Colt 6940P--Piston Parts Pics

[Tokarev]

We haven't seen much posted about this different and unique rifle. Yes, it's a piston but I say it's different and unique because Colt's approach to the parts is quite unusual. Rather than use a solid rod, Colt added a swivel joint. This joint allows the piston to "float" free of the rod. This, in theory at least, keeps the piston from adding any undue stress on the barrel when things start heating up.

Here's the assembled rifle. Note that Colt used a built-in folding front sight rather than a railed gas block. Excess gas is vented out the small bleed-off hole located on both sides of the block.
http://img.photobucket.com/albums/v221/tokarev/P1020010_zpse40fe559.jpg

To access the piston, the small captured pin is pushed out as far as it will go. This allows the piston parts to be removed as a complete unit. Note the opposing grooves in the block. These help free the piston if it's frozen in place from carbon. Twisting the plug will cam it against these surfaces and help with removal.
http://img.photobucket.com/albums/v221/tokarev/P1020007_zpse2430066.jpg


The piston assembly removed from the rifle.
http://img.photobucket.com/albums/v221/tokarev/P1010986_zps690bcb09.jpg

The piston parts disassembled.
http://img.photobucket.com/albums/v221/tokarev/P1010987_zpsab78bd58.jpg

The transfer rod is attached to the piston by means of a small internal snap ring. The two parts are easily seperated by simply pulling them apart.
http://img.photobucket.com/albums/v221/tokarev/P1010989_zps51515f87.jpg

The piston. Note the three small gas rings.
http://img.photobucket.com/albums/v221/tokarev/P1010990_zps8497dbc2.jpg

The ball on the end of the transfer rod that works as the joint for the piston.
http://img.photobucket.com/albums/v221/tokarev/P1010992_zps5f5ae048.jpg

This is the latest style from Colt with the solid bolt carrier.

[Airhasz]

Thanks for sharing pics, first look for a lot uf us.

[amd5007]

Thanks for doing this. I've wondered about details of the Colt Piston carbine. I've heard that the carrier and upper receivers are different as well. Perhaps you could post some more pics of the details farther back.

[eternal24k]

This is the first time the 6940P peaked my interest,
thanks for sharing.
Looking forward to some range reports

[Tokarev]

Thanks for doing this. I've wondered about details of the Colt Piston carbine. I've heard that the carrier and upper receivers are different as well. Perhaps you could post some more pics of the details farther back.


I'll see what I can do tomorrow. I'm hoping to shoot the rifle in the morning but it might not happen until Tuesday.

[El Pistolero]

Hmm, I suddenly want a 6940P with a 14.5-inch barrel. I wonder how accuracy of the 6940P compares to the 6940, with the both being free-floated and just about identical other than the piston parts.

[Tokarev]

Surprisingly, the gas plug only has one gas port and there is no provision for suppressed settings. I can only assume the gas vents in the block allow any overpressure to exit before adding excess gas to the system.

I can't seem to find anyone with an AAC 51T flash hider in stock so I can't run my suppressor on the Colt for the time being. If I can't find a 51T in a couple weeks, I'll pull one off one of my other rifles so I can see how the Colt works with a can attached.

http://img.photobucket.com/albums/v221/tokarev/P1010999_zps3124723d.jpg
http://img.photobucket.com/albums/v221/tokarev/40e5f6ca-ea8c-4941-84ca-70747ca8d9c8_zpsb4068985.jpg

[tog]

Reminds me of the FAL gas system. Add a gas adjustment nut and you will have a Colt FAL.
Tog

[El Pistolero]

Reminds me of the FAL gas system. Add a gas adjustment nut and you will have a Colt FAL.
Alien

Don't tease me. The FAL is one of my favorite rifles of all time and I'm a Colt fanboy. The two together, well that would be just epic but impossible.

[tog]

Don't tease me. The FAL is one of my favorite rifles of all time and I'm a Colt fanboy. The two together, well that would be just epic but impossible.

I agree. Big, big FAL fan here, though I am learning to love the m4.

[mastiffhound]

If you could get a few pics of the BCG it would be much appreciated. Thank you for the look at the piston, I was wondering what they came up with.

[Tokarev]

If you could get a few pics of the BCG it would be much appreciated. Thank you for the look at the piston, I was wondering what they came up with.

I should be able to get some photos of the inside of the upper and the BCG tomorrow.

I didn't think anyone would want to see these since pics of the upper and BCG have already been posted elsewhere. Sorry for the oversight.

[sinlessorrow]

Don't tease me. The FAL is one of my favorite rifles of all time and I'm a Colt fanboy. The two together, well that would be just epic but impossible.

:big_boss: FO SHO.

Looks like Colt came up with a great innovative piston system. I usually am not a big piston fan, but I am a Colt fan and I will pick one of these up when they come back. Still curious to see how it performs for the Army.

[MistWolf]

It increases the number of smaller, easier to lose, fragile parts. I'm not sure that's a good thing

[Magic_Salad0892]

I wondered what "articulating link" piston meant.

