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Posted: 12/20/2015 10:58:12 PM EDT
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Update:
So we sent the rifle back to Century. Their reply was "the rifle was non-repairable" and they were going to give me the option of shipping it back or giving me a check for the wholesale price of $350. They never gave the explanation of what was actually wrong with the rifle. It seemed shady. So after some back and forth calls and emails, they finally agreed to ship me a new rifle. I can't believe they would ship back a potentially dangerous weapon but after researching Century, their warranty is less than stellar. I guess it worked out for me but may think twice before another Century purchase. I am thankful though that they worked with me in the end. Still not sure what was wrong with it though. -------------------------------------- Just received a NPAP and have problems. Upon firing the bolt was sticking after ejecting after each shot. I researched on the net and found a sticking bolt was common. I polished the rails on the receiver and the guides on the bolt assembly. I also filed a little on the hammer to take the edges off as the hammer has two sharp edges but was careful to leave the face of the hammer flat where it strikes the firing pin. I also applied grease to all these areas. The action was very smooth so I was confident this fixed it. I test fired and no go. Still sticking. Took the dust cover off and found out the bolt is rotating counter clockwise (looking in from the top) and binding in the receiver. This is happening when the bolt is going forward. It ejects the shell just fine. You can rack it all day long by hand and it never jumps out, only when firing. Could the hammer still be too high causing the bolt to jump up and rotate? It has the Tapco trigger. Hopefully my first try at attaching photos works! 
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Quoted:
Just received a NPAP and have problems. Upon firing the bolt was sticking after ejecting after each shot. I researched on the net and found a sticking bolt was common. I polished the rails on the receiver and the guides on the bolt assembly. I also filed a little on the hammer to take the edges off as the hammer has two sharp edges but was careful to leave the face of the hammer flat where it strikes the firing pin. I also applied grease to all these areas. The action was very smooth so I was confident this fixed it. I test fired and no go. Still sticking. Took the dust cover off and found out the bolt is rotating counter clockwise (looking in from the top) and binding in the receiver. This is happening when the bolt is going forward. It ejects the shell just fine. You can rack it all day long by hand and it never jumps out, only when firing. Could the hammer still be too high causing the bolt to jump up and rotate? It has the Tapco trigger. Hopefully my first try at attaching photos works! https://i1204.photobucket.com/albums/bb402/jpitt001/image2_zps7qdwbclq.jpg https://i1204.photobucket.com/albums/bb402/jpitt001/image3_zpsbamphbdb.jpg https://i1204.photobucket.com/albums/bb402/jpitt001/image1_zpsvss9rdtq.jpg something is horribly wrong obviously the bolt cant do what the pic shows can you get a picture of the cavity in the carrier and the bolt lug that fits in this carrier cavity pics of both sides of inside rails? is the bolt shaft fitting in the carrier pretty snug? there are different bolt shaft diameters if someone has the wrong bolt in it (serial number on bolt match carrier serial number and receiver serial number?) |
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Bolt lug fits pretty well in the carrier assembly channel. First AK so not sure how snug or loose it should be but doesn't seem overly sloppy. All numbers match on the rifle.
Side to side magazine play is minimal. Again not alot of experience but nothing appears to me to be abnormal. I have other mags I could try. This is a magpul mag. Is the bolt lug that goes along the left rail supposed to fit under the rail? This one just seems to ride against it. Here's a few more pics. Good pics are hard to take! 
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Quoted:
I polished the rails on the receiver and the guides on the bolt assembly. Something is seriously FUBAR. The bolt physically should not be able to rotate in that location. Where on the rails/guides did you polish? Did you buy it new or used? Don't modify it any more and contact the manufacture for repair, although polishing, etc. may have voided the warranty (hopefully not). Quoted:
Can the bolt be put in wrong? Don't know how you can mess it up as it looks like it only goes one way. But this is my first AK! The bolt and carrier can only be installed one way them to fit into the receiver. |
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Gun was bought used on gunbroker. I used Never dull on the top of the rail and the guides on the bolt carrier. Didn't even rub enough to take any paint off. It did take paint off the hammer where I polished.
