View Full Version : You know those 6940P "press fit" carrier key screws?
Apparently they aren't. I got the new one piece carrier and longer op-rod from Colt, so I decided to see if I could make the original carrier into a DI one.
I remember reading a thread here about a year ago that someone in it said the carrier key screws had special "press fit" pins in them to prevent shearing. Well, the screws came out with a little muscle (they weren't staked). As it turns out the key has a protrusion on it that goes down into the gas hole of the carrier providing a third anchor point in addition to the screws. Turned the carrier upside down and put the key in a vice, then used a mallet and smacked on the rear side of the carrier. It slowly turned so I basically twisted it back and forth until the carrier came free.
Not sure what all that "press fit" stuff was about but getting the solid piston carrier key off wasn't all that hard. Now I have a DI carrier key kit coming from Bravo Co. and will then have an extra DI carrier!
Littlelebowski
06-23-13, 18:30
This thread needs pics.
This thread needs pics.
The screws look like regular key screws. The key is solid (no gas tube hole) and except for a "pin" protruding downward from where the gas hole is it looks the same as a DI.
LWRC used a similar type of setup back before their one piece carrier came out.
SpankMonkey
06-23-13, 21:02
This thread needs pics.
This...
I believe the OP took a piston bolt carrier and removed the solid key from said bolt carrier by twisting off the said bolt carrier from the solid key that was secured in a vise. But not before whacking it with a mallet! He has a BCM Gas Key in route and will install said gas key onto the carrier that he had previously removed the solid key from and "Voila", he will then have a spare bolt carrier that can be used in a direct impingement carbine. :D
I believe this is the carrier in question
http://www.gandrtactical.com/images/archive/Colt/6940P_BCG.jpg
The "press fit pin" was info from someone at Colt IIRC.
Heres the original 6940p thread in all it's glory
https://www.m4carbine.net/showthread.php?t=101299
justin_247
06-23-13, 22:41
There are two different variants of the 6940P, so I'm interested, as well...
http://www.weaponevolution.com/forum/showthread.php?4714-Colt-6940P-Piston-Parts-Pics
http://www.ar15.com/archive/topic.html?b=2&f=29&t=217533
I believe the OP took a piston bolt carrier and removed the solid key from said bolt carrier by twisting off the said bolt carrier from the solid key that was secured in a vise. But not before whacking it with a mallet! He has a BCM Gas Key in route and will install said gas key onto the carrier that he had previously removed the solid key from and "Voila", he will then have a spare bolt carrier that can be used in a direct impingement carbine. :D
Yeah, basically. There were 3 "anchoring" points: the 2 screws, and then a protrusion beneath the faux key where the gas would normally come in on a DI gun. Removed the screws, then twisted it until the protrusion broke free from it's friction hold.
I'll try to get a pic up later (Dr. appointment this morning).
Point was that the screws were supposedly "press fit" with a pin in the middle of each of them them that essentially made them homogenous with the rest of the carrier, sort of a permanent attachment. This was ostensibly to prevent shearing from the op-rod hitting the carrier. Removing with as little difficulty as they did indicates to me that they were NOT press fit into place. i.e. good thing Colt went to the one piece carrier.
The link someone posted above to the M4Carbine thread about the 6940P shows a diagram of what the press fit pins would look like.
Here ya go.
http://i222.photobucket.com/albums/dd187/ABNAK/carrier009_zps28046953.jpg (http://s222.photobucket.com/user/ABNAK/media/carrier009_zps28046953.jpg.html)
The "press fit pin" was info from someone at Colt IIRC.
Heres the original 6940p thread in all it's glory
https://www.m4carbine.net/showthread.php?t=101299
The first post on page 6 of that thread has the press fit pin schematic (originally posted by sinlessorrow).
justin_247
06-24-13, 12:34
The first post on page 6 of that thread has the press fit pin schematic (originally posted by sinlessorrow).
That's just a general concept picture... it's not a "schematic" from this weapon.
BTW, great pics!!! Very informative.
That's just a general concept picture... it's not a "schematic" from this weapon.
BTW, great pics!!! Very informative.
You can't be serious about the pics......crappy cellphone shot! Matthew Brady I'm not! Nonetheless you can see the three holes: two for the screws and one where the protrusion went (and also where the gas goes into the carrier in DI mode).
Yeah, those schematics were conceptual. However, if it was done I shouldn't have been able to remove those screws.
justin_247
06-24-13, 14:12
You can't be serious about the pics......crappy cellphone shot! Matthew Brady I'm not! Nonetheless you can see the three holes: two for the screws and one where the protrusion went (and also where the gas goes into the carrier in DI mode).
Yeah, those schematics were conceptual. However, if it was done I shouldn't have been able to remove those screws.
These were the first pics I've seen of a disassembled 6940P bolt carrier... your cell phone worked great! I couldn't ask for more. :)
Displaced Texan
06-24-13, 14:13
That may be why Colt switched to a one piece carrier design in later versions of the 6940P.
Apparently they aren't. I got the new one piece carrier and longer op-rod from Colt, so I decided to see if I could make the original carrier into a DI one.
I remember reading a thread here about a year ago that someone in it said the carrier key screws had special "press fit" pins in them to prevent shearing. Well, the screws came out with a little muscle (they weren't staked). As it turns out the key has a protrusion on it that goes down into the gas hole of the carrier providing a third anchor point in addition to the screws. Turned the carrier upside down and put the key in a vice, then used a mallet and smacked on the rear side of the carrier. It slowly turned so I basically twisted it back and forth until the carrier came free.
Not sure what all that "press fit" stuff was about but getting the solid piston carrier key off wasn't all that hard. Now I have a DI carrier key kit coming from Bravo Co. and will then have an extra DI carrier!
You would have been better off leaving the factory Colt carrier assembled.
You would have been better off leaving the factory Colt carrier assembled.
Why do you say that
You would have been better off leaving the factory Colt carrier assembled.
Well, I have two new USGI bolts from Specialized Armament just screaming for a home! I can help at least one of them out this way! ;)
That may be why Colt switched to a one piece carrier design in later versions of the 6940P.
True dat!
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