I kind of like this design. Not sure if it's better than HKs, but it's nice. It does remind me of a FAL kind of.

I'm dissapointed that there isn't an adjustable block on it. Or adjust gas/front sight like the LWRC M6A3.

But the Colt front sight isn't bad.

Overall it doesn't look awful.

I've been anti-piston the past two years or so. But I think this gun looks sweet. And I'd love to shoot the SCW 10'' version.

[sinlessorrow]

It increases the number of smaller, easier to lose, fragile parts. I'm not sure that's a good thing

It hasn't been an issue through history.

[sinlessorrow]

I wondered what "articulating link" piston meant.

I kind of like this design. Not sure if it's better than HKs, but it's nice. It does remind me of a FAL kind of.

I'm dissapointed that there isn't an adjustable block on it. Or adjust gas/front sight like the LWRC M6A3.

But the Colt front sight isn't bad.

Overall it doesn't look awful.

I've been anti-piston the past two years or so. But I think this gun looks sweet. And I'd love to shoot the SCW 10'' version.

The one submitted to the IC has an adjustable block for suppressed shooting. I bet if they get it we will eventually see one.

[twistedcomrade]

Interesting for sure . What is the MSRP on these rifles?

[sinlessorrow]

Interesting for sure . What is the MSRP on these rifles?


You could get them for $1,700 back before the craze. I believe I saw some on GB for below $2,000 but most are $2,500.

[thehun]

Now thats a piston kit I would have

[BH321]

You could get them for $1,700 back before the craze. I believe I saw some on GB for below $2,000 but most are $2,500.

Here is one Grant is selling on Gunbroker (http://www.gunbroker.com/Auction/ViewItem.aspx?Item=330798371). And before anyone goes all "Grr price gouger, evil!", Grant doesn't have real time inventory on the site so if he put it up on his site he would get overwhelmed with responses and have to cancel all the excess orders. He only had the one come in and didn't have any backorders for them so he threw it up on Gunbroker. If you want to get on the backorder list for an item send Grant an email.

[KiraX105]

I currently have one of these neat rifles. Well, its not here, its at Colt for repair.

The piston rod broke during a firing string creating a single shot wonder. the rod snapped about 1 inch in from the receiver. As only the bottom rail is removable I had to send it back to Colt for repair. Colt customer service has been so so thus far. The rifle was received at Colt on 5 Oct 12 and Lewis, the Cust Service rep, has always been polite and accomidating in the status of the repair.

I found the accuracy of the rifle to be no different than that of my personal 6920, 6721 or my issue M4

[sinlessorrow]

I currently have one of these neat rifles. Well, its not here, its at Colt for repair.

The piston rod broke during a firing string creating a single shot wonder. the rod snapped about 1 inch in from the receiver. As only the bottom rail is removable I had to send it back to Colt for repair. Colt customer service has been so so thus far. The rifle was received at Colt on 5 Oct 12 and Lewis, the Cust Service rep, has always been polite and accomidating in the status of the repair.

I found the accuracy of the rifle to be no different than that of my personal 6920, 6721 or my issue M4

What revision was it? The newly modded ones or the older ones.

[MistWolf]

It hasn't been an issue through history.

Quite the opposite, actually. One of the things designers do to GI proof weapons is to eliminate as as many small, easily lost parts as possible. When a weapon does have such small parts, they are usually not part of the field stripping process. That's one reason the FCG of the AR isn't supposed to be removed by the GI in the field.

Do a search on most of the discussions of op-rod piston systems on this forum. One criticism that is continuously is that there are more parts critical to function that can get buggered or lost. One area Colt missed the mark is that the piston & op-rod are made up of multiple pieces. The piston & op-rod of the FAL is one piece plus a spring and no gas rings.

I cannot tell for certain from the pictures but it looks like Colt may have made the op-rod adjustable for length. Why?

Some have mentioned they'd like this system to have a manually adjustable gas regulator. That is a step backwards. Self regulating gas systems have proven to reliably handle a wide variety of ammo under a variety of conditions and do so with fewer moving parts. There are those on this site that state the A2 adjustable sights are undesirable because they can get played with and throw the zero off. Other than the ability to switch from suppressed to unsuppressed use, why is an adjustment that can stop the rifle from functioning desirable?

Finally, what makes the Colt op-rod system better than other AR op-rod systems? What does it bring to the AR family of weapons that the original carrier piston system does not? What is the pay off for having an AR with proprietary parts that adds to the complexity of the gas system?

[sinlessorrow]

Quite the opposite, actually. One of the things designers do to GI proof weapons is to eliminate as as many small, easily lost parts as possible. When a weapon does have such small parts, they are usually not part of the field stripping process. That's one reason the FCG of the AR isn't supposed to be removed by the GI in the field.

Do a search on most of the discussions of op-rod piston systems on this forum. One criticism that is continuously is that there are more parts critical to function that can get buggered or lost. One area Colt missed the mark is that the piston & op-rod are made up of multiple pieces. The piston & op-rod of the FAL is one piece plus a spring and no gas rings.