On the rails, if you look at the second set of pictures, the third picture does show the very rear of the rail slightly bent upwards. It's even shiny where the carrier has been rubbing. Don't know if that's a big deal buts it's the only thing I could find that looks like unusual wear. The left side is bent slightly upwards as well. Again not a lot but you can tell just by looking that they are bent slightly upwards. |
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Looks like the bolt isn't even in the carrier channel. No way it should be able to rotate like that until it clears the rails and enters the front trunnion.
ETA: I took another look at your first two pics (PS it would help if you rotated those pics 90° CW, BTW) to see what's going on and it looks like you are inserting the bolt and carrier into the receiver without properly installing the bolt into the carrier so that the cam on the bolt is in the cam recess of the carrier. As such you aren't even getting the bolt ears to sit flat on the lower rails and I can see that the lower rail/ejector isn't even in the slot of the bolt. So it looks like you haven't put the thing back together properly. Try again!! See pic below - the left ear of the bolt needs to be bbetween the upper and lower rail. You've got it all effed up. 
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Quoted:
Gun was bought used on gunbroker. I used Never dull on the top of the rail and the guides on the bolt carrier. Didn't even rub enough to take any paint off. It did take paint off the hammer where I polished. On the rails, if you look at the second set of pictures, the third picture does show the very rear of the rail slightly bent upwards. It's even shiny where the carrier has been rubbing. Don't know if that's a big deal buts it's the only thing I could find that looks like unusual wear. The left side is bent slightly upwards as well. Again not a lot but you can tell just by looking that they are bent slightly upwards. I'll get my NPAP out this evening and compare pics and post a few. Thanks |
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Quoted:
Looks like the bolt isn't even in the carrier channel. No way it should be able to rotate like that until it clears the rails and enters the front trunnion. ETA: I took another look at your first two pics (PS it would help if you rotated those pics 90° CW, BTW) to see what's going on and it looks like you are inserting the bolt and carrier into the receiver without properly installing the bolt into the carrier so that the cam on the bolt is in the cam recess of the carrier. As such you aren't even getting the bolt ears to sit flat on the lower rails and I can see that the lower rail/ejector isn't even in the slot of the bolt. So it looks like you haven't put the thing back together properly. Try again!! See pic below - the left ear of the bolt needs to be bbetween the upper and lower rail. You've got it all effed up. http://imageshack.com/a/img910/9105/ZiL22p.jpg It was my understanding it cycles fine by hand. It fires and ejects ok, but when the bolt is rotating on recoil. |
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Can't imagine the OP is improperly assembling if the rifle fires and ejects. OK, I overlooked that part. In that case it may be the receiver is bulged at the rear allowing the bolt to jump clear of the rails and rotate out. This can also be due to the rails not being parallel all the way through to the rear of the receiver and also the rear trunnion being too far back in the receiver. Also might want to check that the bolt isn't hitting the cross member support rivet. |
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I will get some dimensions for you to compare against later today, using my M92. If you have a caliper we should be able to check to see if your receiver rails and bolt head are in spec.
I would guess either the lower rails are too narrow, receiver bowed out, or the bolt lugs are too narrow - maybe even too short. Too much clearance somewhere in there is allowing the bolt to jump off of the rails. Since this is an AK, there's a good chance that one or more of these issues can be resolved by giving the receiver a little squeeze in a vice. We'll see. |
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I looked at it again during lunch and took some measurements. I think the receiver has multiple problems. If you look at the second set of pictures, the bolt lug isn't even between the rails. It's resting on the bottom rail but just sliding against the top rail. In other words, not locked in. I also think my measurements back this up:
Left rail measurements between upper and lower left rail are .243, .24, and .255. The bolt lug measures .265. It's not going to fit let alone have room to slide. Receiver width from upper rail to upper rail from back to front are .95, .88, .79, and .75. Definitely wider in the back but of course the bolt has basically been prying it apart every time it cycles because it's not in between the rails. This is of course my theory based on my measurements but I'll wait to see what you guys think. |
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I'd say that it's over extending inder recoil allowing the bolt to jump track, so to speak, on the guide rails. If it comes back too far this can happen is your recoil spring and guide weak or messed up in any way.
