Colt 6940P--Piston Parts Pics

[usbp379]

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.

[Stickman]

Thanks for sharing this, if you get a chance can you shoot more pictures and include the BCG?

[usbp379]

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

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

[Paulo_Santos]

I like it. Looks similar to the LMT.

[MoxyDave]

Very interesting. Thanks for the photos and writeup.

[usbp379]

Well, guys, I'm happy to say that I got the chance to fire the rifle the other 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....

[usbp379]

I like it. Looks similar to the LMT.

Yes. Pretty similar system except the Colt transfer rod and piston are held together with a swivel joint. And, of course, the Colt doesn't have any provision for the QD barrel. No suppressor setting on the Colt, either.