I cannot tell for certain from the pictures but it looks like Colt may have made the op-rod adjustable for length. Why?

Some have mentioned they'd like this system to have a manually adjustable gas regulator. That is a step backwards. Self regulating gas systems have proven to reliably handle a wide variety of ammo under a variety of conditions and do so with fewer moving parts. There are those on this site that state the A2 adjustable sights are undesirable because they can get played with and throw the zero off. Other than the ability to switch from suppressed to unsuppressed use, why is an adjustment that can stop the rifle from functioning desirable?

Finally, what makes the Colt op-rod system better than other AR op-rod systems? What does it bring to the AR family of weapons that the original carrier piston system does not? What is the pay off for having an AR with proprietary parts that adds to the complexity of the gas system?

The original LE1020 used a one piece fal type op rod, they moved to this for IC, I'm sure there is a reason.

Soldiers also seem apt enough to maintain the many small parts of the m4, including the FPRP, the Extractor pin, the extractor, the cam pin, I don't see what difference a few parts 4 times+ the size of the cotter pin would make.

[Arctic1]

Quite the opposite, actually. One of the things designers do to GI proof weapons is to eliminate as as many small, easily lost parts as possible. When a weapon does have such small parts, they are usually not part of the field stripping process. That's one reason the FCG of the AR isn't supposed to be removed by the GI in the field.

Do a search on most of the discussions of op-rod piston systems on this forum. One criticism that is continuously is that there are more parts critical to function that can get buggered or lost. One area Colt missed the mark is that the piston & op-rod are made up of multiple pieces. The piston & op-rod of the FAL is one piece plus a spring and no gas rings.

I cannot tell for certain from the pictures but it looks like Colt may have made the op-rod adjustable for length. Why?

Some have mentioned they'd like this system to have a manually adjustable gas regulator. That is a step backwards. Self regulating gas systems have proven to reliably handle a wide variety of ammo under a variety of conditions and do so with fewer moving parts. There are those on this site that state the A2 adjustable sights are undesirable because they can get played with and throw the zero off. Other than the ability to switch from suppressed to unsuppressed use, why is an adjustment that can stop the rifle from functioning desirable?

Finally, what makes the Colt op-rod system better than other AR op-rod systems? What does it bring to the AR family of weapons that the original carrier piston system does not? What is the pay off for having an AR with proprietary parts that adds to the complexity of the gas system?

1. Your point about GI proofing is not really valid, as you probably have not been around many machineguns, and you are also wrong about it being an issue in my opinion.

Take the FN-MAG for example, where you have loads of small parts that must be removed in order to clean it properly; gas system/gas regulator, top cover, bolt etc. Loads of parts than can possibly be lost during disassembly. Same with the MG3, the bolt carrier group consists of 12 parts alone(15 if you dissassemble the bolt/extractor).

When you compare some of these parts to the FCG of an AR, they are much smaller. And what about the cotter pin on the BCG?

While there are some assembly difficulties during the early part of training, they go away with repetition.

2. I agree that their choice of a 3 part system is odd, but the reason might be ease of parts replacement, if wear is focused on one part. I do not agree with your statement about a piston system equalling more parts that are prone to failure or being lost. The wear on the piston and op-rod on the HK416 is negligible. The wear prone parts of the operating system are the gas rings, same as on the M4 bolt.

3. Adjustable gas regulators are a very nice feature to have, in my opinion. If the system is easy to use, intuituve as well as secure, then I have no issue with it. It can not compromise reliability.

4. What is the point in trying to be innovative, trying new designs, trying to improve their products? Clearly we should never change anything, because what we have works so well and has for so long. Right?

I see this attitude among many senior O's who often do not see the point in changing out some of the gear we have, they often oppose such efforts strongly. One example was the acquisition of electronic, comms compatible hearing protection (specifically Peltor ComTac XPs). One of the O's involved in the project, a Colonel, stated that he really didn't see the point; he had used ear plugs and normal muffs during his career without issue. It should still do the job. Fortunatly reason was victorious, and we are starting to be issued these service-wide. In addition, every soldier is issued active hearing protection (Peltor SWAT Tac).

I agree that change for the sake of change is pointless, but we should not criticize or be negative towards new designs or changes because we want to hold on to what we like.

[Tokarev]

Here are some additional pictures. If there's anything else that anyone would like to see, please let me know. I'll do my best to get the photograph(s) for you.

