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Old 11-16-2016, 07:16 PM   #141
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Quote:
Originally Posted by Rob Ski View Post
Thank you for this info.
Quick question, by any chance, do you know why they keep switching rear trunnions on those NPAPs coming our way?
The fixed stock 5.56 models usually have a buttstock with a slightly different angle or drop than the M70 buttstock. I don't know if the difference is the cut of the wood or the angle in the back of the trunnion. The wood doesn't match the angle of the sheet metal on the back of the receiver.

The semi-auto's that were imported in the 1980's have the fixed stock model with a smaller wooden pistol grip and M82 RPK hand guards. The folding stock model has the M76 pistol and M70 type hand guards. The trunnions are also spot welded. The pictures I've seen of fixed stock M90's also have a different butt drop or angle than the M70.

There are some two rivet trunnions that have an additional rivet through the bottom the receiver, under the pistol grip. These might be M77, M72 or either receiver version of the M70.

The M90 PAP looks like a two rivet trunnion. Does it have two bottom rivets?


http://www.akfiles.com/forums/showthread.php?t=195820

http://www.mycity-military.com/slika...djenje-001.jpg

Some pics above.


http://imageshack.com/a/img853/755/o80nr.jpg

3 rivet M72 trunnion


http://imagizer-cv.imageshack.us/v2/...538/UkePHl.jpg

4 rivet M70 trunnion
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Old 11-16-2016, 07:26 PM   #142
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The M70 gas port is larger than the AKM gas port to compensate for additional gas bleeding from the spindle valve. Is the NPAP gas port AKM size or M70 size?
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Old 11-16-2016, 09:48 PM   #143
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Quote:
Originally Posted by allesennogwat View Post
The M70 gas port is larger than the AKM gas port to compensate for additional gas bleeding from the spindle valve. Is the NPAP gas port AKM size or M70 size?
Thats the million dollar question.

Have an NPAP you can pull the gb on to measure the port size?

My bet is on M70 size.
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Old 11-16-2016, 10:10 PM   #144
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Quote:
Originally Posted by allesennogwat View Post
The M70 gas port is larger than the AKM gas port to compensate for additional gas bleeding from the spindle valve. Is the NPAP gas port AKM size or M70 size?
I think Mel64d may have an answer to this question. I think he disassembled NPAP before and maybe he took measurements...
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Old 11-16-2016, 10:11 PM   #145
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I just measured a pulled PAP barrel, a pulled excellent M70 and a Romy pulled excellent.
All three at .144" +/- .002"
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Old 11-16-2016, 10:18 PM   #146
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Originally Posted by AKBLUE View Post
I just measured a pulled PAP barrel, a pulled excellent M70 and a Romy pulled excellent.
All three at .144" +/- .002"
That would be M70 size, 3.7 mm. The AKM is suppose to be 3.5 mm, but some recent Romanians are smaller. The Chinese may have gone to a larger gas port.

AKBLUE, I remember you had a Yugo armorer's manual that is different from the one I have. Mine doesn't have the M72. Does yours have the M72 gas port checking? I seem to remember the M72 gas port also being larger than most, but smaller than the M70 as would be expected with a longer barrel. I think I measured the M72 around 3.3 mm, but it could be smaller.
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Old 11-16-2016, 10:45 PM   #147
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Quote:
Originally Posted by allesennogwat View Post
That would be M70 size, 3.7 mm. The AKM is suppose to be 3.5 mm, but some recent Romanians are smaller. The Chinese may have gone to a larger gas port.

AKBLUE, I remember you had a Yugo armorer's manual that is different from the one I have. Mine doesn't have the M72. Does yours have the M72 gas port checking? I seem to remember the M72 gas port also being larger than most, but smaller than the M70 as would be expected with a longer barrel. I think I measured the M72 around 3.3 mm, but it could be smaller.
I'll take a look. I never went over it that thoroughly.
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Old 11-16-2016, 11:31 PM   #148
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Bought a NPAP from Atlantic back in July. It has the 3 rivets.
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Old 11-17-2016, 12:13 AM   #149
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Checked my M77 and M90 .... both have the 2 rivet setup in the rear.

