So I've recently come into some cash and am looking to upgrade my current AR-15 (DPMS panther lite) to something a little more...substantial. To be honest, I haven't really had any issues whatsoever with my DPMS, but then I've only had about 500 rounds through it. The only thing I'm not crazy about is that for some reason or another it has much more "felt" recoil than some of my friends' AR's that I've shot.

Anyway, I've done quite a bit of research on the gas-piston vs. traditional AR's, and I'm still not convinced either way. Just when 87GN convinced me that the Colt 6940 was the way to go (he poo-poo'd the idea of a gas-piston rifle I was considering and provided some interesting evidence to back up his claim), I talked to a certified Colt (and Glock) armorer who has been in law enforcement for 25 years, and he suggested that, out of the two I was considering, I should go with the Sig 556. Consider this:

In a traditional AR-15, most of the face-melting hot carbon-filled gasses are shot straight back in the chamber. In a gas-piston system, most of the face-melting hot carbon-filled gasses are confined to a tube. Therefore theoretically, it would follow that gas-piston systems will remain cleaner for longer. I find this to be a compelling argument. However, many (like 87GN whom I respect immensely) argue that it just doesn't matter, i.e., that real-world data have proven that getting all the carbon-laden gasses in the chamber of a traditional AR doesn't affect its ability to operate enough to warrant getting a gas-piston type AR. I also find this to be a compelling argument, because many gas-piston rifles are heavier (like the Sig) and aren't "standardized" like regular AR's.

I have to say at this point that I am literally 50/50. The Sig is about in the same price range as the Colt. Besides the gas-piston system in the Sig, is it more accurate than the Colt? I know I'm being anal about this, but when I'm about to drop 1500$ on a rifle...I think I have a right to be anal!

What says the horde? Sig or Colt, or maybe something else completely?

Personally, I am not too interested in the piston ARs. I have looked a lot at the SIGs, and even with the rebate, felt I could get a better AR rifle for the same money, and have something with a ton more parts, accessories, and compatibility. For waht you are looking to spend, you can get an awesome top tier AR. Not just the Colt either, you can do some real stuff from BCM, Noveske, LMT, and others. Take your time, look around. That's what I did, and my Noveske is being shipped as we speak.

I am in the military and a civilian contractor, Ive been to a few shooting schools and shot alot of rounds...several times 1500 rounds in a day for 3 days straight. Gas Piston and DI are both good designs, Gas piston is cleaner, until you suppress it. All of my rifles are DI and I have not had 1 problem with them....ever.
I'd go with a proven DI system...Colt for instance. I also find a mid length gas system works very well...it may be something worth looking into.
Besides Colt there are quite a few other top teir AR manufacturers out there so dont limit yourself to only Colt because there are better out there than Colt.

556's uh well besides being really ugly, they are good guns, I've shot them quite a bit but I'd rather stick to a combat proven standard AR platform.

oh and I own a Noveske.....but Daniel Defense, BCM, LMT, and KAC are my other favorites aswell.

If it has to be one of the OP's 2 choices  , then I say Colt 6940 .

If your still considering your options , then consider the Colt 6920 instead of the 6940 .

Why ?

2 reasons .

1.The 6940 comes with a unique rail and D-ring IIRC .If either breaks only Colt makes replacement parts,or
you have to tare down the rifle to completely change the original ring and go to a standard set up .

2.I prefer to have a solid A-frame front sight and a folding rear BUIS .
If the optic is incapacitated ,all you have to do is fold up the rear .
Also with folding front and rear BUIS your adding  variance and the potential for mechanical failure in your sights at both ends .

The second is purely opinion BTW . I just prefer to leave the front sight permanently fixed  but the
rear out of my way .

With the money saved between the Colt 6940 and 6920 you can buy a rail yourself .

I like this option.  Get a 6920 and pick the rail you want.  

The 556 is a cool gun and I like it alot.  However, I havent bought one because i already have an AR that does everything it would do and I got to build it myself.  The parts and accessory compatibility of the AR is hard to beat.

