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AR-15 / M-16 Bolt carrier staking
7.62x39Lover
Member Posts: 3,937 ✭✭✭
Does anybody have any idea why the gas key on AR-15 BCG's are screwed on and then have the screws "staked" in? Rather than just having the key and the carrier be a one piece deal. It seems to me that "staking" is done so that the screws don't walk out, but then it seems you can't unscrew the screws either.
Comments
As far as removing the key. I've replace many of them on M16A1's. Put an allen wrench to the screw and give it some grunt and the stake will come loose.
Operator headspace (dopes who got heavy handed or careless and managed to bend or tweak the gas tube) accounts for a majority of bolt carrier keys I replaced. Once the end of the gas tube is knocked out of alignment the key can't index on it and gets mangled when it hits the end of the gas tube. Dropping the bolt carrier can also bend the key necessitating replacement.
Unless the key is somehow damaged there's no need to remove it. A bit of carbon cutting solvent and a pipe cleaner are all that is needed for cleaning.
I take it the screws walk out easily if not staked? Or can you get away with just putting them on nice and tight? How often / why should the key be removed for cleaning or replacement?
As far as cleaning goes a pipe cleaner does wonders. But it has happened where the opening on the key where the gas tube meets the tube on the key has flared out slightly thus leaking more crud and gas into the carrier. That in itself would require a new key. That and if the gas tube didn't perfectly line up with the key could also cause the key tube to get out of round. Usually happens with a new build.
Does anybody have any idea why the gas key on AR-15 BCG's are screwed on and then have the screws "staked" in?
Cheaper.
quote: Rather than just having the key and the carrier be a one piece deal. It seems to me that "staking" is done so that the screws don't walk out, but then it seems you can't unscrew the screws either.
You can still unscrew them, it just takes more effort.
FWIW, typically the "castle" nut that holds your stock in place is also staked in place to keep it from unscrewing under use.
Edit:
quote:I take it the screws walk out easily if not staked? Or can you get away with just putting them on nice and tight?
I don't think its so much a question of easy/not easy, but rather how bad would it be, if lets say these screws came loose in the middle of a firefight.
Not only would your gun start jamming in potentially unpredictable ways, but with bullets whistling around your head you probably wouldn't have the presence of mind to identify the problem, let alone strip the gun down and actually fix it. Does every soldier have an allen wrench in their pocket? What if the screws popped totally loose and fell into the guns action, or even in the sand?
Do you NEED to stake these screws? Well, as mentioned, some manufacturers don't stake them, yet their guns still function OK. In practice, I think you CAN get away without staking these, its just a question of what's preferable, and how reliable you NEED the gun to be.
Some manufacturers instead secure the screws with red loctite. That's not the same as a mechanical staking, but its still probably better than nothing.
quote:How often / why should the key be removed for cleaning or replacement?
Obviously if the key gets bent or damaged from careless handling or abuse you'd need to replace it.
But under "normal" use, you shouldn't "need" to remove or replace this (ie ever).
Even cleaning isn't necessary on any kind of routine basis. In general the gas system is self-cleaning.
Obviously if it clogs up and the gun starts jamming, you'd clean it, but with ordinary ammo that shouldn't be a normal occurrence. One of the most common causes of that happening is from fouling and lead buildup from using .22 rimfire conversions. In that case you'd either clean the gun or just run some regular .223 through it to blow the crud out of the gas system.
With normal ammo, people will go thousands or tens of thousands of rounds without cleaning the gas port or tube. .
So, ever see a mechanic put a torch to a recalcitrant nut in order to loosen it? Same principle. Joe
So, ever see a mechanic put a torch to a recalcitrant nut in order to loosen it?X-ring.
Due to high heat they require more than just torquing. Mechanically locked (staked) is more postive - while still easily removeable - than any sort of thread locking compound.
In addition locking compound would be just one more required item in that small arms logistical chain which leads all the way out to the most forward postings. An armorer with just a simple tool set and a vise mounted on a vehicle bumper can perform any repairs needed to keep these rifles running.
Bear in mind, most of my experience came with Army M16's.
Operator headspace (dopes who got heavy handed or careless and managed to bend or tweak the gas tube) accounts for a majority of bolt carrier keys I replaced. Once the end of the gas tube is knocked out of alignment the key can't index on it and gets mangled when it hits the end of the gas tube. Dropping the bolt carrier can also bend the key necessitating replacement.
Unless the key is somehow damaged there's no need to remove it. A bit of carbon cutting solvent and a pipe cleaner are all that is needed for cleaning.
Ed Zachary.
Generally, what I see is the carrier key gets damaged from one of two things.....dropping the carrier or the gas tube gets bent.