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Old 11-17-2016, 01:39 AM   #150
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Even the larger gas port might still be in spec for an AKM as the used range for the M70 is something like 3.7 mm to 4.1 mm. The Chinese enlarged the gas port around 1965 as part as their, "improvement" program.

Defective springs are not uncommon in several industries.

I wonder if the receiver steel is on the thin and / or weak side of specs.

There are also the bolt carrier tails that get pounded out of shape too.

Maybe the springs are to blame.
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Old 11-17-2016, 01:59 AM   #151
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Quote:
Originally Posted by allesennogwat View Post
Even the larger gas port might still be in spec for an AKM as the used range for the M70 is something like 3.7 mm to 4.1 mm. The Chinese enlarged the gas port around 1965 as part as their, "improvement" program.

Defective springs are not uncommon in several industries.

I wonder if the receiver steel is on the thin and / or weak side of specs.

There are also the bolt carrier tails that get pounded out of shape too.

Maybe the springs are to blame.
I'm toying around with a Saiga, NPAP and WASR. The NPAP and WASR have the same strength spring from what I can tell. The NPAP will hang up on the carrier/hammer if I release slowly. It does this with either the NPAP or WASR spring inserted in the NPAP. However, if I use the Saiga spring in the NPAP, I can NOT get it to hang up no matter how hard I try. Funny thing is, the Saiga has many more rounds fired.

Just my personal observation, but I'm leaning towards it being a combination of a weak spring and 2-rivet trunion that caused the cracking. With the 3-rivet trunion, it also connects to the side rail which is also rivited to the receiver for a total of 9 rivets securing the trunion to the receiver. the 2-rivet trunion not only has less but does not connect to a side rail and reaping the benefits of those additional rivets. Due to this, those forces applied to the 2-rivet trunion have lesser places to go so their exerted to the weakest area, that being the area that cracked.
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Old 11-17-2016, 07:57 PM   #152
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Quote:
Originally Posted by tompat View Post

Just my personal observation, but I'm leaning towards it being a combination of a weak spring and 2-rivet trunion that caused the cracking. With the 3-rivet trunion, it also connects to the side rail which is also rivited to the receiver for a total of 9 rivets securing the trunion to the receiver. the 2-rivet trunion not only has less but does not connect to a side rail and reaping the benefits of those additional rivets. Due to this, those forces applied to the 2-rivet trunion have lesser places to go so their exerted to the weakest area, that being the area that cracked.
I tend to agree. As I said before, if I had to put my finger on something to blame, I would roll with weaker than regular recoil spring which may started whole domino effect here...
It would be interesting to see if more 2 rivets npaps will start experiencing similar problems...time will tell.
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Old 11-17-2016, 10:59 PM   #153
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I also noticed that my Saiga and WASR also have only two rivets on each side of trunion. HOWEVER, the big difference here is that their trunions do connect to their perspective side rails! This might be an early indication that Zastava made a poor choice of going with the wrong type of trunion. It's not because they chose a 2-rivet type, but the wrong type that doesn't connect side rail like other manufacturers are using. Their trunion selection probably would be fine if their receiver not had that non-standard secondary dust cover button.
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Old 11-18-2016, 03:07 AM   #154
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Quote:
Originally Posted by TexasDave View Post
Checked my M77 and M90 .... both have the 2 rivet setup in the rear.

-Dave
Will check my M77 when I get home. Curiosity is peaked.

Edit: Yup got two.

