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RDTCU
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Posted: 2/15/2009 7:37:06 PM
[Last Edit: 6/14/2009 2:26:09 PM by RDTCU]
My first AR pistol is finally done!
Operating system similar to a ZM LR-300. It fires and cycles 5.56 every time. Forward charging handle. 80% lower. And yes, no buffer tube.
More Info and pictures HERE

New Pictures:

http://i241.photobucket.com/albums/ff206/devtucker/AR%20Pistol/DSCN0441.jpg
http://i241.photobucket.com/albums/ff206/devtucker/AR%20Pistol/DSCN0445.jpg
V8Astro
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Posted: 2/15/2009 8:32:42 PM
damn nice job. Looks like fun!
Shoot-To-KIll
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Posted: 2/15/2009 8:46:12 PM
Awesome! have any in progress pics?
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LGK
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Posted: 2/15/2009 8:59:48 PM
nice
OhioShooter1975
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Posted: 2/15/2009 9:08:17 PM
Very nice looking gun there!
cookhj
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Posted: 2/15/2009 9:14:16 PM
interesting recoil system you got there. would be interesting to see other rifles/pistols built in that style.
RDTCU
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Posted: 2/15/2009 9:20:34 PM
I'll didn't take that many pics during the build, but it went through a few changes throughout the process.
More pics added to the album in the original post!

http://i241.photobucket.com/albums/ff206/devtucker/AR%20Pistol/DSCN0343.jpg
http://i241.photobucket.com/albums/ff206/devtucker/AR%20Pistol/DSCN0344.jpg
RDTCU
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Posted: 2/16/2009 12:23:01 PM
[Last Edit: 2/16/2009 12:46:16 PM by RDTCU]
Update, let the little sister shoot it, and she loved it...
You don't pick up on the echo with the earmuffs on, but if you're just using your hands and drop them after the shot, it's ridiculous. The conical brake definitely tames the blast to the shooter, but does nothing for the fireball you get with cheap ammo...
RDTCU
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Posted: 2/16/2009 11:54:18 PM
upl8te
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Posted: 2/17/2009 12:49:02 AM
[Last Edit: 2/17/2009 12:50:32 AM by upl8te]
Is that your design? Would you feel like showing more of the design?
bgoodjohnny
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Posted: 2/17/2009 3:05:09 AM
Beautiful. Sturdiest looking piston I've seen on an AR. Does the charging handle move with each shot?

Nice work!
-Johnny
RDTCU
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Posted: 2/17/2009 8:15:20 AM
[Last Edit: 2/17/2009 10:48:44 AM by RDTCU]
upl8te,
The lower is a standard 80% lower finished to spec, sans buffer tube. I machined the rear plug from SS roundstock. The upper is a DPMS slick flattop with the gas tube hole opened up for the larger gas key. The bolt carrier was a Bushmaster spare i had, chopped behind the firing pin and cleaned up with a lathe grinder. The barrel was a cheap (but accurate enough) Dez Arms 10.25 pistol barrel that came with a carbine sized gas port which had to be opened. The forened is a bushmaster carbine forend clearanced for the recoil system, the barrel nut also had to be clearanced. Gas key tube and gas tube are chromed, hardened die cast ejector sleeves, scraps from work. The gas block is a MI upper height rail block, with the gas tube hole bored offset and plugged. The SS muzzle brake is my own design, made from round stock (2 pieces, with the outer lip roll formed around the end). Next time i disassemble it (for duracoat) i'll be sure to take more pictures of the components.

bgoodjohnny,
Technically it's not a piston, it's a DI system with an extended gas key and a straight gas tube. I think a true piston would be too violent for the shortened bolt and would lead to bolt tilt and receiver wear. The beefy gas tube and gas key function as somewhat of a guide rod as well to reduce bolt tilt. Also, the charging handle is non-reciprocating and has a latch similar to a standard AR charging handle to keep it in place while the action cycles. I don' t know that i would want something reciprocating at high speeds if i were to put my thumb up the side of the handguard...
JoshAston
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Posted: 2/17/2009 8:33:33 AM
I want one, but SBR'ed with a folding stock.
I'm from Texas, what country are you from?
upl8te
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Posted: 2/18/2009 6:13:01 PM
Originally Posted By RDTCU:
upl8te,
The lower is a standard 80% lower finished to spec, sans buffer tube. I machined the rear plug from SS roundstock. The upper is a DPMS slick flattop with the gas tube hole opened up for the larger gas key. The bolt carrier was a Bushmaster spare i had, chopped behind the firing pin and cleaned up with a lathe grinder. The barrel was a cheap (but accurate enough) Dez Arms 10.25 pistol barrel that came with a carbine sized gas port which had to be opened. The forened is a bushmaster carbine forend clearanced for the recoil system, the barrel nut also had to be clearanced. Gas key tube and gas tube are chromed, hardened die cast ejector sleeves, scraps from work. The gas block is a MI upper height rail block, with the gas tube hole bored offset and plugged. The SS muzzle brake is my own design, made from round stock (2 pieces, with the outer lip roll formed around the end). Next time i disassemble it (for duracoat) i'll be sure to take more pictures of the components.

bgoodjohnny,
Technically it's not a piston, it's a DI system with an extended gas key and a straight gas tube. I think a true piston would be too violent for the shortened bolt and would lead to bolt tilt and receiver wear. The beefy gas tube and gas key function as somewhat of a guide rod as well to reduce bolt tilt. Also, the charging handle is non-reciprocating and has a latch similar to a standard AR charging handle to keep it in place while the action cycles. I don' t know that i would want something reciprocating at high speeds if i were to put my thumb up the side of the handguard...