Here's the left side of the receiver showing the steel cam pin insert. It has been reported that this small steel plate was added to eliminate the wear that's usually present in piston guns from "cam pin drag." Colt is the only manufacturer I'm aware of that is adding a special plate to deal with this. Other makers--SIG for example--is removing the material that would normally be rubbed by the cam pin. It will be interesting to see which approach ultimately proves to be the better one.
http://img.photobucket.com/albums/v221/tokarev/P1020011_zpsb134f60f.jpg

The steel plate as seen from the inside.
http://img.photobucket.com/albums/v221/tokarev/P1020017_zpsbf643435.jpg

http://img.photobucket.com/albums/v221/tokarev/P1020015_zps89086bfb.jpg

The piston rod as it sits inside the upper.
http://img.photobucket.com/albums/v221/tokarev/P1020014_zpsc0d1f165.jpg

The newer one piece bolt carrier. There is no chrome lining to the interior of the carrier.
http://img.photobucket.com/albums/v221/tokarev/P1020018_zps968d22f9.jpg

The tail end of the bolt carrier has the raised ribs or skis as used by most makers nowadays.
http://img.photobucket.com/albums/v221/tokarev/P1020019_zps67531996.jpg

Standard GI bolt.
http://img.photobucket.com/albums/v221/tokarev/P1020020_zpse3561178.jpg

Here's the extractor. Black insert and gold spring.
http://img.photobucket.com/albums/v221/tokarev/P1020021_zpsfcdd8ee1.jpg

Chromed chamber and bore.
http://img.photobucket.com/albums/v221/tokarev/P1020022_zps70e7228d.jpg

[sinlessorrow]

Have you taken it out for a test run yet? It looks nice.

[MistWolf]

1. Your point about GI proofing is not really valid, as you probably have not been around many machineguns, and you are also wrong about it being an issue in my opinion.

Of course, the more complex the machine, the more complex the parts. A machinegun has more small parts than an infantry rifle and an aircraft has more small parts than a machinegun. I agree training is an excellent answer. My point is, other op-rod conversions get raked over the coals for adding complexity to the AR. This one has even more parts than other AR op-rod systems that I've seen, yet that's ok.


2. ...I do not agree with your statement about a piston system equaling more parts that are prone to failure or being lost.

I make no claims about wear or early failure on this one. I can tell you from long experience, small parts constantly get mis-placed & lost and the more parts there are, the more likely they get lost. That's why as a technician, it's very important that I keep the work area and the parts neat, organized and tagged. A soldier in the field does not always have that luxury


3. Adjustable gas regulators are a very nice feature to have, in my opinion. If the system is easy to use, intuituve as well as secure, then I have no issue with it. It can not compromise reliability.

I cannot tell you how many times I've read a post about a FAL that won't function only to find out it's due to the gas regulator being out of adjustment, most times because someone had finger fiddled it. I find it interesting that it's not ok to have sights a soldier will fiddle with throw and change zero but it's ok to have a regulator to fiddle with that can turn the rifle off


4. What is the point in trying to be innovative, trying new designs, trying to improve their products? Clearly we should never change anything, because what we have works so well and has for so long. Right?

I like changes that make my gadgets operate better, easier to maintain or improve safety. This innovation doesn't do any of those. As a technician, I see potential problem areas on this new piston/op-rod that I would be keeping a close eye on until they've proven themselves


we should not criticize or be negative towards new designs or changes because we want to hold on to what we like.

I'm not critical because I simply want to hold on to what I like. I'm critical because historically op-rod systems in ARs bring no practical improvement over the original. What does this do that the traditional AR gas system does not? What advantage does making the op-rod in several pieces have over a single piece? Nearly every good improvement makes a machine simpler, especially when talking about mature technology. The Colt op-rod system is NOT simpler

[tog]

Good looking rifle!

[skydivr]

I've got one too. Just as accurate as the DI rifle. Bolt and BCG stays REALLY clean. Gets pretty dirty inside that gas plug, but don't know if that effects performance or not.

I just wanted to try something different. While it's a nice rifle, I think if I could only afford one, I'd stick with DI and the regular 6940; less parts to go wrong/commonality with milspec DI parts.

I hope my doesn't break the operating rod. Would like to hear how it works out suppressed...

[thehun]

I really dig this Colt...i think if I was going to switch..it be to a SCAR

[BoringGuy45]

I like this! I have a feeling that the IC is going to come to nothing and the Army is going to decide it's just fine with the current crop of M4s and M16s. If the IC does produce the next service rifle for the Army, I hope it's this one. From what I've seen, it sounds like it's the closest to the current DI guns in terms of weight and balance.

However, if the IC does indeed produce a service rifle, I'd imagine it would be the 416.

[DreadPirateMoyer]

Unbelievable. The same people who scream in every other thread that piston systems shouldn't be utilized in the AR-15, that it wasn't designed to take operating systems outside of the Stoner architecture, and/or that piston guns offer up nothing over DI guns...

...are now saying they'll buy one of these and are excited to have it? All based on some pictures? Glad we're consistent in our opinions and objectively evaluate what's presented to us. I'm sure everyone oggling over this would still love it if "Colt" weren't in front of the model designation, right? :rolleyes:

On that note, I'd be anxious to see a torture test of this gun. I don't like how many parts go into the op-rod assembly, nor that pins are required for system take down. On its face, it doesn't seem to offer anything over the piston systems currently available on the market, especially at $1700-2950.

I'd be happy to change my tune pending some T&E, though. I like my DI Colts, and I could be wrong. For now, I'll stick with my 6920s/M6s.