Last edited by Bandy; 11-18-2016 at 07:06 PM.
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Old 11-18-2016, 07:50 AM   #155
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m77 and MA in 308 are 2 rivet
85P in .223 is 3 rivet
M90 in .223 is 2 rivet
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Old 11-18-2016, 09:52 AM   #156
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Quote:
Originally Posted by tompat View Post
I also noticed that my Saiga and WASR also have only two rivets on each side of trunion. HOWEVER, the big difference here is that their trunions do connect to their perspective side rails! This might be an early indication that Zastava made a poor choice of going with the wrong type of trunion. It's not because they chose a 2-rivet type, but the wrong type that doesn't connect side rail like other manufacturers are using. Their trunion selection probably would be fine if their receiver not had that non-standard secondary dust cover button.
Two rivet trunnions have been used on Zastava firearms for three decades. Long before at rails. WASR's use two through rivets and no relationship to the PAP type. But also use the same rivets long before any optics rails were used.

No real connection to you statements.
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Old 11-18-2016, 10:54 AM   #157
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Quote:
Originally Posted by allesennogwat View Post
That would be M70 size, 3.7 mm. The AKM is suppose to be 3.5 mm, but some recent Romanians are smaller. The Chinese may have gone to a larger gas port.

AKBLUE, I remember you had a Yugo armorer's manual that is different from the one I have. Mine doesn't have the M72. Does yours have the M72 gas port checking? I seem to remember the M72 gas port also being larger than most, but smaller than the M70 as would be expected with a longer barrel. I think I measured the M72 around 3.3 mm, but it could be smaller.
I did not find anything in the M72 manual. Nothing like the port size details from the M70 manual.

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Old 11-18-2016, 02:48 PM   #158
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Quote:
Originally Posted by AKBLUE View Post
I did not find anything in the M72 manual. Nothing like the port size details from the M70 manual.

Thanks, That page is different from mine. I remember you mentioned some info in it that mine doesn't have. Maybe it is a higher level of repair manual. Does it have any receiver or ejector drawings? Any rivet information or steel information? I doubt that they mention steel like the Soviet ones do though. Headspace and bolt fitting from that one might be interesting. I have that for the M76 but I don't think I do for the M70 for some reason.
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Old 11-18-2016, 02:49 PM   #159
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There is a member here in Serbia that mentioned that Zastava was considering changing the M21 receiver from 1.5mm to 0.9mm. That might still be with an RPK type trunnion though.
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Old 11-18-2016, 06:09 PM   #160
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Quote:
Originally Posted by Rob Ski View Post
I would say that you are correct, M21 has 3 rivets as well.
This whole thing is confusing, my friend just bought brand new NPAP as well and he has 2 rivets in the rear....
His SN is upper 53k. Mine was in lower 53k.
I guess the fact that you didn't prevent your friend from purchasing his NPAP tells us how you really feel about the rifle.
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Old 11-19-2016, 05:15 AM   #161
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I dont want to ask but should i worry about my opap cracking like this in the future?
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Old 11-19-2016, 07:45 AM   #162
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Originally Posted by Dogbite View Post
I guess the fact that you didn't prevent your friend from purchasing his NPAP tells us how you really feel about the rifle.
He panicked before the election. Hillary is responsible for that one! Lol
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Old 11-19-2016, 08:05 AM   #163
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Originally Posted by AKBLUE View Post
I did not find anything in the M72 manual. Nothing like the port size details from the M70 manual.

Do you guys read the manual or just look at the pics? lol
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Old 11-19-2016, 08:40 AM   #164
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Originally Posted by 7.62menace View Post
I dont want to ask but should i worry about my opap cracking like this in the future?
Not with its beefy 1.5mm receiver.
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Old 11-19-2016, 08:48 AM   #165
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Not with its beefy 1.5mm receiver.
Agreed. I haven't heard about anyone with opap complaining about cracked receiver yet. Unless I missed something.
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Old 11-19-2016, 09:28 AM   #166
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Do you guys read the manual or just look at the pics? lol
there's an android app called "goggles". Take a picture of the page, and it will decide it is text and brings up google translations. It ain't great but you won't starve either....
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Old 11-19-2016, 10:20 AM   #167
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If Zastava did not want to alter the design of the placement of the locking mechanism,
but wanted to slightly lower the placement of the rivet just below it at present, then the designers could increase the material thickness at the rear of the receiver and re-design the rear trunion to accomodate that increased strengthening in thickness of steel.
That would probably solve the design flaw pointed out by Nails, which is right on.
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Old 11-19-2016, 11:21 AM   #168
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Quote:
Originally Posted by Disburse-Now View Post
If Zastava did not want to alter the design of the placement of the locking mechanism,
but wanted to slightly lower the placement of the rivet just below it at present, then the designers could increase the material thickness at the rear of the receiver and re-design the rear trunion to accomodate that increased strengthening in thickness of steel.
That would probably solve the design flaw pointed out by Nails, which is right on.
An irregular receiver thickness? I think not. No stamped AK is so designed and not practical. The 1.5mm receiver resolves this of course.
Whether this crack is repeatable is another issue and no design flaw is proven.