Thank You for the info.
bgoodjohnny
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Posted: 2/19/2009 1:07:31 AM
Coolest. Build. Ever.

Thanks for the answers, you've given me something to think about in my spare time.

-Johnny
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Posted: 2/19/2009 1:25:25 AM
totally f'ing awesome!
Texaspyro21
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Posted: 2/19/2009 1:35:51 AM
I suggest filling a patent on the design and finding someone who will buy the design from you. Could be some big money since Para is getting like $2500 for theirs.
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RDTCU
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Posted: 2/19/2009 8:20:45 AM
[Last Edit: 2/19/2009 8:28:14 AM by RDTCU]
I've seriously considered a patent, the one hangup is that the gas system is already patented by ZM/YHM/Para (as far as i know), and my forward charging handle will only work on that type of system, if you're planning to lose the stock. Don't know many people that will drop $1500plus on a ZM upper just to have someone they don't know hack it up just to move the charging handle... If you're keeping the stock, i suppose it could be adapted to work with a piston system, i'll have to give this some thought. Thanks for the encouragement and suggestions!
buckmeister
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Posted: 2/19/2009 8:38:08 AM
I picked up a ZM bolt/carrier some years back, hoping to do something similar. The ZM extended key rides higher than the standard, so the hole through the receiver is offset higher. The channel in the upper where the key rides, must also be deeper than the normal upper. The ZM charging handle is correspondingly different. My thoughts as to why ZM's setup is "taller" than the norm, may be that they wanted all of this to clear a standard barrel nut.

I have a DPMS upper with more meat on the top, in hopes it can be machined to accept the ZM carrier. Looking at your mod, it may be more effective to mill the key's base down so the axis lines up more with the normal setup.

... or RDTCU, since I have a shortened carrier, wanna make a "Rhino" honker for me?

buckmeister
RDTCU
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Posted: 2/19/2009 8:58:18 AM
[Last Edit: 2/19/2009 8:59:42 AM by RDTCU]
buckmeister,
As in .470 Rhino???
or a Rhino piston system???

Anyway, the gas key i used is shorter than a ZM setup, but the bushmaster barrel nut had to be significantly clearanced, but not so much as to compromise strength. If i was worried about it i could turn out a steel nut to replace the aluminum one. I also had to mill a shallow groove in the charging handle slot in the upper to clear the gas key where it sits, because i could not take the key any lower. As far as i know, ZM uses a proprietary barrel nut, as their forends are model-specific and a standard forend will not work. You didn't happen to grab a ZM gas block while you were at it, did you? The gas block/gas tube will give you some trouble and will have to be fabbed from scratch if you don't pick up a ZM one. I would also recommend using your high upper just for simplicity's sake, 'cause if you go much lower, you open up a whole can of worms with clearance issues, i just wanted to see if it could be done.
Just a note, my bolt is slightly shorter than a ZM, so the buffer plug would have to be a little longer to permit it to lock back...
Thanks for the interest!
RDTCU
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Posted: 2/19/2009 7:00:12 PM
Took it to the range today, and i was completely suprised. I'm using a 4moa Burris Fastfire dot sight (pretty much a 25yard pistol sight) so sighting it in at 100 yards was.... touchy. Using a rest, some of my groups were surprisingly small, around 3" 5 shot groups. the last few groups were all in the 5" ring with one or two fliers. I was amazed since the dot covers up half the 8" target and i have no stock. Only complaint is the standard mil-spec trigger, of course, but i didn't anticipate it being so consistent to begin with, or i might have dropped on a better trigger! A couple people at the range were commenting so i let them pop a few off and they got a kick out of it.
buckmeister
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Posted: 2/19/2009 10:54:00 PM
I'll take one "Rhino" DI extended key, please. I have a DPMS Hi-Rider Flattop Upper Receiver. Missed out on the ZM gasblock.

You are correct, the ZM key is longer (semi-midlength). The carrier has remnant "ears" which make it longer than yours. I like the ZM spring keeper, which you incorporated on your version. I have a Badger railed forend with a barrel nut arrangement I think would work (too bad its a carbine length "tube"). Details on you charging handle would be welcome.

buckmeister
RDTCU
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Posted: 2/22/2009 1:06:30 AM
[Last Edit: 2/22/2009 1:10:08 AM by RDTCU]
buckmeister,

Took it down for blasting and Duracoat.
More pics added to show the charging handle assembly...
ALBUM

http://i241.photobucket.com/albums/ff206/devtucker/AR%20Pistol/DSCN0358.jpg
http://i241.photobucket.com/albums/ff206/devtucker/AR%20Pistol/DSCN0356.jpg
KELBEAST
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Posted: 2/22/2009 7:58:18 AM
It never made sense to me why people go to piston systems if they're going to keep the buffe/spring etc in the stock. They might as well just do up a system like this, or like the Olympic OA93 system and eliminate the buffer tube assy completely.

PS this would be really cool with a tax stamp and a side folding stock!
RDTCU
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Posted: 3/1/2009 7:22:32 PM
Tony-Ri
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Posted: 3/5/2009 5:09:29 AM
[Last Edit: 3/5/2009 5:15:26 AM by Tony-Ri]
I like how you took the hardest part of finishing the 80% and turned it into a starting point for a unique design.

The BCG assy looks like an AK raped an AR and that's the demon spawn...

How did you make the ultra-extended key, and where exactly is the return spring? Ok, I see it now under the handguard.
Home schooling doesn't make you socially inept, it just makes you awesome enough to do shit people remember centuries later. ~ Frost7
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