[Magic_Salad0892]

I think the only practical application for pistons is in guns with shorter reciever extensions IMHO. Like the SCW, or the 416-C.

For a regular CQBR or M4 setup. I think DI is the rule of the day.

[sinlessorrow]

Unbelievable. The same people who scream in every other thread that piston systems shouldn't be utilized in the AR-15, that it wasn't designed to take operating systems outside of the Stoner architecture, and/or that piston guns offer up nothing over DI guns...

...are now saying they'll buy one of these and are excited to have it? All based on some pictures? Glad we're consistent in our opinions and objectively evaluate what's presented to us. I'm sure everyone oggling over this would still love it if "Colt" weren't in front of the model designation, right? :rolleyes:

On that note, I'd be anxious to see a torture test of this gun. I don't like how many parts go into the op-rod assembly, nor that pins are required for system take down. On its face, it doesn't seem to offer anything over the piston systems currently available on the market, especially at $1700-2950.

I'd be happy to change my tune pending some T&E, though. I like my DI Colts, and I could be wrong. For now, I'll stick with my 6920s/M6s.

No one has changed their minds. I still don't feel a piston offers any upgrade that are noticeable enough to worth the large increase to change platforms.

I do still want this though just like I want a HK416(not the MR556).

[Suwannee Tim]

It increases the number of smaller, easier to lose, fragile parts. I'm not sure that's a good thing

Look at the guts of some of the modern pistols. I had the trigger mechanism out of an FNP45 recently. Holy smoke it looks complex and fragile!

Except for the insert in the upper it looks a lot like an LMT which looks a lot like an Adams, pretty straightforward stuff. No surprises.

[Tokarev]

The piston rod broke during a firing string creating a single shot wonder. the rod snapped about 1 inch in from the receiver. As only the bottom rail is removable I had to send it back to Colt for repair.


I assume that if you had the older two piece carrier, etc Colt will replace/is replacing these with the new parts.

What kind of round count did you have before the piston rod broke? Did you shoot a steady diet of M193 in it or anything like that?

[Magic_Salad0892]

Look at the guts of some of the modern pistols. I had the trigger mechanism out of an FNP45 recently. Holy smoke it looks complex and fragile!

I can hear laughing from afar... and it is the laugh of an HKP7....

[MistWolf]

Look at the guts of some of the modern pistols. I had the trigger mechanism out of an FNP45 recently. Holy smoke it looks complex and fragile!

Except for the insert in the upper it looks a lot like an LMT which looks a lot like an Adams, pretty straightforward stuff. No surprises.

I know. I have a PPQ. Walther also doesn't want the average shooter to do more than remove the slide, recoil spring and barrel.

Keep in mind the small parts are part of the original design of the pistol, not retro-fitted


Unbelievable. The same people who scream in every other thread that piston systems shouldn't be utilized in the AR-15,...are now saying they'll buy one of these and are excited to have it?...

Amen, brother

[Arctic1]

Of course, the more complex the machine, the more complex the parts. A machinegun has more small parts than an infantry rifle and an aircraft has more small parts than a machinegun. I agree training is an excellent answer. My point is, other op-rod conversions get raked over the coals for adding complexity to the AR. This one has even more parts than other AR op-rod systems that I've seen, yet that's ok.

It probably gets a pass because it's a Colt.


I make no claims about wear or early failure on this one. I can tell you from long experience, small parts constantly get mis-placed & lost and the more parts there are, the more likely they get lost. That's why as a technician, it's very important that I keep the work area and the parts neat, organized and tagged. A soldier in the field does not always have that luxury

You stated that parts could get boogered, I read that as failing or breaking.

I can also tell you from experience that what you are describing regarding soldiers losing parts for their guns during field maintenance is not the rule, rather an exception. Sure, it happens every once in a while, but people aren't losing parts all the time. Also, we usually do not field strip our weapons during firefights, although the one time it did happen for us, our interpreter (local national) did it in the dark, while taking fire (Minimi). He fixed the malfunction and got the weapon running again. I think you give people less credit than they deserve.


I cannot tell you how many times I've read a post about a FAL that won't function only to find out it's due to the gas regulator being out of adjustment, most times because someone had finger fiddled it. I find it interesting that it's not ok to have sights a soldier will fiddle with throw and change zero but it's ok to have a regulator to fiddle with that can turn the rifle off

I don't have any experience with the FAL, so I cannot comment on that particular AGR syste,. I have had no bad experiences with the adjustable gas system weapons I have used; HK416, HK417, FN MAG, Minimi. Like I said, the system needs to work properly. I am not caliming that there are AGRs with less then stellar designs out there.
And I guess I'm not privvy to the discussion about soldiers fiddling with sights, so I don't understand your example.


I like changes that make my gadgets operate better, easier to maintain or improve safety. This innovation doesn't do any of those. As a technician, I see potential problem areas on this new piston/op-rod that I would be keeping a close eye on until they've proven themselves

Well, can you quantify that with hard numbers? Or is it just conjecture? It should be very easy to test in this case, by running a side-by-side comparison of a regular 6940 and the 6940P. They are identical, except for how they unlock the bolt.


