WWSD in 5.7x28mm

[Lu249]

I recently got back from a prairie dog trip in South Dakota. This is an annual trip that me, some family, and some close friends take every year. We usually take a lot of Dakota’s, 40Xs, ruger 77s, CZ 527 in anything from 17 hornet and 20 tactical up to 22-250s and 225 Winchester. I took my WWSD 2020 along just for the fun of it to see how well it would perform. I picked up 240 rounds of Ammo Inc 60 gr VMax at the local gun shop for under $0.75/round and shot them through it. Pretty hot 223 for being factory loads and wicked an prairie dogs. 60 gr at 3050 fps. Besides a few being too tight to close the bolt all the way, they ran flawlessly. And to my surprise and everyone else’s, it shot very good. I was quite impressed. I was running a holosun with a acss reticle and a 6X vortex magnifier. I’ve always wanted to play with 5.7x28mm. I think it’s a neat little round. I would think building a WWSD in 5.7 would be pretty cool (and yes I know Cmmg has their banshee upper in 5.7, I think I can build a better and cheaper one) . I’m my head there’s two options I can go. For both options I would be using my existing KP-15/WWSD lowe and CMMG 5.7 AR-15 mags. I’m also open to suggestions on muzzle devices and optics. Want alittle magnification on it. Thinking maybe a mini ACOG.

Option 1:Leave it as a Rifle: my first option would be to buy a 16.1” barrel and BCG from CMMG and then buy the 13” carbon fiber handgaurd from faxon (I was thinking the 15” but they are sold out everywhere and I’d figured it be a good idea to make the two uppers look different so they don’t get mixed up). I would get better ballistics but it wouldn’t be as handy as option 2 which is to SBR my lower.

Option 2: Make it an SBR: my second option is to file a form 1 for my lower an make it an SBR. If I went this route, I’d do a 8” barrel and bcg from CMMG. The only problem is faxons shortest carbon fiber handgaurd is 10”. I have looked at Coda Evolutions 7” carbon fiber handgaurds which are alittle cheaper than faxing but I’m not sure how they will compare. Would like to hear from anyone if they’ve used Coda before (these faxon handgaurds have really spoiled me lol).


Both options will be about 60-70% the cost of a CMMG upper and I feel I’d get more for the money building it myself. Open to any suggestions.

 

[BigBlue 94]

5.7x28'e downfall is its ammo. Expensive and relatively tough to find on a good day.

I must say it is an intriguing, cute little cartridge though

 

[FL-NC]

5.7x28'e downfall is its ammo. Expensive and relatively tough to find on a good day.

I must say it is an intriguing, cute little cartridge though

I would be interesting in seeing a light bolt action carbine (something like a Ruger American Ranch) in that caliber. Maybe a small compact carry pistol too- like a S&W shield.

 

[citizenconn]

I would be interesting in seeing a light bolt action carbine (something like a Ruger American Ranch) in that caliber.

I've got a few Howa 1500 mini actions each in an Oryx chassis. I've not been greatly interested in that round in its existing firearms except the P90, but I could go for it in an Oryx chassis.

 

[Lu249]

5.7x28'e downfall is its ammo. Expensive and relatively tough to find on a good day.

I must say it is an intriguing, cute little cartridge though

Id probably handload for it. I know thats it’s kind of finicky to load but I’m no stranger to that (I reload for 351 WSL and 219 zipper) That way I can cut cost on ammo to way less than it sells for.

 

[Lu249]

I've got a few Howa 1500 mini actions each in an Oryx chassis. I've not been greatly interested in that round in its existing firearms except the P90, but I could go for it in an Oryx chassis.

Yeah I’ve pondered on buying a PS90 for ever. Very unique and a very cool package but I’m not sure the cost justify that. Especially with the cost of 5.7 as well. Also the triggers are serviceable to say the least. This upper would be like 1/3 the cost of one

 

[citizenconn]

Yeah I’ve pondered on buying a PS90 for ever. Very unique and a very cool package but I’m not sure the cost justify that. Especially with the cost of 5.7 as well. Also the triggers are serviceable to say the least. This upper would be like 1/3 the cost of one

I'm aware of the WWSD guns, but don't know if they are short stroke piston or DI. I would wonder if a 5.7 DI upper would be finicky to get to cycle. But I'm all for you doing it. I am waaaaaay too cheap to buy any FN rifles even though I covet several.

 

[Lu249]

I'm aware of the WWSD guns, but don't know if they are short stroke piston or DI. I would wonder if a 5.7 DI upper would be finicky to get to cycle. But I'm all for you doing it. I am waaaaaay too cheap to buy any FN rifles even though I covet several.

I’m buying the BCG from CMMG, it’s radial delayed blowback. No gas needed. That’s the cool part of it. But the WWSD rifles are DI.

 

[citizenconn]

I’m buying the BCG from CMMG, it’s radial delayed blowback. No gas needed. That’s the cool part of it. But the WWSD rifles are DI.

