PTR 91 Malfunction Diagnosis

[AlaskanScout]

Hello, this is my first post here and my first post on a firearms forum in general and I thank you all in advance for lending your extensive experience to better the shooting community as a whole.

Now a few weeks ago I became the proud owner of a PTR 91 A3S. On my first outing I was having an alarmingly high frequency of failures to fire by light primer strike. I diagnosed this as a failure for the bolt carrier assembly to return fully to battery and on a subsequent range trip where 40 rounds were fired the issue happened only once.

Fast forward to earlier today and the light primer strike problem is no more, however I am having an alarming number of failures to fully extract/eject.

The rifle is fairly clean and moderately lubed, I don't have it as wet as I usually run my guns but neither is it dry.

Does anyone have an idea as to what this could be? Can I fix this problem myself or would I need to send it back to PTR to have it looked at? The rifle has as of now 240 rounds through it, is this to be expected as a side effect of break in?

I thank you all again for your speedy and informative replies and cannot wait to to become a more active member of this forum.

 

[stubbicatt]

Hard to say without watching it in action. But here are my suggestions:

1) Ammo. Some of these are sensitive to tar sealed bulleted ammunition. If the cartridge is not extracting, clean the chamber flutes, and shoot a different brand of ammunition.

2) Low ejector. If the cases are extracting but not ejecting, turn the rifle onto its back so you have a good view up thru the magazine well. The ejector is that doohickey that pivots in the port side of trigger pack, and extends above the line of the top of the trigger pack, fore and aft. It interfaces with the bolt at the front and carrier at the rear. It should ride up into the ejector groove in the bolt and nearly bottom out in the groove. If you pull back on the cocking handle, and observe thru the ejection port and magazine well as the ejector approaches the bolt face, there should be very little clearance between the bottom of the ejector groove and the top of the ejector.

The cause of the low ejector in these rifles is typically a shelf/trigger pack "clip" that has not been properly dimensioned, and typically will require a trip back to the factory. A field expedient repair can involve some cardboard shims under the front of the trigger pack, between the trigger pack and the grip frame, at the front, that sort of pivots the trigger pack upwards at the front while pivoting around the static pivot provided by the selector/safety.

ETA: while an unlikely occurrence, bolt gap, if too small, can prevent operation of the rifle. Check the bolt gap thru the magazine well. Shrinking bolt gap causes can vary, but a cracked trunnion can be one cause, improper barrel pinning another.

Lastly check the bolt roller windows or apertures and the near area around them for cracking. PTR, Inc. had a spate of bad bolts that would crack here. I understand that they have rectified this issue, but it is cheap insurance to buy a GI bolt and locking piece, and if you can find it, a Rheinmetall carrier.

As for lubing, the only area I put oil, or a mixture of heavy grease and oil, on is the two grooves on the bolt carrier, or impressions in the receiver that interface with the two fore/aft grooves in the carrier. A drop of oil on the mainspring shaft at the very front where the spring collar is, and a very light oil on the locking piece, or wedge shaped device that presses out the rollers, is all that is necessary.

HTH.

 

[wally]

2) Low ejector. If the cases are extracting but not ejecting, turn the rifle onto its back so you have a good view up thru the magazine well. The ejector is that doohickey that pivots in the port side of trigger pack, and extends above the line of the top of the trigger pack, fore and aft. It interfaces with the bolt at the front and carrier at the rear. It should ride up into the ejector groove in the bolt and nearly bottom out in the groove. If you pull back on the cocking handle, and observe thru the ejection port and magazine well as the ejector approaches the bolt face, there should be very little clearance between the bottom of the ejector groove and the top of the ejector.

The cause of the low ejector in these rifles is typically a shelf/trigger pack "clip" that has not been properly dimensioned, and typically will require a trip back to the factory. A field expedient repair can involve some cardboard shims under the front of the trigger pack, between the trigger pack and the grip frame, at the front, that sort of pivots the trigger pack upwards at the front while pivoting around the static pivot provided by the selector/safety.

Very well described. It would be the first thing to check, if different ammo is not the solution. My CETME had this issue. I found a C-clip that was a good fit to the axis pin and used it as a spacer to solve the problem as mine was OK up/down but had left/right wobble than made ejection iffy.

 

[AlaskanScout]

I was using ZQI 7.62 from walmart so that very much could have been it. Unfortunately it will be a while before I can actually test these but I appreciate your help and will definitely be checking these items before my next range trip.

It's unfortunate. I've owned several guns before this that have all functioned flawlessly and I was lead to believe that the G3 clones were the same way. Guess that's the price of being on a budget!