Colt

I have to ask though, to what do you attribute the recommendation of the Sig from the Glock/Colt armorer? I've known this guy since I took a firearms course from him. He is one of the senior officers at my University's police department, and he has worked for many other city departments as well. He's also one of the range-masters for the University PD's range, which students are allowed to use if they have taken the University's course. I've been into guns for a while and I know this guy is legit, so his opinion has to count for something right?

You go into an AR15 forum, so you should have known what people were going to say.

Why the hell did they go with SIGs?

Very constructive, thanks! People like yourself are the reason Arfcom has such a golden reputation!



And MSTN, I'm not quite sure what that link goes to (?)...regardless, while that story is intruiguing, is there any documentation of it?

I got a Colt M4 and a Sig 556 on T&E. Both shot well.

The Sig was bulkier and a bit heavier.
Out of the box some little plastic piece fell off pertaining to the folding stock. The rifle seems a bit junkier than a proven AR15 design. I just do not think it will hold up over the long haul.
Many of our officers are prior military. They know the AR15 platform, that a big plus for training and maintenance.
The Sig 556 is more related to an AK than an AR.

There is a very good reason why they are offering a rebate and I would suspect they will eventually discontinue or major redesign it.

i own 8 Colts and my 6940 will be here Monday and my 6933...who knows?? but i also owned a SIG 556 with alot of upgraded options. ill just leave it at this..i own 8 Colts right this moment and 0 Sig rifles. They are not bad, just heavy and  not up to par with top tier AR's.

I've owned both for what its worth.  I still own a 6920 (m4).

Sigs are cool but the are $$$$$$$$$ even for upgrades.  

Now if I could afford a 552 I would.

Bullshit

I'm just telling the truth. You won't get a good opinion because the thread is clouded by bias.

My vote is an AR15 over the SIG. No dissing on the SIG, but an AR15 is like owning an 870 or 1911. As you can see at this site, the market and aftermarket is huge.

I have both piston and DI uppers and like them both. In shortys and full auto, the cleanliness of pistons work for me. Do a beta mag dump with the LMT 10.5" and its very hot, same from the POF 11.5 and it's only hot. I believe in the accuracy benefits of DI for precision shooting (no piston system moving about as the bullet travels down the barrel).

If you want a piston, there are a ton of options out there; and that is a problem - there is not a standard system like DI, they are all pretty unique.

OP; Next time you're at a gun show, first pick up a Sig by the pistol grip, then pick up a Colt or other M4-type. If you don't believe what you're experiencing, go back and shoulder both rifles. Yes, the Sig is noticeably heavier in the front and generally feels more like a .308 battle rifle. I was extremely interested in one until I did this. Plus, they look like junk. I'm fully aware of the benefits of a piston gun, but seriously, do you know anyone whose face has been 'melted' by the exhaust gas of an AR?
The only serious alternative to me is the Para TTR. With this you get the semi-piston system plus folding stock.

Could you not type in caps?

IIRC it is an issue with his Point of Sale Program on his work computer that it only recognizes caps.

I do know of another department that bought 556's, I will see if I can get one of them to pop in here with an opinion on them.  

I am happy that we don't have SiG556 here, but nly 550, 551-552 and maybe the best of all, the 553....

the only thing i'd like from the 556, is the ability to use USGI magasines into my 550, or 553...

oh, btw.. I am not biased.. besides my SiGs, I own 6 AR-15, 2 Ak47 etc....

A Sig 556 is a great rifle if you own a Ar15. But if you want to spend your money wisely. Get a good Ar15. Bye Colt, LMT or Noveske. The DPMS light weight is a nice rifle. You might also just want to up grade it with a new upper. Mid leingth or Stock assy. But for some reason SIG which had a steller rep. Has been bulding and selling less than the best stuff out there. I am not sure if its just Sig USA or the co. as a whole has problems? Still love my Sig pistols. My P-220 is my go to gun.

there are no changes in quality for the SiG's that are sold out here.. i guess it's a SiG USA specificity.

Which rifle will be more accurate (assuming they're shooting identical rounds under identical conditions)?

Btw thanks for all the info, this is very useful.

I have owned 3 Sig 556s.....and use to hang out on their forums....

I sold them and am now hanging around here.....

