marked as a M-16, including a fake "AUTO" position. Legal, but it fools 99% of those who look at it thinking it's the real M-16. The "M-16A1" markings is in a different font than the "NDS-16A1" markings, which makes it legal.

OTOH, I might even be better to start out with a blank lower receiver so I have nothing to remove to drop in the binary trigger.

-Don- Reno
 

Kinoons

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#33
A better thread for your claim - the banshee is uniformly better than the P90?

Banshees have a 5-8” barrel depending on model. My p90 has 10”. Better ballistics.

P90 is 19.9” long. The banshee 100 is 23.9”. So at best it’s a draw (with half the barrel) or the p90 is shorter.

A p90 gets 50 rounds per mag. A banshee only gets 20-30. Easy P90 win there.

A p90 is truly ambidextrous.

I will concede that a banshee is lighter.

For me it’s a no brainer - a banshee is cool, if I had the spare coin I’d buy one, but from a war fighting perspective a SBRed p90 is the way to go.
 

DonTom

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#34
Banshees have a 5-8” barrel depending on model. My p90 has 10”. Better ballistics.
Don't you mean PS-90? A P90 has full auto and is too new to be registered as a Class 3.

I have a Banchee upper coming in soon. They make it in several sizes. I will soon have a 16.1" rifle barrel and it will use 40 round 5.7 mags that will fit into a AR15 lower. It's what I will put my binary trigger in. I already have the lower receiver put together with the binary trigger.

The Bachchees are also 100% ambidextrous. So is the safety on my binary trigger, so I will not lose that feature by going binary.

Banshees have a 5-8” barrel depending on model. My p90 has 10”. Better ballistics.For me it’s a no brainer - a banshee is cool, if I had the spare coin I’d buy one, but from a war fighting perspective a SBRed p90 is the way to go.
I was tempted into registering and making my Banchee pistol into a SBR, but I decided on simply buying the Banshee rifle upper instead and keeping it at 16.1".

-Don- Reno
 
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Kinoons

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#35
Don't you mean PS-90? A P90 has full auto and is too new to be registered as a Class 3.

I have a Banchee upper coming in soon. They make it in several sizes. I will soon have a 16.1" rifle barrel and it will use 40 round 5.7 mags that will fit into a AR15 lower. It's what I will put my binary trigger in. I already have the lower receiver put together with the binary trigger.

The Bachchees are also 100% ambidextrous. So is the safety on my binary trigger, so I will not lose that feature by going binary.

I was tempted into registering and making my Banchee pistol into a SBR, but I decided on simply buying the Banshee rifle upper instead and keeping it at 16.1".

-Don- Reno
I have a PS90 that’s SBRed. Sorry for the confusion. For size and weight purposes it’s the exact same size as a P90 but without the full auto.

I don’t believe that a banshee is 100% ambi as it does side eject. For some people that’s very distracting when on the left shoulder. Perhaps that’s more a training issue but it is there. A PS90 ejects direcly down into a nice neat pile.
 

DonTom

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#36
I don’t believe that a banshee is 100% ambi as it does side eject. For some people that’s very distracting when on the left shoulder. Perhaps that’s more a training issue but it is there. A PS90 ejects direcly down into a nice neat pile.
True, I forgot about that, as I am right handed.

BTW, the AR74 holds the ejected cases into a bag that is mounted on what would be the magazine well on an AR-15 lower receiver.

I have not fired my PS90 for a long time, so I even forgot how it works!

-Don- Reno, NV
 

Kinoons

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#37
True, I forgot about that, as I am right handed.

BTW, the AR74 holds the ejected cases into a bag that is mounted on what would be the magazine well on an AR-15 lower receiver.

I have not fired my PS90 for a long time, so I even forgot how it works!

-Don- Reno, NV
Yeah I’ve looked at the AR 57 in the past. I’ve seen guys put bags on the bottom (or hollowed out AR mags) to catch empties. The bag is good for the range, not actual “duty” use.

the big question becomes once you go to the AR form factor, why not shoot 5.56? You’re taking the size and weight of a 5.56 firearm but you want the reduced performance of the 5.7 round? There are no situations that makes sense to me.

Well I guess you could say you want the ergo’s of an AR because you normally shoot an AR, but you know your engagement is going to be inside 50 yards in an area where overpenatration of stray rounds is a real problem, then a banshee can make some sense. AR 57 less so since it uses PS90 mags. For me, in that specific situation, the PS90 shines.

I’m all for more 5.7x28 guns. More platforms means more and less expensive ammo for all of us. I think the 5.7x28 is a great backpacking round and should replace 22lr and 22mag in the ultra lightweight backpacking/survival segment. It’s the cost that has prevented me from keeping a 5.7x28 based firearm in a go bag. Hopefully ruger is changing this by jumping into the market. I really want to see a 10/22 takedown style rifle from ruger chambered in 5.7x28. Give me the 16” barrel in a normal traditional stock at a 4.5 lb weight, 10rd rotary mag? I’m totally in!
 

MAC702

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#38
...the big question becomes once you go to the AR form factor, why not shoot 5.56? You’re taking the size and weight of a 5.56 firearm but you want the reduced performance of the 5.7 round? There are no situations that makes sense to me.

Well I guess you could say you want the ergo’s of an AR because you normally shoot an AR, but you know your engagement is going to be inside 50 yards in an area where overpenatration of stray rounds is a real problem, then a banshee can make some sense. AR 57 less so since it uses PS90 mags. For me, in that specific situation, the PS90 shines...
Maybe same reason for 9mm over .45: magazine capacity.

My big question is, how is the bullpup trigger on it?
 

Kinoons

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#39
Maybe same reason for 9mm over .45: magazine capacity.

My big question is, how is the bullpup trigger on it?
30 vs 50 is a far cry from the debate between 9 and 17. There is also the age old caliber debate - but all handguns suck. 5.7x28 out of a rifle sucks less, and 5.56 even less so. Still there are those who say 5.56 is underpowered. Well If that’s the case then 5.7x28 is a squirt gun.

The trigger on a PS90 is okay. More accurately it’s a decent bullpup trigger but nowhere as good as a well tuned AR or pistol. However for 50 yard shots it is more than adequate.
 

DonTom

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#40
the big question becomes once you go to the AR form factor, why not shoot 5.56? You’re taking the size and weight of a 5.56 firearm but you want the reduced performance of the 5.7 round? There are no situations that makes sense to me.
More rounds to fire in smaller magazines with a bit less noise and the same round for smaller pistols and riffles are the only legit reasons I can think of. But I also have AR15s as well as many types of 22's to fire. In handguns as well as rifles.

While there are AR15 pistols that use the .223 / 5.56, I have never seen a small AR15 pistol.

Isn't the 5.7 by 28 MM the thinnest center-fire round? That's probably the main reason why I like it.

I don't expect to use it in combat! But I do have 500 rounds of the military & police (FN red box SS198LF) ammo for it, that I never expect to open.

I also have around 850 rounds of sporting ammo (Blue Box FN SS197SR) to waste with my new binary trigger. @ Sixty cents per round for when I am in the mood of wasting a few bucks out at the range.

-Don- Reno, NV