I bought a new Sabre Defense Industries rifle with a polymer lower, based on the proven CAV-15 MkII one piece lower.  It is the SDI XR-15A3 Light Weight, $999 bought locally. SDI may not be a household name yet but the small company was just awarded a US Military contract to supply M16A3's for our troops (these would have "conventional" select fire lowers), joining the elite club of Colt and FN as M16 suppliers.

It has the advantages of being extremely tough, very light weight (6.0 lbs with 16" medium barrel), impervious to the elements, minimalist, ergomonic, sleek, comfortable, inexpensive, and multi calibre (lower can accept .223, 9mm, and 45ACP double stack mags).  CAV-15 owners universally love their polymer lowers.  The upper is all SDI (aluminum alloy and steel).  The upper/lower fit is very tight with zero play.  The lower uses advanced materials technology: glass-filled Nylon 6 polymer with vibration welding.

The integrated design eliminates over a dozen parts and requires only three new (inexpensive) ones: longer takedown/pivot pins and a generic roll pin for the buffer retainer.  Fewer parts to fail and break.  No more friggin' castle nuts! The buffer tube is molded into the stock and takes a carbine buffer/spring.

Once I undercut the trigger guard a bit and added a slip-on Hogue Handall, the grip is the best feeling AR grip I have ever experienced.  the integral stock is A1 length for a perfect length of pull of 13".  It points and handles extremely well with its light weight and solid feel.  No stock rattle or annoying seams.  The barrel is a 1/9 5.56 NATO chrome moly (not chrome lined) with the midlength gas system I prefer. It has standard (tight fitting) hand guards, a fix front sight tower and an optics-ready flattop receiver.

It came with a very generous accessory package: Sabre logoed soft tactical case with 4 mag pouches (finally a free case that is useful!), two 30rd Sabre stamped Teflon coated aluminum mags (that work great), Sabre logoed Otis cleaning kit, sling, lock, and unfired sighting-in target.  This is the package included with the expensive Sabre models.

Customizing it is more like wood shop than gunshop.  I thought I would be locked-in with the design, but other owners have been able to do some interesting and useful mods to the polymer stock.  It would be a perfect plinking, self-defense, truck/trunk gun.  Owners who jump out of helicopters and troop transports and need a collasping stock (I rarely use that feature) or need swap out each and every piece once the buy an AR (been there, done that) won't like it.

But I like it alot, even past the honeymoon phase.  It has many features I like and few negatives.  It injected variety into my AR collection.

Close up of a CAV-15 MkIII (under development)
Note: SHE is not under-developed

Nice rifle!

Your post reads like a paid actor infomercial.

I built a like rifle myself using a CAV ARMS lower and Delton upper. Very well balanced.

Hootbro

Yeah, I'd say she is completely developed.

Yours looks really good with that detachable A2 handle.  I just put on an MI backup rear sight and was good to go.

It's a CNC A1 handle.

Here are more details about the SDI US Military contract:

"Sabre Defence Industries, LLC, a government contractor for the manufacture of machine gun parts and accessories and commercial XR15 rifles, has been awarded an IDIQ contract for a minimum of 4,952 M16A3 and 702 M16A4 rifles to support the U.S. Navy, U.S. Marine Corps, and foreign military customers.
Nine bids were received. Sabre becomes only the third company in the 45-year M16 history, besides Colt and FN, to be awarded a contract to supply a Mil-Spec M16 to the U.S. government.
The M16 project will take place at Sabre Defence's Nashville, Tennessee facility and is expected to be completed by end of December, 2010."

Whoever you quoted needs to check their facts. Bushmaster had a small lot M4 contract before SABRE. Also left off H&R and GM making Vietnam era M16's.

I like mine (Cav15w/SDI Upper) more then my issue M4 thats for sure. The lighter weight is very nice, and I like the mid-length handguard setup better. All in all its a great handling weapon.

Sabre defense is good to go. They make good stuff.

I'd like to see the m16s in the hands of Americans..pics please!

In order to inform those new to the polymer lower design, I wrote this 26 item list of unique features about my SDI XR-15A3LW (on another forum). Some of it may only apply to my brand (SDI) and not the CAV-15 (Cav Arms supplies the lpolymer lower to SDI). Any gunsmithing I mention may not be officially sanctioned by either SDI or Cav Arms.

"I would like to touch on a few idiosyncrasies about the polymer lower, especially for potential owners and those not familiar with the design. There are many parts that are eliminated with the unitized design, a few different parts, and a scant few new parts. The designers did their best to share parts as much as possible with standard AR-15's, and they did a very good job of it.

