What is going on with my PTR91K???

[Southern Raider]

Keep in mind as you read this that until a year ago, I owned a real German HK91. I'm not a complete stranger to the platform.

I took my new to me PTR91K (early AW06xx serial number) out to the desert yesterday. This thing cycles quite hard. Even with a port buffer, I was collecting brass over 20 yards from my firing position. My HK never did this. Is there something going on with these early guns? My bolt gap is 0.016".

Has anyone done anything to tame the carrier velocity? I'm all for vigorous ejection, but let's keep some perspective. I looked at using PSG1/MSG90 locking pieces, but they don't fit. I suspect I could add oversize rollers to reduce the energy absorbed.

This model has a collapsible stock which I've never seen or shot before. While most people have objections with the convex rear, I found it just fine. However, when I dismantled the buffer, I found it fully packed in grease. I suspect this is part of the reason the recoil seems so brutal, as the buffer can't compress when full with other substances.

Anyone else have any ideas on what to check? Unless a carrier bounce at the rear of stroke is punching the brass forward, I have no explanation for how far this thing is throwing brass.

 

[stubbicatt]

The bolt gap is right on the money.

These rifles tend to throw the brass pretty far, but 20 yards seems about right as far as mine does, with port buffer installed. Maybe not quite that far, but at about that distance. Some will land closer, but I can't remember many outside of 25 yards away.

How fresh is the mainspring?

I would not mess with the rollers, as to go up one step will put you outside the range of acceptable bolt gap if you measured the present gap correctly.

The affects of the stock buffer on ejection are nil, as the cartridge has been successfully ejected earlier in the bolt cycle than impact with the buffer. Do remove any grease and such from the buffer to improve its performance, and even then the perceived recoil from that arrangement will be noticeably more severe than recoil with a standard A2 stock buffer, or a heavy buffer. Oh... and the collapsible stock buffers will wear out over time, even if I can't tell you how to determine wear.

The only other possible remedy I can think of for the ejection complaint is that perhaps a change in the ejector, which are inexpensive, or perhaps grinding the ejector face so that it has a little bit more of a downwards bevel than they come with stock, might lower the trajectory some, and thus the distance the empties fly.

 

[Southern Raider]

While I don't think the rifle had been fired much at all, the recoil spring is probably surplus. It doesn't seem worn, but I suppose I could try another.

I just don't think that 20 yards of ejection is anywhere near normal and certainly wasn't on the HK I had. It just gives the impression of excessive carrier velocity, and there's nowhere to install an adjustable gas valve.

The affects of the stock buffer on ejection are nil, as the cartridge has been successfully ejected earlier in the bolt cycle than impact with the buffer.

Under normal operation, I would totally agree. However, when rifles cycle hard, the extractor isn't always doing its job in the proper manner. For all I know, it's not fully controlling the ejected case and the case is being struck on the return stroke. All I know is that I can see the fired brass at the upper edge of my peripheral vision when I fire.

 

[hankdatank1362]

20-25 YARDS?!?!?!?

Not feet?

Wow. That's nuts.

 

[stubbicatt]

Well, if you think that something is wrong with the rifle, maybe it is. PTR91, Inc. are great people to deal with. Maybe give them a call and tell them what you are experiencing.

I keep trying to remember how far mine throws brass, and 25 feet seems about right, maybe a little more. I had a misfire in my brain when I glossed over the 20 YARD measurement. Even so, I'm sure I've found some empties about that far away sometimes.

Hope you get an answer you like eventually.

Ooooh! I know! Double check the bolt lock lever. It is that little lever in the bolt carrier that snaps over the bolt head when the action is in battery. Perhaps that piece is worn? I'm not sure exactly what it looks like when worn, but I know that when I changed my PTR bolt carrier for a Rheinmetall carrier, the brass landed a little closer to the firing position. Something I hadn't remembered the first go 'round on this post. Brand new replacements are only like $5 or so.

 

[Southern Raider]

Yes, yards! Most people seem to be reporting 20-25 feet and that is about what my HK did.

The locking lever is actually quite stiff on this and more so than I remember on my HK. I can check the geometry of the piece against a spare carrier I have. Good point.

I certainly will send it back to PTR if the need arises. I'm just trying to check the easy stuff.

 

[Slamfire]

My PTR 91 ejects brass about 20 yards, not feet, without a port buffer.

That brass just hums out of there.

This rifle is not gas operated. Basically it is a retarded blowback. Having a more powerful recoil spring will do a little, like a couple of percentage, but there is not much you can do to slow the bolt carrier.

I did buy one a plastic recoil pad that replace the buffer. The slap from the recoiling bolt was lessened.

 

[MarcusWendt]

OY!!! 20 to 25 yds? That's got to piss off a range neighbor. I just picked up a PTR-91. It, and rifles for the most part are pretty new to me. It's been 20 some odd years since I had an M-16.

What is a port buffer?

I bought this as I felt time for good rifle purchases was running out. I'd like to upgrade it a little if possible.

 

[HankC]

delete. double post.

 

[HankC]

"Double check the bolt lock lever."

+1. Check the locking lever and spring. If worn or broke, bolt gap will open up early and allow rollers to be pushed back in bolt head too early and reduce the delay effect.

 

[stubbicatt]

If you have a spare carrier, just substitute the spare to see if it does any different.

I'm still thinking perhaps the angle of the ejector could be modified to deflect brass downwards a bit.