 

[M1key]

I would be surprised if ZQI was the problem. However, it wouldn't hurt to try some other ammo..

M

 

[seasmoke]

Also check your extractor. If you can wiggle it with your finger, the spring is toast. A weak spring will cause failure to extract. An easy fix, and a good thing to have a few spares of.
As to the ZQ ammo, I have put many rounds through my PTR and my HK-33 Klone without issue.

 

[Slamfire]

Some background, these rifles function by breaking the friction between case and chamber. Quite literally, the case is popped out of the chamber same as a cork popping out of a champagne bottle. Friction between the case and chamber is bad,



and so are dirty flutes. The flutes go about 2/3rds of the way down the chamber, and so the last 1/3 of the case is the gas seal.



So keep the flutes clean, use clean ammunition. Now my suggestion, next time you fire that ammunition, oil the outsides. See if oily ammunition extracts better, functions better. If you still have failures to eject, do everything that Stubbicat says to do.

And, lube everything in the bolt group, don't run this gun dry. I liberally apply grease to the connecting rod and the rollers.



Lube this well!

 

[mshootnit]

I am dealing with this now. Most ammo would fte at least half the time out of my new rifle. Noticed the ejector was riding low in the slot. Took out the pack, took out the ejector. Vised it up in a small portable vice. Hammered the whole thing on my cement garage step to increase the ejector height. Reassembled. Range test 2 fte out of twenty five with mixed ammo. Getting better.

 

[AlaskanScout]

When I operated the bolt by hand the cases ejected just fine. Also when I noticed the failures all cases were securely held on the bolt face by the extractor. I believe it may have been dirty chamber flutes as all the brass was pretty nasty, I'll give those a look.

Also, if it was the ejector wouldn't I have had more double feeds? I did experience one double feed but that was one in 240, hardly common enough to call a pattern. The very helpful replies here are leading me to believe it is a failure to clean the chamber correctly and a deficiency in lubrication as further thought experiment has deduced that the bolt must be short stroking. Back enough to get the case most of the way out of the chamber but not enough to engage the extractor or strip a new round. If I'm half as well versed in the function of a delayed blowback operated rifle as I think I am that would surely indicate a source of extreme friction in the system somewhere.

I am very appreciative of the replies and advice and am learning alot about a system of function that is honestly mostly absent from the mainstream of the evil black rifle.

 

[stubbicatt]

If the cases are very sooty with distinct lines on them after firing, it seems that the fluting is working as it should. Adam at HKparts.net has a brush designed for these rifles that one runs in and out of the chamber, not rotating it in the chamber, which will drag any offending smuts out of there.

When everything is properly dimensioned, running your rifle dry of lube will not affect function. There is SIGNIFICANT force in the extraction cycle.

Have you verified your bolt gap? It should be between .012" and .020". If it is less than .012" you have identified your issue. + size rollers will rectify the issue until the rifle parts all bed in to one another.

 

[Panzerschwein]

Some background, these rifles function by breaking the friction between case and chamber. Quite literally, the case is popped out of the chamber same as a cork popping out of a champagne bottle. Friction between the case and chamber is bad,



and so are dirty flutes. The flutes go about 2/3rds of the way down the chamber, and so the last 1/3 of the case is the gas seal.



So keep the flutes clean, use clean ammunition. Now my suggestion, next time you fire that ammunition, oil the outsides. See if oily ammunition extracts better, functions better. If you still have failures to eject, do everything that Stubbicat says to do.

And, lube everything in the bolt group, don't run this gun dry. I liberally apply grease to the connecting rod and the rollers.



Lube this well!

I wouldn't do this OP. You do not want carbon buildup in these areas, or the areas where the rollers lock into the receiver. Excess oil will cause this, and is not needed nor desired on these rifles. Also, you should NOT have to oil your ammunition for it to work properly. That's why your chamber is fluted.

Also, ZQI ammunition is good stuff. I've shot hundreds of rounds of it through my PTR-91 GI and it has never cause a single issue. Keep in mind that this is the same ammo that the Turkish military uses, and guess what their service rifle is?

 

[ttarp]

I let my PTR GI go for +-1,000 rounds without cleaning or lube and it never stumbled, has anyone actually had a dirty chamber cause malfunctions or is it just carry over from early PTRs and tar sealed ammo?

I don't think you'll hurt anything by over lubing everything like described, but I'd be very surprised if it helped any at all, and you'll have a very dirty rifle to clean after shooting.

+1 on verifying bolt gap.