Sounds like you've got it all planned. Let us know how it works out.

 

[BigBlue 94]

Id probably handload for it. I know thats it’s kind of finicky to load but I’m no stranger to that (I reload for 351 WSL and 219 zipper) That way I can cut cost on ammo to way less than it sells for.

One of the tough parts is supposedly lubing the cases for extraction. But ill bet you can handle it. There is a lot of like 450 cases on proxibid right now for about 10 cents a piece...

 

[N555]

I would try a P50 and "pistol brace".

But direct impingement is a lot easier on the brass than blowback.

 

[Lu249]

I would try a P50 and "pistol brace".

But direct impingement is a lot easier on the brass than blowback.

Yeah but I think it’s blowback as well. And having 5.7 in a more conventional AR platform would be optimal

 

[N555]

Oh P50 is definitely some form of blowback.
The fired brass from the banshee looks like new brass, compared to the blowback guns which visibility stretch the brass.

 

[Lu249]

Update on the 5.7 build. Wasn’t even thinking about the hassle of having to notify the ATF of interstate travel with an SBR so I’ve decided to do the 16” barrel version. It’s also gonna be alittle better anyways to squeeze out some more velocity. Bought a 13” carbon fiber handgaurd and A2 flash hider from faxon (still otw). Bought 2 magazines from CMMG (still otw). Bought the 16” barrel and BCG from KM tactical (still otw). For the optics I was looking for a leupold HAMR but found this bad boy basically brand new for half of retail price on GB. Always wanted an ACOG but didn’t feel like coughing up the dough for it. This was a deal I couldn’t pass up.

 

[Hokkmike]

5.7x28'e downfall is its ammo. Expensive and relatively tough to find on a good day.

I must say it is an intriguing, cute little cartridge though

Also very difficult if not impossible to reload from what I heard. The last know supply I found was at Rural King for $50 a box....

 

[citizenconn]

Also very difficult if not impossible to reload from what I heard. The last know supply I found was at Rural King for $50 a box....

OP says he has the mojo needed to reload this round. Sounds like he has a well-thought-out plan in motion.

 

[Mars5l]

I see today PSA has their 5.7 upper on sale, uses the Fn mag

 

[N555]

I see today PSA has their 5.7 upper on sale, uses the Fn mag

This is the first I'm hearing about this.
Another PSA secret project?

 

[12Bravo20]

The coating on 5.7x28 cases is more to help it feed smoothly from the P90 magazines than it is for extraction. The FiveseveN forum is a great place for information on the 5.7x28.

https://www.fivesevenforum.com/index.php?sid=1a82f37261e3ffa0b6f33a6778db8093

Not counting the coating issues, the 5.7 is very finicky to reload when it comes to powder charges. As long as you pay attention and are careful, then it can be reloaded just fine.

I had one of the older AR57 uppers that uses P90 magazine. It was accurate and reliable. I sold it around 2016-17. Even at that time, 5.7x28 ammo was more costly. Plus the 5.7x28 falls between 223 and 22LR ammo as far as power and range. while 5.7 is a better than 22WMR, it isn't better by much especially considering the cost differences.

 

[N555]

Lots of tests have been done. The coating doesn't appear to do anything for "pistol style mags" that strip the round straight off the top of the mag and stuff it into the chamber.
5.7x28 beats 22wmr in shorter barrels. 5.7x28 out of a pistol is pretty close to 22wmr from a rifle.
Rifle vs rifle the 5.7x28 is between 300 to 500fps faster than 22wmr.

Other considerations:
22wmr burns very very dirty compared to 5.7x28.
22wmr runs very slow 1:16 twist and is barely stabile through a silencer. Small 5.7x28 sized silencers cause 22wmr bullets to tumble after about 10 to 20 feet, been there done that. This was tested in a rifle, a handgun would be far worse. 22wmr needs more like a 5.56mm sized silencer to pass through and remain stable.
5.7x28 fired from a handgun has no problem maintaining stability through a small silencer like the gemtech SFN. 55gr boat tail Spitzer bullets remain stabile all the way down to subsonic when fired out of a handgun through a small silencer such as a gemtech SFN. 60-62gr boat tail spitzer bullets will tumble if fired subsonic through the SFN silencer.

 

[Lu249]

Here is the final build. Specs are:
KE arms slick side reciever and WWSD 2020 lower
CMMG 5.7x28mm 16.1” barrel, BCG, and mags
Faxon 13” Carbon Fiber Handgaurd and A2 flash hider
Geissele super charging handle
Trijicon 4X ACOG

Final thoughts: Have not gotten to shoot it yet but looking forward to it. Wish CMMG made a pencil barrel for 5.7x28 because it is alittle heavier than anticipated (although you can’t blame them as they are basically the only company making 5.7x28 AR barrels) . Also figured the ACOG would add alittle weight as well so can’t complain about the weight too much. Still a very light and handy rifle. Gonna be a fun one for small game and just to plink with.