Marcus: The port buffer is a stamped metal piece that snaps over the outside of the receiver, and positions a rubber buffer outside the rear of the port. The rubber buffer both deflects brass downwards and helps preserve the brass from that "smile" like hickey-crease that the ejection port tends to leave midway down the walls of the spent casing. Robert RTG parts online sell them for $50 or so. It is a great addition to your rifle if you wish to reload the brass

'Course you gotta find them first, and if they are being flung 25 yards away in the tall grass, that might be an issue.

 

[Martyk]

Brass Ejection & damage

Greetings - I just had my brand new PTR-91 Perimeter Rifle to the range for the first time yesterday. The ejection is VERY aggressive.. 40-60 FEET, but its a forward eject. The brass is not hitting the guy 6 ports down, but it landing 20 feet in front of him.

I've been reading about brass damage and the port buffer. I want to reload and was disappointed to see how beat up the brass is. I spent some time taking everything apart and trying to figure out what was happening by studying the tell tale signs on the cases. The damage that is most troubling is a dent at the bottom of the neck taper. I could not see how this could happen on ejection. But it looks like it is happening when the round gets stripped out of the magazine.

Anyone else see this??? I will try to post some pics of the damaged brass to compare it to what other people are seeing. I love the Rifle but if I can resolve the brass damage issue it would put it over the top!!

 

[Evil Monkey]

The G3 design ejects shrapnel.

 

[sharkhunter2018]

Martyk - I don't own one of these although I wish I did but...butchered brass seems to be the norm with the PTR and other similar rifles. One of my buddies test fired a CETME awhile back and it just destroyed the mouths and necks.

I still want one though.

 

[MGshaggy]

The damage that is most troubling is a dent at the bottom of the neck taper.

Sounds like the normal denting of brass you get with a G3/HK91 clone - should be better with a port buffer.

 

[TexasRifleman]

Yeah I had the same trouble til I put on a port buffer and that tamed it tremendously.

Hate to ask, and don't mean any offense, but are you sure the port buffer is on right? Is the brass hitting it properly at ejection?

Not saying there isn't something else wrong with the thing but as you say, not having any gas adjustment leaves the list of causes for this pretty short.

 

[woodybrighton]

G3's tend to eject with a lot of force.
if you wind down a fals gas to 1 you can get the same sort of effect

 

[Martyk]

Reply to Texasrifleman

Hey Tex - no offense at all in your question. I don't have the port buffer yet. I shot my Rifle for the first time on Sunday and learned about the PB by reading posts here.

However, in investigating the possible causes of the dents by playing with and studying the action (last night) it sure looked like the neck dent was being caused on the way into the chamber when the round is getting stripped out of the mag. It's just the way I saw the marks on the case line up.

Anyways...I have a little ore evaluation to do and I will definitely invest in a Port Buffer because I fully intend to reload for the purpose of getting as much accuracy as I can out of the Bad Boy.. not to mention it financially advantageous and Fun!

 

[euclid]

Another PTR-91 owner here. My rifle spits out brass > 20 yards also. I've read that it's fairly common.

cheers

 

[Southern Raider]

I think I have everything figured out. The previous owner had the port buffer notched in the top rear (looks milled) to not interfere with the scope mount. I'm guessing the end result is less rigid and the sides act like springs when hit by ejecting brass. The rifle actually throws brass half as far without the buffer installed.

Also, cleaning out the grease from the recoil buffer makes a big difference in how it operates!

 

[stubbicatt]

However, in investigating the possible causes of the dents by playing with and studying the action (last night) it sure looked like the neck dent was being caused on the way into the chamber when the round is getting stripped out of the mag. It's just the way I saw the marks on the case line up.

I dunno MartyK. If the necks were being squashed on the way into the chamber, wouldn't the presence of the bullet in the case neck sort of make that impossible?

Without a port buffer in my rifle, the case necks strike on the front leg of the clamp on scope mount and get a hickey in that fashion. With the port buffer, I am happy to report no denting at all in the brass. It is dirty and ugly, and cast pretty darned far away, but it is not dented at all. Suitable for reloading!

Either way, this is my favorite rifle.

The previous owner had the port buffer notched in the top rear (looks milled) to not interfere with the scope mount. I'm guessing the end result is less rigid and the sides act like springs when hit by ejecting brass.

I haven't seen your buffer, Southern Raider, but mine has a protrusion of sorts which actually clamps over the rear of the ejection port, and into the receiver window, keeping it from shifting backwards upon impact. It is quite rigid due to this feature. That yours was notched for the scope base shouldn't affect that, if the little protrusion is properly affixed over the rear of the ejection port.

BTW, is yours set up for the claw mount or does it have the rail welded to the top of the receiver? Mine is an old JLD rifle, and uses a claw scope mount, but the buffer didn't require any notching or machining to work perfectly with the scope. If you have a digicam I sure would be interested in seeing what you have described.

To Original Contributor, I just thought of something. Yours is the 16" barreled version, I think I remember you saying. I wonder if PTR91, Inc. installed a different locking piece in these rifles over what they did in the 18" barreled versions? G3 Locking pieces are cheap, ranging in price from as low as $12 and up to $24 or so online. You might compare locking pieces with the G3 and the one in your rifle and see whether they have different tapers. Or just try the G3 locking piece in your rifle. It might have the effect of slowing the unlocking of the bolt, which might decrease the distance the brass is being tossed.

Stubb out.