So I'm having a problem with my clone G3 (Century  C91). It's not going into battery correctly. Sometimes it will work, but more often than not, the bolt will not fully return to battery. Sometimes it works when I slap it, but during normal firing, it jams. I feel comfortable replacing what needs to be replaced, but I'm not sure where to start. The little bit I was able to glean from Googling told me that I need a larger gap between my bolt and carrier when the rifle is in battery. It appears I have no gap, but I'm not sure what to replace to fix this issue. Can anyone assist me with fixing this? :)

I'm unsure on the round count on the rifle. I bought it from a buddy who got it from a buddy whose uncle's newphew's former roommate's side hall neighbor from way-back-when etc etc. Needless to say, it's seen quite a few rounds. I haven't noticed anything amiss when I break it down, other than the bolt head locking lever being very stiff when I'm putting it back together.

I'm sorry if this is in the wrong spot!




I can provide more pictures if needed.

Thanks a bunch!

When you say that it is hard to put do you mean just unlocking as within the first inch of the pull or the whole pull?

Have you actually measured your bolt gap with a feeler gauge?

Just looking at the photo it seems you have enough gap for proper function.

so it will fire when your charge the gun it works but once fired the bolt comes out of battery?

might be bolt bounce
recoil spring might need to be replaced
check mags
that is my guess.

I sadly lack a feeler gauge. It's easy enough to pull back and hand cycle. It's when it jams up (like in the first picture) that I have to slingshot the thing.



Bhouse, it doesn't always return to battery. Sometimes it will cycle just fine, other times it will strip a round off, but the bolt fails to fully seat.
I thought it might have been the rollers sticking (I tried replacing those and it still had the same issue). I've tried three different recoil springs, and all 9 mags that I have (steel and aluminium).

I took a video to show what happens.

https://www.youtube.com/watch?v=ezErYPQw8Kk

It almost acts like its binding somewhere as it works sometimes but not all the time. I would almost bet if you had the rifle facing downward it probably does it less. Like something, it slowing its momentum.

I know you have probably already done this but is the locking piece well lubed. Not that a lack of lube could cause it to be this bad but it does help to have it wet.

Typically most problems with the G3 style rifles are from rollers and locking pcs. But yours almost seems like something was not built right

I say mag issue.

wiggle mag when it does it again and see if it fully seats.

If you're having failures to feed, my first guess would be that the recoil spring is weak and needs replacement. A lot of these rifles use surplus parts with unknown round counts. It's a cheap fix and one probably worth doing anyway, regardless of whether it resolves the issue or not.

My eyes may be tricking me.....but is that a roller dimple in the receiver?

If so your bolt head isn't seating fully before the carrier/locking piece slams those rollers outward

if you take the rifle apart and just have the bolt slide back and forth inside the receiver does it move freely?

might be the receiver is bent.

I still think it probably is bolt bounce (common on G3/Cetme) which is a recoil spring issue just get a brand new one (yes they are expensive but will probably work).

last thing I would check is how freely the bolt moves in the carrier I work with several MP5s (full auto) and have had several where the locking piece for the bolt would seize up from heavy use. Also check the firing pin spring

So I'm sure it's not a mag issue as it's a constant issue across my collection of mags. It still happens if I drop a round in the chamber and drop the bolt.

It feels like it hangs up when the bolt head is about to lock into the trunion. It is possible for that part to get warped?

Villafuego, I think it's a roller dimple? I've taken better pictures, that will hopefully be more clear.

Bhouse1545, the bolt slides back and forth just fine. The bolt locking lever is amazing stiff and it takes a fair amount of swearing and effort to get it to unlock so I can slide the bolt head forward, allowing me to put the bolt assembly back in the receiver. Could a super stiff bolt locking lever spring cause this issue?
The issue occurs with all three recoil springs that I have. The one I have currently installed is the stiffest of the 3.

Where in OR are you?

When you say "the cocking lever is stiff" stiff at the initial flip of the handle that unlocks it or stiff after the handle is flipped and that initial pull like its still locked.

You might need a different roller size or you have too much gap between the carrier and the charging handle. also, I don't see how these issues could cause the problem you are having unless it is indeed something to do with the carrier, bolt or locking pc.

flipping the handle should not be that hard if flipping the handle is hard then your issue is not with the mags and more

If it's hard right at the beginning of the pull after its been flipped it rollers or locking piece is worn. Even a worn cocking handle can make it hard to pull at the start but very easy to flip because is not contacting the bolt well enough but again that would not be the problem with it not going into battery.

ok so if it's stiff your problem is probably in the bolt so maybe change the rollers and locking piece if there is excessive wear also change out the firing pin spring.

Pick up some feeler gauges from hkparts.