I'm not critical because I simply want to hold on to what I like. I'm critical because historically op-rod systems in ARs bring no practical improvement over the original. What does this do that the traditional AR gas system does not? What advantage does making the op-rod in several pieces have over a single piece? Nearly every good improvement makes a machine simpler, especially when talking about mature technology. The Colt op-rod system is NOT simpler

Again, where is the quantifiable data that supports your statement? Stating that a piston system is not simpler than direct gas impingement is not fact, it's an opinion. If it does lead to less wear, if it does lead to less time required for maintenance etc, would not that be considered a simpler system?
And I don't know the reason for the three piece system, but they call an "articulating link piston system" on their home page. I am sure that they designed it that way for a reason.

[Magic_Salad0892]

Hey. Can somebody post a pic of the 6940P disconnector?

Or the whole trigger group?

I'm curious as to weather or not it mimics the HK trigger group.

[KiraX105]

What revision was it? The newly modded ones or the older ones.

I don't know what revision it is. I purchased the rifle from my local dealer earlier in 2012. If I were to go off of serial numbers, it's pretty low, just past the 1K mark

Having worked on service rifles for the past 10 years got me torqued that I couldn't just fix it :)

For me its an $1800 novelty and will only get recreational use out of it once it returns from the factory. Or maybe I just got a friday afternoon gun and it'll all be better when it comes back

[MistWolf]

Arctic1,

As an experienced aviation technician, I can tell you that fewer parts to do the same job is simpler. Retrofitting a fully developed and mature machine with more parts to do the same job adds complexity. This is not an opinion, it's a scientific, quantifiable fact. Whether or not the added parts are worth the added complexity is theory until proven.

I cannot prove with hard numbers that an op-rod system does nothing the original system cannot. However, no one has produced hard numbers that it does. The lack of evidence that the op-rod system is an improvement is evidence that it is not, that it simply does the same thing but with added parts.

I do realize that soldiers do not lose parts every time they field strip a weapon. I don't lose parts every time I pull an aircraft apart for inspection & maintenance. If I did, I'd be fired. But it can happen and it does happen, especially with small parts (panel fasteners have a way of disappearing frequently) even after our best efforts to prevent it.

I used the word buggered as in "something can go wrong with the part". It's not always about wear. Sometimes it's due to the guy working on the machine doing something stupid because they are inexperienced, complacent, tired, or plain hamfisted. Again, it does not happen every time, but it happens. Technicians constantly have it pounded in their heads to be careful to avoid such things because He Who Shall Not Be Named (Murphy) is always lurking.

The "fiddling with sights" thing is something that kept popping up during forum discussions involving iron sights. My comment comparing adjustable regulators to iron sights is an observation about our ability to apply one standard to one aspect of our rifle and another standard to another aspect.

In fact, my whole point is about that. I have read and participated in several discussions about AR op-rod systems. In nearly every discussion, the op-rod system gets severely thrashed because
1) It's more complex
2) Contains proprietary parts in a system critical to function
3) Does nothing the original system does not already do

Yet this op-rod system has immediate fans simply because it's introduced by Colt even though it has even more parts than other op-rod systems and looks to do the very same job.

I may be overly skeptical. But if Robinson Helicopters did the same thing, say offer a retrofit kit that installed adjustable lead/lag links to the main rotor hub of the R44, I would wonder what the heck they were smoking. The current system is simpler, needs no adjusting when set up right, is easy to set up and works. Changing the hub to use adjustable lead/lag links would just add unnecessary complexity for no gain.

Whether or not the additional parts of the Colt op-rod system is worth the added complexity remains to be seen. In either case, I remain very amused on this subject

[Arctic1]

@MistWolf:

That is a bit of a stretch, isn't it, claiming that lack of evidence on this matter, equals that a piston system in an AR-15 does nothing better? Like you state yourself, no data has ever been produced. However, and yes I'm gonna use this card, your military's top hostage rescue units use a piston AR. Out of every weapon they have available, they choose that gun. That is anecdotal, at the least.

I'm not saying that all piston designs are equal, but to reject the concept without any data to back it up isn't very open minded.

In this case, it shouldn't be hard to quantify and produce some hard data, seeing as you can get two identical rifles, only with different operating systems.

Since this is about piston ARs, the "golden" standard of piston ARs is the HK416. It really has no more parts than a DI AR-15, when it comes to the way the operating system works. If you are strictly counting parts that is. If you only look at the op-rod and piston, it has one more part, that being the piston itself, than the AR-15 using a gas tube. I find it to be a stretch to say that this difference suddenly makes it a more complex system. Same with the articulating link piston system introduced by Colt in the 6940P. I'm sure that design is there for a reason.

