I just received a new bolt and carrier from a respected manufacturer today and the bolt seems to fit extremely tight in the carrier. At first I thought it just needed some lube, but after lubing it and cycling it a handful of time it didn’t seem to get any better and I’m getting malfunctions (if you can call them that) just cycling the bolt by hand. The bolt fails to fully lock into battery on the return trip about 50% of the time, and jams unlocking about 75% of the time. Also, shouldn’t the bolt basically slide out of the carrier when you tip it over after removing the cam pin? I need to pull it out with a noticeable amount of force. I don’t believe the bolt or the carrier are out of spec, as they both came from the same reputable manufacturer and I am able to spin the bolt around in the carrier easily with the cam pin removed. I believe the gas rings are staying stationary against the bore of the carrier and the bolt is spinning inside them.
This leads me to think the gas rings are probably the problem, so I’m looking for recommendations on what to do about it. I’m sure I could call the manufacturer tomorrow and I expect they would take care of me immediately, but I want to make sure I’m not just doing something stupid before I trouble them. Do I just need to compress the gas rings somehow, or is there something else I’m missing? It’s definitely not a lubrication problem… by the time I was done messing around with it tonight the only way I could’ve gotten more oil in the thing is by dropping it in a bucket.
I also want to note (in case it matters) that this is not a complete BCG. I purchased the bolt and carrier together, the cam pin is from WMD and tonight’s testing was done without a firing pin because it is still on the way.
Technically, you aren’t getting “malfunctions” as you aren’t actually firing the rifle. It sounds like you have particularly rigid gas rings and the force of just manually cycling the weapon isn’t enough to overcome those rigid gas rings and the bolt isn’t fully going into battery. Bottom line…this probably isn’t a problem. Once you shoot the rifle, those gas rings are going to loosen up/break in. In fact, this is actually a good sign. Loose fitting gas rings are common and not something you want. You want there to be a reasonable amount of resistance in those rings. Lube the bolt liberally (sounds like you’ve done that), go shoot the rifle, and report back. I imagine things will be just fine. best of luck!
EDIT: when you say the weapon “jams” while unlocking 75% of the time…what do you mean? Can you describe what you are experiencing?
Thanks for the reply. What I believe is happening is too much resistance between the bolt and carrier for the carrier to move backward and unlock the bolt when trying to cycle the weapon by hand. I didn’t reef on it super hard, as I don’t want to damage my charging handle, but it’s definitely sticking at about 3/4" of rearward travel. I can remedy this by giving the butt of the stock a hard smack or hitting the forward assist to return the bolt to battery and trying again. Sometimes it cycles, sometimes it sticks.
My .02. You might want to wait to get your firing pin before declaring you have a defective bolt or gas rings. Since the firing pin keeps the cam in the correct position during cycling, it could be that the cam pin is spinning in the BCG and somehow binding the BCG in the upper. In addition, if you can remove the bolt by hand from the BCG there should be no reason why the mechanical advantage of a buffer and spring wouldn’t move it into battery (you’re not riding the CH forward, are you?). You also state that you can get 3/4" of rearward travel. That is about all you need unlock the bolt from the lugs, the rest of the distance is to clear and eject the expended cartridge.
The bolt shouldn’t just fall out. The gas rings need to provide a good seal for the back of the bolt (basically the piston of your action) to operate properly when firing.
Please understand the difference between a “jam”, and a “malfunction”. Seriously. I know on the internet ignorant people will say it is all the same, but it is not. In this case, you aren’t at either.
Here is an easy way to remember things. Jam is spread with a knife. You clear a jam with a tool. A malfunction you clear yourself.
Jam- An interruption in the cycle of operation which requires the use of a tool or the skills of an armorer to clear.
Malfunction- An interruption in the cycle of operation which is cleared by the operator of the weapon.
Actually, as I understand it, the way to test if your gas rings are worn out are if the bolt falls out of the carrier when you tip it. Bolt should stay in the carrier whether you’re holding EITHER the carrier or the bolt 90 degrees to the ground. They should stay together on suction alone.
Make sure when you charge the rifle, you’re not riding the charging handle. Try locking the bolt open and releasing it with the bolt release button. If it’s still not returning to battery, you might have a problem, but you should fire it to make sure anyway. If it returns into battery, you’re fine as long as your bolt travels all the way back when fired.
If i pull the bolt out as far as it goes against the cam pin on a 5.56 bolt carrier group, and stand it on a table, bolt down against the table, and the weight of the carrier will push it down onto the bolt, im replacing the gas rings.
They are too loose, or worn.
If you dont have your firing pin installed, and have the carrier group in the rifle, and are hand cycling it, you really have no way to tell if the cam pin is rotating and causing binding when moving the carrier in either direction.