1. Despite the A1 rifle length stock, a carbine buffer and carbine buffer spring are employed. So don't try to fit a rifle length buffer and spring in this gun. This carbine buffer system allows some "chopping" of the stock.  The A1 length is intentional and not a backwards step from the longer A2, because many shooters prefer the A1 length which gives a length of pull of 13", very good for all around use.
2. There is no metal buffer tube/receiver extension as this is integral with the stock.
3. Because of the design, the buffer retaining pin cannot be held captive by a screwed-in buffer tube. Instead, there is a transverse roll pin that is drifted across the base of the retaining pin. This is one of the few unique additional parts, but it is a generic size that can be found from many sources.
4. The castle nut, spacer, buffer tube, takedown pin detent/detent spring, pivot pin detent/detent spring, and separate rear stock are all eliminated. No more friggin' castle nuts!
5. The polymer lower has extra outer wall thickness in several key areas: the upper/lower interface, the take down and pivot pin areas, mag well, hammer pin area, and stock/grip/lower junction.
6. Because of the extra thickness at the takedown and pivot pin holes, longer pins are required. These are of normal diameter and will fit standard AR-15 uppers. However, they are a unique longer part which can be purchased from Cav Arms (and possible SDI?) for a nominal $5.
7. Neither the take down pin nor pivot pin are held captive in the receiver. That means they could drop to the ground, roll, and get lost, so don't disassemble in an uncontrolled, debris-strewn area. You soon learn how to catch these pins when taking down.
8. The pins go in "the wrong way" left to right compared to a regular AR where the pins go in right to left. It has been known for the pins to be placed in the opposite way and to have the pins come loose. When placed correclty they are well-secured by tight friction and ball detents built into the pins.
9. The upper/lower fit is tight and the takedown pin can be very tight, requiring a rubber mallet or non-marring push tool. Don't use tools that might mar or abrade the lower or pin holes. Once the takedown pin is out, the pivot pin comes out without tools.
10. Some users have corrected an overly tight takedown pin by lowering the upper and seeing how the holes line up. The polymer takedown holes can then be GENTLY relieved with a round file, in small steps, checking fit often. A novice should not attempt this as it can be irreversible. You would really have to over ream it to get a loose fit. I did it enough so that I can disassemble with a moderate tap and can reassemble without a tool. I stopped well before going too far.
11. The pistol grip, grip screw/washer, trigger guard, and trigger guard parts/pins are all eliminated.
12. There is a safety detent and spring, but they are inserted before the safety from above, not below. To remove the safety, you cannot remove the grip to relieve the detent spring, the safety must be wiggled and drifted out under detent spring pressure. Some users have added a slight bevel to the safety to facilitate safety removal, but mine can be removed as needed.
13. The polymer material adds some friction compared to aluminum alloy. Two critical areas are the bolt catch area and the mag well.
14. The Cav Arms recommendation is to clip 1 to 1-1/2 coils from the bolt catch spring if old mags do not lock the bolt back. My bolt catch area needed slight tuning on my part which I will describe in a later more detailed post.
15. If a magazine drags or does not drop free from the mag well, the first thing to do is try another brand of magazine. 30rd NHMTG aluminum mags and polymer PMags fit my rifle great. 20rd NHMTG aluminum mags have tiny rivets on the front strap, that can drag the front inside of the mag well.
16. To correct this problem, the upper and lower are seperated and an empty mag is inserted. Looking from the top, the contact area can be observed and filed down. Again slowly and gradually with frequent refitting. You can take off too much and end up with loose mags.
17. If things get botched, Cav Arms will replace an abused CAV-15 lower for a nominal $30 fee. I don't expect SDI to do this, So I was careful not to go to far.
18. To repair a non-cracked holed spot or area were too much material was removed, some owners have used a liquid metal epoxy mix to patch. This might work inside the mag well for example where it would not be too unsightly. My advice is not to get to this point.
19. A slot is cut in the rear stock for a sling. Cav Arms can also custom cut a forward slot for one point slings. Some owners have drilled an inserted quick detach sling mounts (plastic welded in place) with very good results.
20. I did not care for the creepy trigger pull, so I upgraded the trigger group with an extra set I had on hand. I can give more details later.
21. The integral pistol grip has no finger projection. This allows a Hogue handall slip-on grip to be fitted. This gives a rubbery non-slip grip with adjustable finger grooves and palm swells. The bare grip is nice and well-shaped, but the Hogue makes it even nicer.
22. The back of the grip is shaped more like an ergo grip, so for those with short thumbs, the reach to the safety can be long. The new CAV-15 Mk III is being developed and decreases reach to the safety. This is probably not a user mod as there may not be enough thickness to remove enough material on a MkII.
23. I filed a finger relief under the trigger guard and got a nice result. Again, don't do this if you are afraid of holing the stock, as it is hollow.
24. If you reshape the stock, the matte texture of the surface will be lost, so be advised. A sanded area can end up being light colored, but a little rubbed on gun oil will darken it up.
25. Because of the extra thickness of the lower receiver at the hammer pin area, an installed standard hammer pin will be recessed in the receiver on both sides. This has been known to be a concern for new owners. However, there is nothing to be alarmed about as this is normal and a longer hammer pin is not required. Just make sure the hammer pin is captured but the hammer J wire. When drifting the hammer pin, a non-marring and correctly sized drift tool should be used. A spare hammer pin can be used to start or seat the pin. The extra receiver thickness is a good thing as this is a high stress area.
26. The outside of the magazine well being thicker allows for a special slots on the inside. Regular AR-15 magazines work of course, but you can also insert .45 cal (double stack) grease gun magazines or 9mm magazine blocks for pistol caliber conversions. Lots of people shoot 9mm AR conversions. With this lower, you could be shooting 45 ACP."