They sell feeler gauges at the local auto parts store.

take a picture and post it of the following, the back of the bolt head and the front of the locking piece. your bolt is trying to lock in the receiver and not in your trunnion. No bueno.
get some feeler gauges and check the bolt gap. it should be in the .010-.020 range.
I suspect the bolt head may be one of the century ground bolt heads for artificial bolt gap.
(they ground off the back of the bolt head to get the bolt gap. ) the locking piece may also be very worn and helping to cause the problem.  

we are also going to have to check the cocking tube clearance once we can get the bolt gap measurement. (it should be at least +.010 the bolt gap)

I would consider the gun unsafe to shoot at this point.

Looks like a dimple in the receiver to me, and looks like the rollers are stopping right there. Maybe sometimes the bolt is able to get past it before the locking piece can push them out and lock it up. You should be able to feel it on the inside of the receiver with your finger. Check both sides.

Oh my! I just relooked at the pictures. The one showing the inside of the left side rail is pretty beat up. (The first pic in the 1AM post) That should be smooth as snot, not even scored, much less gouged.

There is metal that is peened/worn away there in multiple spots. It . I don't think there's a fix that will be permanent.

IMO, the gun is a parts gun now for what is salvageable. The cost to replace the receiver will likely be higher than another gun (not from Century! )

Or Harbor Freight if you have one near by only cost a few bucks at most.

No doubt . It appears that the bolt head is hitting something trying to force the bolt head to close and cause the rollers to engage and they are pressing hard against the rails because essentially the rollers are beeing slammed . Maybe an alignment issue with the trunnion and the receiver. but wow in order for it to that it would have to be way off.

Save your money on the feeler gauges for now.

Shoot a pic of the inside of the receiver to ghilliebear2000 (PCS) and he'll tell you what it'll take to fix (I doubt he'll work on a Century receiver, but if it's fixable, he can tell you).

Typically, the peened bolt channel occurs from too much recoil/weak recoil spring resulting in bolt bounce (as alluded to above) in that the bolt hits the buffer hard enough that has it "ricochets" off of the buffer, the bolt head slams into the locking piece, pushing the rollers out. This would normally happen further back in the receiver, towards the buffer.

I don't know for sure, but I'm wondering if this could be due to way out of spec bolt gap or drag on the rollers resulting in pushing the bolt head into the locking piece as it drives forward. As you said, the trunnion orientation could be the culprit, but it would have to be peened there too and would never have run right unless it was WECSOG'd into operation.

That makes sense and should be the starting point.

I think the first step for the op is to get a feeler gauge and measure the gap and go from there. As mentioned they can be bought at an auto parts store, hardware store, HF.

Wow! Thanks for the help folks!

BILLBO, I'm in the Gresham area, couple blocks from MHCC. The initial flip of the handle is the stiff part, after that, the bolt rides just fine in the receiver. I may have overstated the difficulty of it, heh. I tried replacing the rollers with smaller ones. It made the issue better than when it was before, but not 100%.

I picked up a feeler gauge today and found that the .010 would fit, but it took some effort to get it to slide in. The .009 slid in just fine though.

Wildweasel, will these pictures work?






Kletzenklueffer, so you would suggest just selling off the parts instead of getting a new receiver?

From RTG "If you have less than .012  of the gap than you will need to acquire + size rollers which are available on the G3 page of this website. It should be (about .012 - .020 Inch)"

Sound like you need the next size up in rollers which is odd since you said you went down in size or your locking pc is worn. Getting the bolt gap corrected and that back in spec should be the first place to start, though. This should solve your unlocking problem and if the problem is bolt bounce which it is starting to sound like since the rollers are not large enough to lock in place it should solve it too. Or at least rule that out as a possibility.

See if someone seconds that.

Studying the picture it does not look like the bolt is in deep enough to be hitting the side of the trunnion.


Replacing the receiver will require breaking the welds on the trunnion to the receiver with a mill or a drill press. I have used a drill press. Then carefully cutting JUST the weld of the cocking tube there is a sleeve that goes into the receiver and you don't want to cut it then removing and inserting into a new receiver and making sure the alignment is right and rewelding. You'll want to use a heat sink in the cocking tube to keep it from burning through. there are other minor steps involved but you have to be able to or know someone that is able to do the above if you want to replace the receiver.

I occasionally go out to towards Gresham but rarely that far out. If you don't get it figured out and you want to make a trip out to TCGC the next time I head out there we can try and trouble shoot it before you go replacing the rifle or tearing it apart.

ETA

I noticed you are using a what appears to be a Steel G3 mag. Have you tried using the Aluminum G3 mags.  I don't think the differences are enough to cause this problem but it has been suggested that it could be a mag issue.

Get the opinion of a builder. I dont think it will matter what the bolt gap is as long as the rollers are trying to expand in the receiver rails. Itll only keep wearing there. Talk to a pro about the cost of reusing the parts on a ptr receiver, or buy a ptr and use these as spares.


ETA0 corrected for spelling. Fat fingers on a small phone.

Alrighty. Sounds like I need to pop the old rollers back in and get a new locking piece.

FWIW, I'm trying to get it working to sell it. I've had issues with it for a while, and  it moved to the back of the safe. After years of neglect, I figured it was time to fix it up and send it to a new home.