Colt 6940 LE
LMT Defender 2000
Stag 15
Bushmaster

Ok I read somewhere that the 556 did not have a chrome-lined barrel...is this true??

I dont understand why SiG made such a product hurting it's reputation..

they just had to produce a SiG553...

I'm sure because they had to manufacture it in the States that they went into the ever popular 'cost saving' mode, relying more on it's name association with the original 55x. Not to say it's not a capable rifle - I just think that since the original 55xs were banned from importation, so few are in circulation, and having no direct civilian counterpart, the 'halo' status of these products work against the 556, especially when the differences are highlighted.

The Sig 556 is garbage.  And yes, I have experience with them.

Get the Colt, if those are your only options.

Colt 6940!!

Sorry now I actually read the thread. Sig vs Ar15 platform??? Get a life.

Thanks for contributing to the TECH-FORUM discussion.



 

If I could only choose between the SIG & the Colt, I'd go with the Colt.



And as it's been mentioned, there are several good alternatives to Colt too (BCM, Noveske, DD, ect).



But you could also just buy a better upper for your existing rifle & put a better FCG in the lower while you're at it.

Guys...I'm the other guy that carries the Sig556 for duty.  Although not a perfect duty rifle I know that it will run any ammo through any magazine that there is.  The Sig556 had gotten a bad rep for several reasons but the biggest was that it was something different than the current AR15.  This reminds me of the debates between the m16 and m14, m14 and m1garand, a bolt action and a semi-auto.  There are many difference between the Sig556 and the Ar15 and many things that are the same.  However just reminded yourself that se currently can get both of these rifles, be happy you have the option s.  As for myself I would be happy with either rifle for duty but currently I'm carrying the short barrel select fire Sig.  Not bad for a simple patrol officer.

It's not even close in my opinion. I would much rather have the Colt. If there is something wrong with the DI system I guess someone should tell Pat Roger's BCM, which currently has more than 29,000 rounds downrange without being cleaned, only well-lubed. However it sounds like you don't want to hear the truth so just get what you seem to want (Sig 556). It's your money in the end so spend it the way you want or you won't be happy.

I don't have shooting experience with the Sig 556 save holding one. I do have with the Colt 6920 and 6721 very good rifles. As far as accuracy for those Colts, with good ammo 1MOA is not a problem. I don't think you could go wrong at all with the Colt. Your budget will allow you to purchase a rail too .

I am interested in the gas piston systems, curious enough to have one (LWRC) on the way this week.

Well, it looks like I'm going with the Colt 6940. I would have liked a Noveske, but it was a little out of my price range. Thanks for all the input!

And btw, I'm puzzled about why my thread got moved. The logic escapes me; a Colt 6940 is an AR as much as a Sig 556 is a gas-system rifle, so couldn't this thread exist in either forum? In other words, it could  just as easlily be moved out of this forum by virtue of the fact that the thread mentions a DI AR-15 since it was (apparently) moved out of the AR-15 forum by virtue of the fact that the thread also mentions a gas-piston rifle. I would rather it had stayed in the other forum since very few people post in this one.

Or is it a sin to question the almighty moderators ?

Colt, Sig556 is really a project waiting to be completed.  Maybe in a couple years Sig will get serious and release it right...

I would wait until the H&K MR556 comes available... i own  the MR223 (european/canadian version) and it is the best of all my AR's (and ive owned more that a few)..... stay away from the Sig556 or the 516 for that matter..

the MR556 should be out by summer 2010

and for all the guys who keep suggesting the Colt i suggest you go to YOUTUBE and type in H&K 416 vs Colt..it will change your view..

They Nitride treat the hammer-forged barrels. IIRC, none of the original Sig 550/551/552/STG90 ever had chrome-lined barrels, so it is not out of the ordinary for the 556 to not have it.

Oh no you didn't just bring that up?!

Stoner worked hard and brilliantly to develop the AR. It has no piston intentionally I assume. It is simple and has worked remarkably well for years.
A piston modified AR works, and even some work well, but they are more complex... by default and then you get into bolt carrier canter etc.  I am not certain the AR was ever designed for a piston system, perhaps a hybrid version and not called AR is a viable answer.
This said, I want to build one around the Osprey gas system and try it.