The so called "slabside" 1mm fixed stock Zastava AK's were quite uncommon in any case. The underfolder 1mm M70AB1 was seen much more often in imports etc. Replaced for domestic military use by the 1.5mm M70AB2 underfolder.
The fixed stock PAP 1mm is the exception. Some military were shown from Africa in old pictures. It did not have a model number and was referred to by some as the M70B1 first pattern.
Then the 1.5mm M70B1 was adopted., most common in the USA as kit imports or the O-PAP etc.

Evidently Zastava will produce either based on customer spec's.
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Old 11-19-2016, 11:26 AM   #169
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Originally Posted by 1996Beryl View Post
Is it so hard to imagine that Century Arms contracts the NPAP, OPAP, PAP pistols, etc. to be made to fit specific lower quality standards for a lower price point for the USA market?
Like Walmart does to it's sourced companies products it carries.
.......no, it's not hard to imagine, but there's also no evidence to support such speculation.

A member here cited a Zastava employee commenting that they do not produce civilian
market rifles to the same rigorous quality standards as their military rifles. Now we all
don't know if that's factually a true employee or not ,but......ya know it is possible.
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Old 11-19-2016, 11:39 AM   #170
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Customer specs are common when ordering firearms. The Iraq's used Zastava based firearms with mods as did the Africans etc. Whether there is any relationship to customer request/specs and the cracks on the test N-PAP is kind of a nebulous connection. No real evidence either way?
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Old 11-19-2016, 05:28 PM   #171
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Premature bolt wear? Is that a new allegation?
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Old 11-19-2016, 05:35 PM   #172
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Quote:
Originally Posted by 1996Beryl View Post
Honestly between Robski's negative history with NPAP's, weak receiver bending, Robski and multiple others talking to someone linked to Zastava and them laughing about the quality, mad forum foreign guys adamant to our "PAP"'s, Battlefield Las Vegas using full auto NPAP's and having the trunnions crack prematurely, premature bolt wear, pins walking out, and all the other issues just turns me off to these rifles. Never heard of such bullshit occurring with Norinco and Polytech AKMs, Finnish Valmet, etc. around for several decades of shooting. Hmm..speculation is a marvelous thing.
Look, to be perfectly fair, we have no proof that Serbian guys talking about Zastava dropping ball on US exports quality, really are from Serbia. Anyone can make an account on Facebook or youtube and say that they are from Serbia.
Now, that being said, based on my experiences with npaps, I would never buy them as my only AK to have.
I would take wasr, saiga, vepr and arsenal long before grabbing npap.
I would grab well made kit AK before buying npap.
But that's my personal opinion only.
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Old 11-19-2016, 05:39 PM   #173
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Pins walking out would be a result of a cheap Century paper clip wouldnt it?
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Old 11-19-2016, 06:07 PM   #174
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Some very minor issues in the scheme of things. Like the new WASR non durable furniture etc
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Old 11-19-2016, 06:35 PM   #175
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All AKs are put together by low wage workers. It's all about luck when buying an AK. No certain brand can guarantee 100% reliability. If your AK has gone thru 2,000 rounds without malfunctions, then it's safe to rely on that AK.
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