I could always make the argument a piston system is simpler than a DI system, or equally complex as the DI system:

-Simpler, because there is no need for a carrier key, carrier key screws, staking of carrier key screws, no gas rings or bolt tail on bolt to facilitate seal needed to start unlocking the bolt.

-Equally complex as it consists of mostly the same parts, doing the same function, but in different places in the cycle.

Based on my experience, and based on feedback from armorers working on both the C8 and the HK416, the HK416 is more durable. Less parts in need of replacing, less frequently. I think the piston system, among other features, contribute to that. The HK416 is also easier to maintain. This means less time spent on field maintenance, for example, and more time to eat, rest, sleep.

Wether or not these things count as beneficial or not, will always be a matter of perspective. Also, this is not saying that a DI weapon isn't cut out for the job. It clearly is.

The fact that small parts are easier to lose than larger ones still doesn't make it a huge issue, and like I stated earlier, the cotter pin is A LOT smaller than the parts of the piston system the 6940P. I have seen more weapons non-op due to parts breakage than to losing parts.

And yes, people sometimes do things they should not. I think removing the human aspect of this is impossible, you cannot safguard against every thinkable occurrence. That is why we use checks and inspections, and properly supervise these in order to reduce the likelyhood of unwanted occurrences happening.

And why should people not be allowed to be exited about this product? Colt is regarded as a known quality on this board. Should they not be allowed to hope that Colt puts out a product that works well? Surely people are allowed to change their minds on different subjects?

One thing that has caught my eye is that many detractors of the piston AR has probably never even fired one. Many people default to the standard arguments that you have listed, and just parrot what they have read others state on the internet. People are of course allowed to be critical, but being critical on principle rather than basing criticism on either hard data or personal experience is narrow minded, in my opinion.

I would sincerely like to see an identical head to head test of two very similar weapon systems, like the 6940 and the 6940P carbines. Everything documented, with intervals for checking certain features like wear, parts breakage, accuracy etc, and logging all malfunctions and causes. Identical lube and cleaning intervals.

Although I have contributed to this in this thread, I think it is a shame that whenever a piston gun thread shows up, it always turns into a piston-bashing fest or piston vs. DI discussion, rather than discussing the weapon the thread is about. No need to rehash the anti-piston argument in every thread.

[sinlessorrow]

I think a 6940 vs a 6940P would be one of the best piston vs DI comparisons as the ONLY difference is opersting system unlike some systems that use stronger materials, different costing, ect.

While Delta and DEVGRU use the HK416, which I am sure is for a reason they also use the Eotech 551 whcih again is for a reason.

I point this out to show that without numbers just saying oh this group uses this does not really end the discussion, we all know Eotech sucks, we all know the 551 sucks even harder, yet the 551 was used to slay OBL.(this is not me sayig the 416 sucks so dont twist my words if someone planned to).

Once the IC finishes we can finally see how DI stands up to a piston sytem, from what I hear there is also more competiting that what Matthew Cox(lol) has said.

If a piston ends up winning and being adopted I will gladly pick one up, but ATM the data is not there and parts are hard to find for proprietary systems and generally 3 times as much.

[MistWolf]

Arctic1, just to be clear-

I don't claim the op-rod system is less durable or reliable. I like plenty of rifles that have op-rods. You make a good point about the separate gas key and staking.

I am asking questions about the articulated op-rod because in my experience, parts that look like that in similar applications are trouble. That is a theory based on experience. I'm willing to have my skepticism proven wrong if the system proves reliable.

In my line of work, a lack of evidence that retrofitting a more complex system has made an improvement is evidence that there is no improvement. Substituting a three piece brake rotor for a one piece brake rotor with no improvement in braking means the added cost brought no benefit.

I have no experience with the HK416. I trust your experience and integrity and I trust your observations about the HK416. I hope you understand that. You make very good points and I respect and appreciate that. It makes me think.

I didn't make my observations to bash the op-rod system. I have my opinion about the op-rod system which are important only to myself. It's not the excitement for a new system that amuses me- that all well and good actually. Just we (myself especially) sometimes need to step back and see if we are looking at something honestly

[Tokarev]

Well, guys, I'm happy to say that I got the chance to fire the rifle this morning. Range time was limited and I didn't get to do all I wanted but I should have a good enough zero going that the rifle won't take too much tweaking when I finally do get it on paper.

Range work consisted of firing for "zero" on a 10” steel plate at 50 and 100 yards and then firing a few distance transition drills on these targets. After this, I stuck the upper on a select-fire lower and finished off the remainder of the first magazine by running a few 2- and 3-rd bursts. I finished off the morning with a 30rd full-auto mag dump.

Overall, the gun feels smooth and really doesn't feel any different than a Colt 6920. No surprise there. On full-auto, the gun seems gassed appropriately and the cyclic felt and sounded about like it does with a DI gun.

Total round count so far is only sixty rounds. Ammo used was Wolf 62gr FMJ.

More to come....

