View Full Version : Internal workings of the HK416 bolt carrier group: Pictures
Photos taken by Turbo-j over on the HKPRO boards. Many thanks for his permission to post these here. I thought some of you might find this interesting. Below are photos of the firing pin safety and associated parts removed from the HK416 bolt carrier. Really gives you an idea how it works if you've never handled one.
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1076.jpg
From top to bottom: Generation 2 bolt carrier, Generation 2 bolt carrier with firing pin safety removed, Generation 1 bolt carrier
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1077.jpg
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1078.jpg
HK416 bolt carrier comparison to standard Direct Impingement AR bolt carrier
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1079.jpg
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1080.jpg
Top: Generation 1 bolt carrier, Bottom: Generation 2 bolt carrier with firing pin spring and safety. Note the updated firing pin head and change in bolt design.
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1081.jpg
Top: Generation 1 bolt carrier, Bottom: Standard DI AR bolt carrier
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1083.jpg
Firing pin safety and firing pin safety spring removed. Note the two pins used to hold the safety in place.
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1086.jpg
Hammer on Geissele trigger group. Not tall enough to disengage the firing pin safety.
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1087.jpg
Standard AR hammer without notched cutout, correct height to disengage the firing pin safety
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1088.jpg
Here's how the safety rests in relation to the firing pin while in the carrier. The firing pin spring rests in the back portion of the bolt, putting tension on the firing pin so it can engage with the firing pin safety after each shot.
Another thanks to Turbo-j for the great pics.
Tspeis
Apparently, I sleep under a rock or something....when and WHY did HK decide to do this?? Seems unnecessary.
Seth Harness
04-12-08, 22:16
Interesting... Thanx!
Seth Harness
04-12-08, 22:19
Apparently, I sleep under a rock or something....when and WHY did HK decide to do this?? Seems unnecessary.
Got to hand it to the germans. They're always thinking, Necessary or not. :D
Apparently, I sleep under a rock or something....when and WHY did HK decide to do this?? Seems unnecessary.
kinda what im thinking. this thread just knocked HK off of any list of mine they could have possibly been on in regards to pistons and ARs.
nothing like having a WHOLE GRIP of non-standard parts and potential failure points to make it a pain in the ass.
tspeis..small correction on last picture describing operation of firing pin safety lever..the firing pin spring(big spring) keeps tension on bolt head to keep it forward and keeps firing pin pressed against the "bolt carrier pin", (dont know if its the right definition), but its the cotter pin that releases the firing pin from bolt carrier...it does not keep tension on firing pin safety lever..if it did it would actually push up the firing pin safety lever up.
what keeps tension on firing pin safety lever is the small spring, it pushes lever down..the firing pin safety lever pin piviots on small hole, the big hole is to allow up and down movement of the firing pin safety lever...
to release firing pin safety lever,(im gonna call it FPSL, to long to type every time) ar15 hammer must first strike FPSL, moving it upward, allowing hammer to strike firing pin, firing pin stirkes round, and once hammer is cocked back, FPSL drops back down..
it is the small notch on the bottom of FPSL, that must clear in order for the firing pin to move forward..
I should have been a little more clear. The spring that captivates the firing pin pushes the firing pin to the rear after each shot so that the firing pin safety can reengage with it.
Thanks again for the pics Turbo-j.
Tspeis
kinda what im thinking. this thread just knocked HK off of any list of mine they could have possibly been on in regards to pistons and ARs.
nothing like having a WHOLE GRIP of non-standard parts and potential failure points to make it a pain in the ass.
For what it's worth, the Bushmaster ACR will have a similar safety device incorporated into the bolt carrier. Just food for thought. In all the endurance tests the HK416 has been through, this safety has never been cause for concern. Lastly, the "WHOLE GRIP" is not made up of non-standard parts. The 416 utilizes standard AR lowers.
Apparently, I sleep under a rock or something....when and WHY did HK decide to do this?? Seems unnecessary.
Since 2004 I believe. There were issues with slam fires being experienced due to soft primers with some frangible ammo. The stronger buffer spring, heavier bolt, and lack of gas rings also contribute to increased carrier velocity during cycling, which could cause a slam fire as well. That's why HK added the safety. The stronger buffer spring and bolt design help to improve function and the issues of slam firing are gone with the firing pin safety. FYI the firing pin safety has no effect on reliable operation of the weapon.
Tspeis
Derek_Connor
04-13-08, 07:28
Damn, good info. I thought the only thing out of spec was the BCG, but now certain triggers cannot be used with the HKs...wow
Damn, good info. I thought the only thing out of spec was the BCG, but now certain triggers cannot be used with the HKs...wow
the issues about which triggers can be used with the hk416 was the reason for this post on hkpro.com...
heres the link..i dont feel like typing again..
http://hkpro.com/forum/showthread.php?t=80049
http://i21.photobucket.com/albums/b258/Turbo-J/CIMG1088.jpg
I can't tell you how many times I've had my bolt carrier group apart, and said to myself, "This design is pretty good, but you know what it really needs to be just right? Several extra parts.'
I can't tell you how many times I've had my bolt carrier group apart, and said to myself, "This design is pretty good, but you know what it really needs to be just right? Several extra parts.'
EXACTLY:rolleyes:
militarymoron
04-13-08, 11:36
The stronger buffer spring, heavier bolt, and lack of gas rings also contribute to increased carrier velocity during cycling, which could cause a slam fire as well.
increased bolt velocity (relative to the carrier) due to removal of gas rings in some piston is what prompted me to bring this up in the PWS piston thread - it might be better to re-install the gas rings to provide some resistance (like the HK firing pin spring) to also reduce cam pin slam.
increased bolt velocity (relative to the carrier) due to removal of gas rings in some piston is what prompted me to bring this up in the PWS piston thread - it might be better to re-install the gas rings to provide some resistance (like the HK firing pin spring) to also reduce cam pin slam.
Due to the design of the bolt, gas rings cannot be installed.
Tspeis
I can't tell you how many times I've had my bolt carrier group apart, and said to myself, "This design is pretty good, but you know what it really needs to be just right? Several extra parts.'
As Tspeis explained, the block was designed because older HKM4/416 carbines were experiencing slamfires. The gun was literally designed around green tip and had a variety of problems with other ammo early on.
While I agree that theoretically more parts means more chance for trouble, there are certainly a number of guns on the market with firing pin block mechanisms which aren't troublesome. There is also a benefit from the procurement officer standpoint in being able to say "this gun is more drop-safe" etc.
militarymoron
04-13-08, 12:27
Due to the design of the bolt, gas rings cannot be installed.
Tspeis
i was referring to other conversions/designs that use standard bolts, not the 416.
As Tspeis explained, the block was designed because older HKM4/416 carbines were experiencing slamfires.
I'm curious as to WHY though. I've seen no indication its a problem that plagues the D.I. set up.
maybe the WEIGHT of the HK firing pin is more than standard. and maybe higher carrier speed somehow. both of those things would increase the force that the pin would exert on the primer when coming into battery.
:confused:
no gas rings on the bolt will decrease friction, as tspsis says, possibly increasing carrier speed as it comes home....he also mentions heavier recoil spring.
I am planning on keeping my gas rings in place with the PWS system.
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