Thought about getting one but I was a bit reluctant and seems I completely missed that boat. I much preferred the looks of it with the ZM weapons pistol grip. I would still like to get one of those grips.

Don't know anyone who owned one or took one apart for gunsmithing. An interesting concept. If it would have been cheaper it could make a good trunk gun at the least. Never heard any complaints about them.

Wasn't a piston.  It was a modified DI where the gas tube was attached to the carrier and functioned as the action rod. The concept still reduced gas blowback.

I think the companies selling them had a lot to do with their demise. They always seemed to be interested in LE sales and not much interest in civilian sale. I tried a few times over the years to get them to sell me a short barreled upper for a pistol, but they flat refused each time.

Also, as far as ARs go, this was one of the least modular.

Yikes.
Reads like the worst of both worlds.

Respectfully, we could banter semantics about what type of system it is, but it does use a gas piston/operating rod, just an earlier (than most of the current AR piston designs) and slightly different (hybrid?) version that the inventor chose to call a "delayed gas impingement" system. The long "gas tube" that is bolted to the top of the bolt carrier, where the gas key would normally attach, is actually a really long operating/push rod. I personally think that it's a cool design regardless...YMMV.

Here are a couple of good links about the gun, and the actual operation of the system:

http://www.m4carbine.net/showthread.php?61086-Para-TTR-ZM-LR300-requesting-pics-and-opinions

http://www.weaponeer.net/forum/forum_posts.asp?TID=11144&PN=1

And here is a link to an older thread from here in the hive:

http://www.ar15.com/forums/t_3_118/507832_PARA_TTR___ZM_WEAPONS_LR300_what_do_you_guys_think_of_it___.html

The link below has some interesting info, straight from the designer, and some discussion from Todd Jarrett as well. The old Para videos of Todd Jarrett shooting it and demonstrating its almost complete lack of recoil were very cool, if you can still find them somewhere.

http://www.tactical-life.com/gear/para-usa-tactical-target-rifle-556mm/

And here is another "interesting" link...

http://avtomat-pistolet.com/z-m-weapons-lr-300-para-usa-ttr/

And the obligatory Wikipedia link, with excerpt below:

http://en.wikipedia.org/wiki/LR-300

"The gas key is extended beyond its normal length to form an operation rod, such as an M14 or AK47, extending into the top of the forward handguard. The gas key contains the return spring which is fixed between the front of the receiver and the collar at the front of the gas key. The gas tube runs backwards from the gas block in the front sight base and enters the gas key. In this way when the firearm fires at least some of the combustion gases from inside the gas tube are vented into the handguard area rather than the receiver. This means the standard buffer assembly is not required at the rear of the weapon, allowing a folding stock to be fitted to reduce the overall length of the weapon."

And for anyone who cares, here is the brief historical version of, Para gets into the Black Rifle business...

http://www.thefirearmblog.com/blog/2008/08/26/para-ordnance-ttr-ar-15/

http://www.pagunblog.com/2008/08/24/para-ttr-ar-15/

...and Para gets back out...

http://www.thefirearmblog.com/blog/2011/10/03/para-usa-exits-rifle-market/

Personally, if the people selling the remaining models were not clinically insane, see the link below, I would personally like to own one of these, if only for personal amusement and posterity's sake.

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=465297956

I wasn't slamming it, I obviously wanted one since I contacted ZM more than once trying to get one, BUT it's still not a piston, and that's not semantics.

There was no separate piston in the gas block, or anywhere else other than the bolt that was pushed by gas bled from the barrel down a gas tube just like any standard DI AR.  And that's not a "push rod" but a beefed up gas tube that doubled as a spring guide rod that wasn't "pushed" by a piston but rather pulled by the bolt carrier.

More than one of the links you provided cover the same details.

Now, if RDTCU comes in here and says its a piston, I'll change my opinion.

I didn't think you were slamming, and I wasn't either, LOL.
But...Tomaito, Tomahto, Potaito, Potahto...and yep, we both want one.

And if you want an 11.5" SBR setup...

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=466101459

 

I remember wanting a ZM back in the day but the price was rather high. I'd be interested in one now but spare/replacement parts would concern me.