 

[Slamfire]

I wouldn't do this OP. You do not want carbon buildup in these areas, or the areas where the rollers lock into the receiver. Excess oil will cause this, and is not needed nor desired on these rifles. Also, you should NOT have to oil your ammunition for it to work properly. That's why your chamber is fluted.

This year I fired 1800 rounds of 45 ACP in Bullseye pistol, most of the rapid fire rounds were oiled. I dripped oil on the rounds in the stack. Very messy but no failures to extract. It is an old saying in Bullseye, "your elbow is the drip point" I did not see any evidence of "carbon buildup". I heavily lube my AR's, and I greased the heck out of my PTR. My Garands/M1a's, I cannot lube as heavily as the AR's or PTR's because the mechanism tosses lube on my glasses. I have never seen carbon buildup, but then, I also clean my firearms before I put them up. Perhaps if I left them dirty and oily the oil would congeal and dry out. Don't know, I keep my weapons clean and well lubricated.

 

[MechAg94]

I have an older PTR-91. I still have some South African surplus that I have saved just for that rifle since it is berdan primed anyway. It is dirty as hell, but I have never had an issue in that rifle. Cleaning can be difficult.

 

[mshootnit]

2 out of 3 ptr rifles bought new by me in the last two years have had cycling issues out of the box and a fourth came out of the box with a rusted bore from test firing with corrosive ammo. Not sure what is up with PTR now. I know my good rifle had a black extractor the others have been silver. Also the ejector on my current rifle was not making contact on the cases when fired, I could see this by looking at them, before and after I fixed it.

 

[mshootnit]

I have not tried the GI model but my current opinion is that if you plan to buy one otherthan the GI, expect there to be cycling issues which will need adressed(meticulous break in will not cure an ejector riding too low in the bolt). On the bright side they are good groupers usually.

 

[Panzerschwein]

I have not tried the GI model but my current opinion is that if you plan to buy one otherthan the GI, expect there to be cycling issues which will need adressed(meticulous break in will not cure an ejector riding too low in the bolt). On the bright side they are good groupers usually.

Why is that?

PTR now uses one and only one chamber design on their rifles. There is no difference between the GI chambers or the chambers on any other .308 caliber PTR rifle currently being made.

 

[Slamfire]

I remembered that the Swiss STG57 is a roller bolt weapon and that I have several of the cleaning kits. In one container is a medium grease that looks like a moly graphite grease. After searching several posts on Swissrifles.com, I am of the opinion that the Swiss grease the rollers and the inside of the bolt. This section from shows the grease kit and cleaning instructions.

http://swissrifles.com/access/index.html

Close-up of grease can.

The text on the can reads
"AUTOMATENFETT GRAISSE ARMES AUT."
The above phrase is a mixture of German and French.
AUTOMATENFETT is German and traslates to Grease for Automatic
GRAISSE ARMES AUT is French and translates to Grease for automatic firearms
Inside the circle on the center of the lid the is an F+ over a W
Which is the proofmark of the Swiss Waffenfabrik Bern​

Thanks to Andreas Beules for translating, and
Thanks to Mark Adkins for IDing the proofmark.

The cleaning procedure for the kit above is as follows:

1. Make the rifle safe. Remove the magazine and bolt.
2. Assemble the cleaning rod and attach the brass brush with a small amount
of the black grease on the tip of the brush - from the chamber end, make 5
passes through the barrel.
3. Remove the brass brush and attach the brass cleaning jag with a 100%
cotton patch (about 5cm x 5cm square). Run patches through the bore until
they come out clean.
4. Using the cleaning rod handle and one rod section, attach the large
chamber brush with a very small amount of grease at the tip. Scrub the
chamber area thoroughly with the brush - about 5 passes should clean the
area.
5. Remove the chamber brush and attach the chamber jag with a (20cm x 20cm
square) cotton patch slid into the slot cut into the jag. Insert this into
the chamber area and wipe thoroughly and repeat until subsequent patches
come out clean.
6. Reassemble the entire rod and handle - attach the nylon brush and
(lightly) coat with the black grease. Run this brush through the bore to
apply the grease to the bore and chamber area.
7. The bolt should be disassembled and all parts wiped clean. It is
preferable to use oil or the light-colored grease on the bolt as opposed to
the black grease. The remainder of the weapon should be wiped clean and
oiled.
8. The magazine should be disassembled and cleaned as it accumulates firing residue.
*****Remember to remove the grease from the bore before firing the weapon*****

I heavily coated the roller bolt of my PTR 91 , inside and out, with Lubriplate 130. I think any decent grease of similar consistency would work well. I do not believe this rifle should be run dry.