Could you take pictures of the recoil spring and guide? If it's not that or you just haven't completely left the recoil spring out than the rails or receiver are out of spec. |
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Quoted:
I looked at it again during lunch and took some measurements. I think the receiver has multiple problems. If you look at the second set of pictures, the bolt lug isn't even between the rails. It's resting on the bottom rail but just sliding against the top rail. In other words, not locked in. I also think my measurements back this up: Left rail measurements between upper and lower left rail are .243, .24, and .255. The bolt lug measures .265. It's not going to fit let alone have room to slide. Receiver width from upper rail to upper rail from back to front are .95, .88, .79, and .75. Definitely wider in the back but of course the bolt has basically been prying it apart every time it cycles because it's not in between the rails. This is of course my theory based on my measurements but I'll wait to see what you guys think. I dont know how close these plans are for dimensions: http://igor.chudov.com/manuals/AK47/AK-47-Receiver-Blueprint.pdf Here are three views of my NPAP, maybe you'll see something. 
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Although I don't have an NPAP I do have an M92 - same receiver, same bolt carrier/bolt setup (except having a short stem carrier). Only major difference between your rifle and mine is that my M92 has the original factory trigger group.
The ONLY way I could get the bolt to begin to rotate in the carrier similarly to yours, was to pull the carrier fully back. pull up on the carrier, and twist the bolt with my finger. At that point I can see that there is the potential for the bolt to rotate, leave the lower rail at its furthest position at the rear of the receiver, and then jump the rails when moving forward. However this has NEVER happened with my M92. I checked out the receiver rail dimensions and yours is actually a bit tighter than mine, so I don't believe that the rails are out of spec on yours. HOWEVER I can see this happening on your rifle for several reasons, possibly with both combined at once: - Tapco G2 trigger is known for having a very aggressive hammer face profile, and it puts a lot of pressure at the bottom of the bolt carrier. In some cases this may result in the carrier being pushed upwards when it reaches the rear of the receiver, where it enters the section of rail relief slots that are cut to allow carrier removal/installation. In this case you may have just enough upward pressure exerted on the carrier from the G2 hammer to cause this to occur - especially if there is a casting defect in the hammer preventing it from reaching its full range of travel rearwards. I have seen this on some G2 hammers, where there is a "shelf" at the bottom of the hammer that sometimes hits the floor of the receiver. - If you have a weak recoil spring (this has been a known issue in some Zastava rifles) this could exacerbate the above issue, by allowing the carrier to travel far back enough into the area of the carrier relief slots, making the above situation more likely to occur. - Lower rails may have been cut for your receiver just a tad too short, or welded too far forward, allowing this condition to arise easier than on some other rifles - it doesn't look like this is the case in the pictures though. I think the first step is to take a look at the FCG interference issue. Given that the Tapco G2 FCG is known to cause excessive bolt/carrier tail wear on these rifles due to incompatible hammer geometry, I would just go ahead and replace it if possible - I would even seek out the factory Zastava FCG if you can (I believe APEX has them), though this introduces 922r issues. Of course you can also simply remove the G2 hammer and take a dremel to it until it has the recommended face profile 
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Quoted:
I looked at it again during lunch and took some measurements. I think the receiver has multiple problems. If you look at the second set of pictures, the bolt lug isn't even between the rails. It's resting on the bottom rail but just sliding against the top rail. In other words, not locked in. I also think my measurements back this up: Left rail measurements between upper and lower left rail are .243, .24, and .255. The bolt lug measures .265. It's not going to fit let alone have room to slide. Receiver width from upper rail to upper rail from back to front are .95, .88, .79, and .75. Definitely wider in the back but of course the bolt has basically been prying it apart every time it cycles because it's not in between the rails. This is of course my theory based on my measurements but I'll wait to see what you guys think. The bolt lugs on each side "ride" on top of the lower rails. The bolt stem's snug fit keeps the bolt from rotating past either rail. The bolt I have, the stem measures 10.90mm in diameter and the carrier opening for it measures 11.02mm. 
