View Full Version : Do I need to replace this gas key?
I picked up a Sionics NP3 bcg second hand and the gas key has minor damage around the gas tube interface. Do I need to replace the gas key or is it not a big deal? I checked it on my upper and it closes and didn't appear to get caught up on anything.
https://live.staticflickr.com/65535/51013477617_3b258ef423_k.jpg (https://flic.kr/p/2kHTpBx)
https://live.staticflickr.com/65535/51013477612_6492c0d732_k.jpg (https://flic.kr/p/2kHTpBs)
Inkslinger
03-07-21, 13:44
Does it go fully into battery? Put it in the rifle and try it out. Shoot it. If you have no malfunction then you probably don’t need to worry.
Yikes, must have landed just right on a very hard surface.
If it was mine I would replace it, or at least try to bend it back to normal, for peace of mind.
Mark
The fourth law is that a dropped carrier will land on its gas key just as sure as toast lands butter side down. It's a very common problem that can be fixed. If it's not hanging up there's no reason to worry about it.
What will happen is that your gas tube will start getting eaten away very slowly at the contact point. Too slow to notice most likely, but by the time you do notice, you will be swapping out your tube and key.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
What he said
titsonritz
03-07-21, 19:08
This is why BCGs with integral gas key are some stupid shit. One of the things IG had his classes do was to strip down the BCG and install the carrier only and run it back and forth with your pinky finger to feel how the key was engagng the gas tube, it should be super smooth with no hang-ups, I'd bet performing that test you'd feel it. I'd replace the key, the screws with some OCKS and stake it with a MOACKS.
556BlackRifle
03-07-21, 20:47
Yeah it might work for a while but I agree, best to replace it.
Replacement is not necessary.
HOWEVER -
It should be repaired:
https://i.imgur.com/jVx1KQO.png
ViniVidivici
03-08-21, 00:56
Replacement is not necessary.
HOWEVER -
It should be repaired:
https://i.imgur.com/jVx1KQO.png
That's what I'd do.
Replacement is not necessary.
HOWEVER -
It should be repaired:
https://i.imgur.com/jVx1KQO.png
What tool are these instructions for?
What tool are these instructions for?
Key, Machine, P/N 12926769 (5313-01-310-0370)
Or, you can make your own, see Appendix E, page E-2, of TM 9-1005-249-23&P (dated 19 June 1991), available online, just google it.
(That Appendix has a few good tools, BTW.)
Could you use something like this?
https://cajungunworks.com/product/sp-forged-steel-starter-punch/
I forgot that i had this punch.
https://www.starrett.com/metrology/product-detail/264E
I’m going to see if I can fix it, but if not I’ll replace it. I had already planned to pick up a MOACKS from Ned at some point, just haven’t needed to yet.
ViniVidivici
03-08-21, 20:06
That would probably work.
I personally would buy a small piece of delrin plastic rod and shape it to the key. A few taps with that won’t mar it and it’s strong enough to get it fixed
Either of those punches should work, as long as you don't go crazy beating on the key.
Delrin? I doubt that's not going to be hard enough.
titsonritz
03-09-21, 10:39
Delrin? I doubt that's not going to be hard enough.
That's what I was thinking.
Replacement is not necessary.
HOWEVER -
It should be repaired:
THANK YOU!!
I'd fish around in my garage/bench for something that matched the angle and just tap it back into shape.
Last night I stripped down the Sionics, an FCD, and a Hodge bcg and worked them back and forth in my upper. They all felt identical.
The center punch I linked has too steep of a taper and would open up the bore of the gas key tube before repairing the rim. But the blunt end of my other Starrett punches is almost the perfect fit. So I’m going to use the blunt end of my largest punch to try to gently tap it back it to form.
Thanks for all the assistance gentlemen.
Last night I stripped down the Sionics, an FCD, and a Hodge bcg and worked them back and forth in my upper. They all felt identical.
The center punch I linked has too steep of a taper and would open up the bore of the gas key tube before repairing the rim. But the blunt end of my other Starrett punches is almost the perfect fit. So I’m going to use the blunt end of my largest punch to try to gently tap it back it to form.
Thanks for all the assistance gentlemen.
I've tried using a normal punch before and it didn't work. If you're going to do it, I would use the official gas key punch. If you botch it, replacing the gas key is very difficult and requires pretty expensive tools and some knowhow too.
Glock9mm1990
03-19-21, 12:03
Honestly I would try to contact Sionics and see what they say, I would defiantly want to replace that gas key myself.
Honestly I would try to contact Sionics and see what they say, I would defiantly want to replace that gas key myself.
I bought this second hand so I don’t expect them to do anything about it. I assume they would help me get it sorted, but replacing a gas key is simple enough I can handle it myself.
I did end up reforming the rim of the gas key tube and mostly removing the dent. I don’t believe it will cause an issue in use. I’ll post pics later to get everybody’s opinions.
https://live.staticflickr.com/65535/51055198238_0e2bd474f2_k.jpg (https://flic.kr/p/2kMzeGA)
There is enough english left in the gas key to function with the gas tube IF it passes the function check. Issues most often derive from the milspec barrel nut being off alignment causing gas tube issues. I tighten the milspec barrel nut with anti seize, once and loosen and again to 60ft lbs and keep torquing until the gas tube floats in the upper opening evenly. You then slide the BCG without the charging handle into the upper and look to see if the BCG aligns with the key to gas tube without binding and deflection. Gentle finger pressure should be adequate and the gas tube should not bind or move much as it enters the gas key. It typically moves slightly but when cycling it will not wear the tube “mushroom.” If you see the gas tube deflecting or feel binding adjust the gas tube to align via the barrel nut again and recheck. If it still binds, you may need a gas key. It appears to be fine in that it doesn't seem to be deformed enough to warrant a replacement. Make sure you replace it properly if you do need to. Use good milspec screws a chrome coated gas key, torque it properly and stake it well. If you do not stake with a jig or traditional punch method, I recommend using a triple stake method equal distanced on each screw with a small punch: prouding a good amount of gas key material into the screw as you can without getting too sloppy. I have a custom jig and a big pointy punch for staking needs which resembles the Colt Defense staking method. I had a Colt Match Carbine from the factory with the gas tube poorly aligned enough so that I replaced the tube and realigned the barrel nut. It was in fact wearing into the gas key unevenly. The same carbine had a deformed BC that wore unevenly as it cycled the FCG. At some point the firing pin retaining pin had a catastrophic meltdown and the firing pin jesttisoned back into the upper causing the BCG to bind making it nearly impossible to remove. The cam pin was driven into the upper in the process causing minor surface damage. I replaced the firing pin, cam pin, and firing pin retaining pin after removing the debris jamming the BCG. Fortunately the upper was only cosmetically damaged internally in the process. This is one of the most dangerous failures that can happen when you lose your cam pin. If you forget to assemble the cam pin I have read it can be a fatal mistake and cause the upper to grenade: of the many malfunctions I have seen I have luckily not seen this. In my case the cam pin remained in the track of the upper albeit in a state of chaos.
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