New possibilities for the 5.7? A gas piston driven 5.7 ?

Discuss rifles chambered for the 5.7x28mm; P90, PS90, and AR57.
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What does your brain think about a piston 5.7 AR??

Amazing, Love it
4
57%
Notttt Sureeeee/ Wrong thread/ Bi curious
0
No votes
Nahhhhhhh, bad idea
3
43%
 
Total votes: 7

Piston Driven
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New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by Piston Driven » 04 Jun 2012, 22:59

New here, but just wondering what the 5.7 world thought of a a new 5.7 layout? Gas piston? Don't get me started on DI, Ive already teared up enough AR forums !! In theory though you could modify a standard PMAG or STANAG magazine to fit a 5.7 and get aprox 5-7 more rounds? So then you could just use a AR lower of your desire and just get a upper ? Interesting in theory, but let me know what y'all think, feed back, thoughts, feelings??? :ponder:

Fallschirmjäger
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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by Fallschirmjäger » 07 Jun 2012, 18:33

Well you could possibly put a block in a PMAG to account for the shorter length of the x28 compared to the x45 cartridge, but then you'd have to have a new follower, and very likely a new spring. In terms of diameter at the base you can fit 35-36 rounds of 7.90mm rim diameter 5.7 within the same length as 30 rounds of 9.58mm rim diameter 5.56, but the rounds have different tapers which might affect feeding (STANAG magazine is curved to accommodate the 5.56 whereas the FN magazine is straight to accommodate the 5.7.

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Esteves
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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by Esteves » 07 Jun 2012, 18:49

For magazines, there seem to be three basic camps:
1) Modify AR magazines (no savings in bulk of load, no interoperability with pistol)
2) adapter/mag-well that accepts custom magazines or modified M1 carbine magazines (no interoperability)
3) adapter/mag-well that accepts FsN magazines
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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by Piston Driven » 09 Jun 2012, 16:01

Im not saying for me to personally do (maybe if its safe enough) but it would seem very easy if you had your own CNC shop or company. :thumb:

SamM
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Colt MARS

Post by SamM » 17 Jun 2012, 08:06

Remember the Colt MARS project from back in the late 80's and early 90's? Why not cutdown an AR15 lower to fit the FN FiveseveN magazines? Those mags can be converted into 30 rounders pretty easily. You could then miniaturize the upper and gas piston system. Use a pistol length system and SBR the rifle for use as a PDW. I'd love to have one to go with my pistol.

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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by fooschnickens » 17 Jun 2012, 08:20

Would the 5.7 round have enough gas pressure to operate a piston system (or even DI)? I think there's a reason pretty much any pistol caliber AR you see is direct blowback. Granted piston systems can run on a lot less gas, it'd have to be a reeeeeeeeeeeeeeeeaaaaaaaaaaaalllllly short piston. Probably shorter than the SCAR's.

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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by Esteves » 17 Jun 2012, 09:11

Member 22_boomer has already converted an AR to 5.7x28mm and to operate with the FiveseveN magazines. His conversion operated via DI, and he says that it works with both commercial ammo and his handloads.

The MARS did have some size/weight advantages compared to an OTS AR, but some of the changes were pretty drastic (involving cutting and welding) involved fundamental changes in certain standard dimensions, and would be counter to keeping costs down. MGI's Hydra could probably get close, but they've been entirely unenthusiastic every time I've mentioned it.
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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by srt-4_jon » 17 Jun 2012, 10:55

fooschnickens wrote:Would the 5.7 round have enough gas pressure to operate a piston system (or even DI)? I think there's a reason pretty much any pistol caliber AR you see is direct blowback. Granted piston systems can run on a lot less gas, it'd have to be a reeeeeeeeeeeeeeeeaaaaaaaaaaaalllllly short piston. Probably shorter than the SCAR's.
ron williams just released a 9mm DI ar to go along with his 7.62x25 di and 45acp di uppers. companies went blowback because they didnt want to take the time to figure it out.

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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by fooschnickens » 17 Jun 2012, 11:17

I guess it's one of those things where you have to take a step back and really ask yourself "does this make it any better?" Does DI/piston have any great advantages over blowback setups for pistol calibers? Not asking to stir up a sh*tstorm, just ignorant as I have no experience with pistol caliber carbines in general.

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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by srt-4_jon » 17 Jun 2012, 12:08

absolutely. its much cleaner, much less weight, and less recoil. the whole thing weighs more and recoils more than a 223 ar. I cant wait to get one so i can ditch my 9mm blowback ar.

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Re: New possibilities for the 5.7? A gas piston driven 5.7 ?

Post by Piston Driven » 17 Jun 2012, 16:00

:clap: I think you could make a finely tuned piston, put in a upper and have AR mil spec mags in 5.7 (with a couple extra rounds 7.9mm vs 9.6mm rim diameter ) which would be the best of both worlds. Some of the major limitations of the AR 57 and P90 is the 50rd magazine which forces a longer rail system, so anything less would be foolish and kinda dumb (but AR 5.7 have and just say to put a silencer on it... Thats kinda cool...) but you really can't have a designated AR style PDW with 50 rd magazines, and it would just make sense to adjust the .223 mags to 5.7. I think if anyone could pull it off, it would be pretty amazing!

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