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Quoted:
I looked at it again during lunch and took some measurements. I think the receiver has multiple problems. If you look at the second set of pictures, the bolt lug isn't even between the rails. It's resting on the bottom rail but just sliding against the top rail. In other words, not locked in. I also think my measurements back this up: Left rail measurements between upper and lower left rail are .243, .24, and .255. The bolt lug measures .265. It's not going to fit let alone have room to slide. Receiver width from upper rail to upper rail from back to front are .95, .88, .79, and .75. Definitely wider in the back but of course the bolt has basically been prying it apart every time it cycles because it's not in between the rails. This is of course my theory based on my measurements but I'll wait to see what you guys think. The bolt lugs for the most part, don't "fit" between the upper and lower rail. They mostly "sit" on top of the lower rail. The upper rails are for your carrier. The carrier holds the bolt down against the top of the lower rails imho. That's why I mentioned how tight did your bolt fit the carrier. I'd measure width of receiver from front to back, using the outside. It should be the same front front to rear. As I had a receiver too tight one time causing the carrier to bind as it went rearward (I pried it a hair wider), it may be a simple fix of taking a rubber mallet to the receiver to bring it back to where the carrier just fits it's rails. Wish there was an AK-smith you could visit, these things can kill you very easy with the pressures involved and heavy parts moving at high speeds. At this point I'm assuming someone didn't know what they were doing and tried to put the carrier and bolt in completely wrong, forcing it, which began the issue you see worsening today. Then again, I may be wrong. |
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Gun was bought used on gunbroker. I used Never dull on the top of the rail and the guides on the bolt carrier. Didn't even rub enough to take any paint off. It did take paint off the hammer where I polished. On the rails, if you look at the second set of pictures, the third picture does show the very rear of the rail slightly bent upwards. It's even shiny where the carrier has been rubbing. Don't know if that's a big deal buts it's the only thing I could find that looks like unusual wear. The left side is bent slightly upwards as well. Again not a lot but you can tell just by looking that they are bent slightly upwards. Any progress? |
| Took it to my friends gun shop this morning and we compared another AK. Only thing we could see different is the bolt did have some slop when it was in the bolt carrier as compared to his. He said it was best just to send it back to Century. Shipping it off Monday. |
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Took it to my friends gun shop this morning and we compared another AK. Only thing we could see different is the bolt did have some slop when it was in the bolt carrier as compared to his. He said it was best just to send it back to Century. Shipping it off Monday. Very good, thanks. |
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I had the same problem and the ejector had to be lowered just bellow the rails there are other things that can do this. If you look at the ejector there is rubbing and some peening on the top of ejector. Upon recoil the bolt is coming back hitting the ejector and twisting then going forward and getting stuck on the feed lips.
http://www.gunco.net/forums/43-ak-biy-forum/82486-bolt-hitting-feed-lip-2.html |
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Update in original post And it was within warranty? That makes no sense. Century has their share of faults, but they typically handle warranty issues satisfactorily. Ive never heard of anyone giving a customer the option of offering to return an item unrepaired or reimbursing them for the wholesale price of the rifle. The former, sure, but never the latter. Bizarre to say the least. |
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And it was within warranty? That makes no sense. Century has their share of faults, but they typically handle warranty issues satisfactorily. Ive never heard of anyone giving a customer the option of offering to return an item unrepaired or reimbursing them for the wholesale price of the rifle. The former, sure, but never the latter. Bizarre to say the least. Quoted:
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Update in original post And it was within warranty? That makes no sense. Century has their share of faults, but they typically handle warranty issues satisfactorily. Ive never heard of anyone giving a customer the option of offering to return an item unrepaired or reimbursing them for the wholesale price of the rifle. The former, sure, but never the latter. Bizarre to say the least. He bought it used on gunbroker. I honestly am surprised Century did anything for him. |
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