[Tokarev]

Here are some photos I stole off gunbroker showing the older piston rod and bolt carrier. Note the two piece bolt carrier.

http://img.photobucket.com/albums/v221/tokarev/pix525743129_zps99a05ea3.jpg

http://img.photobucket.com/albums/v221/tokarev/pix788023181_zpsf319dfbb.jpg

http://img.photobucket.com/albums/v221/tokarev/pix080586540_zps16187dfb.jpg

[Tokarev]

As requested. Pics of the new bolt carrier strike face. The impact surface is flat unlike some other designs that use a concave impact point.

http://img.photobucket.com/albums/v221/tokarev/P1020025_zps1123cf2d.jpg
http://img.photobucket.com/albums/v221/tokarev/P1020023_zpsb6a00b65.jpg

[Magic_Salad0892]

Thanks for the pics Tokarev.

Can you throw one up of the disconnector, or trigger group?

[Tokarev]

Thanks for the pics Tokarev.

Can you throw one up of the disconnector, or trigger group?

Yep. I'll do that later today.

[El Pistolero]

Thanks for the pics Tokarev.

Can you throw one up of the disconnector, or trigger group?

Is the FCG different than a regular 6940 or 6920?

[Tokarev]

Is the FCG different than a regular 6940 or 6920?

I don't beleive so but I'll take a close look this evening.

[El Pistolero]

Well I was under the impression that the lower is the same as a 6920 or 6940 save for a different rollmark.

[Tokarev]

Well I was under the impression that the lower is the same as a 6920 or 6940 save for a different rollmark.

I do beleive that is the case.

I do know the rifle shipped with an H2 buffer and has the DIAS block in the lower. I'll take a close look at the trigger group but I'm going to say right now that it's standard semi-auto parts.

[skydivr]

I do beleive that is the case.

I do know the rifle shipped with an H2 buffer and has the DIAS block in the lower. I'll take a close look at the trigger group but I'm going to say right now that it's standard semi-auto parts.

It's standard; I swapped with an SSA a few days ago...

[Magic_Salad0892]

Is the FCG different than a regular 6940 or 6920?

I don't know. I'm trying to find out.

The reason I'm asking is because HK's is because of the force of the BCG striking the hammer, was causing the disconnector to break in the earlier 416s.

I was curious if Colt has a different disconnector like the newer HK guns.

[Magic_Salad0892]

Yep. I'll do that later today.

Thanks. :)

[sinlessorrow]

I don't know. I'm trying to find out.

The reason I'm asking is because HK's is because of the force of the BCG striking the hammer, was causing the disconnector to break in the earlier 416s.

I was curious if Colt has a different disconnector like the newer HK guns.

Thats because even with a 8.5lb action spring and a 5.3oz buffer the HK416 still runs at 950RPM

[Magic_Salad0892]

Thats because even with a 8.5lb action spring and a 5.3oz buffer the HK416 still runs at 950RPM

What does the Colt run at?

[sinlessorrow]

What does the Colt run at?

750-900 but the difference is the force of unlockig, the HK416 unlocks harder which is why it requires such a heavy spring and buffer. If you overgassed a M4 and slapped in a 9lb spring and a 5.3oz buffer and got it down to 950RPM it would probably experience the same issues.

[Tokarev]

Sorry. Home late now so no good light for photos. I'll see if I have better luck tomorrow.

[Arctic1]

I don't know. I'm trying to find out.

The reason I'm asking is because HK's is because of the force of the BCG striking the hammer, was causing the disconnector to break in the earlier 416s.

I was curious if Colt has a different disconnector like the newer HK guns.

The disconnector is not different, they have incorporated a bridge plate to protect the disconnector tail from the hammer strike during the cocking phase:

http://img341.imageshack.us/img341/535/p3240006a.jpg
http://img15.imageshack.us/img15/3667/p3240007a.jpg

This bridge plate is a standard feature on the 2-stage trigger from HK seen in the MR556 series, the MR762 series, the HK417, the HK416S and in the upgraded HK416N as well as the new guns we are getting. I would think that the HK416A5 has it as well.

[Magic_Salad0892]

Arctic1:

Thanks for correcting me. Sorry for the misinfo.

[Arctic1]

No worries.

Also, to clarify, the broken disconnector issue was only seen in the 10.5" guns, for us at least.

[Tokarev]

Cell phone and a flashlight actually worked rather well. I'm surprised.

Anyway, there doesn't appear to be anything different or unusual about the lower parts kit. I'm rather surprised by the notched hammer but I guess it doesn't do anything since the firing pin is shrouded.


http://img.photobucket.com/albums/v221/tokarev/utf-8BSU1HLTIwMTMwMjI4LTAwMzQ2LmpwZw_zps5d93b2c5.jpg

http://img.photobucket.com/albums/v221/tokarev/utf-8BSU1HLTIwMTMwMjI4LTAwMzQ3LmpwZw_zps381f525a.jpg

http://img.photobucket.com/albums/v221/tokarev/utf-8BSU1HLTIwMTMwMjI4LTAwMzQ4LmpwZw_zpscb9e5ed5.jpg

[Displaced Texan]

Pretty standard Colt lower...