H&K91/G3 head space or bad ammo?

James Kain · September 1, 2008, 10:05 AM

I picked up a knock off of the H&K91/G3 and every time I take it out shooting I can get about 3 shots before it stops reloading. The shells are getting spit out all blackened and I have to beat the charging handle to pull the shell out. I have been shooting surplus ammo most likely from South Africa and VERY HOT! But if that is not the case, could it be head space or I have no idea!?! The only smithy I know of in the area dose not work on barrels or triggers! He dose beautiful work tho! I do know of someone else that works automatics but I m not sure if he can help me. I wanted to pop in here and ask you guys before I wasted so much gas running around. Besides the info I find here from the people with the same love as my self in priceless!

ocharry · September 1, 2008, 12:47 PM

have you checked the bolt gap???

if you turn the rifle upside down and look into the magazine well,,you will see the bolt head and the bolt carrier,,,there should be a gap between the two parts

.004-.018 is the range for the gap,,,,AND the needs to be a gap of the same size between the cocking lever plunger and the end of the bolt carrier,,,if not it could be holding the bolt carrier away from the bolt head,,,giving a false reading or a bolt gap that is not really there

check it out and get back with the results

ocharry

Harry Bonar · September 1, 2008, 02:53 PM

Sir;
Usually blackened cases are caused by the case not sealing the powder gases. For this to be headspace it would need to be terribly loose. Do you have a fluted chamber - but fluted chambers do not produce sooted cases, simply visible fluting on the cases, and they can be resized.
I'm thinking it's your ammo. Buy a box of Federal or Winchester and try it - but first clean out that chamber and bore spotlessly, get a smith to run a headspace guage in it ans make sure your headspace is O.K.

Thet's all I know to tell you.
Harry B.

hockeysew · September 2, 2008, 01:00 PM

H & K and most clones with a fluted chamber will blacken the brass to a degree. The fluting serves 2 purposes.
1- Tolerance of combat conditions/ammo.
2- The combustion gases escaping to the chamber help to "float" the brass somewhat, aiding in extraction.
One of the great advantages to the the HK recoil operated system is it's tolerance to varying ammunitions. They will eat anything. I have actually loaded 4 different types of ammo in the same magazine and my JLD ran without a hitch. Try that with a FAL without adjusting the gas system.

I am curious which brand rifle it is. HK, JLD and Vector are all very reliable and some of the JLD's build quality exceeds HK's.
Now if you have a Century CETME or the like, that is a horse of a different color.
You mention that after 3 or so rounds it stops RELOADING. This is critical as it tells me it has nothing to do with the cases being extracted.
You have a feed related issue.
The first thing I would check would be your magazines. If it is a CETME and you are trying to use HK style mags well, some will work others wont.
Try changing mags. If it is a CETME they are really picky on mags.
If you are using SA ammo , there is nothing wrong with that ammo and all of my MBR's run it reliably.
If you are running a "Dirty" ammo like Wolf or some of the Serbian surplus it will leave cases black.

HK and the clones will leave the chamber area quite dirty due to the fluting. Dont be alarmed and the best way to clean it is with aerosol carb cleaner. (Keep it away from the plastic)

If it is a Century gun and you are checking the bolt gap, pay attention to the back of the bolt. does it appear to have been ground? This was Century's way of changing the bolt gap, instead of changing to a different size roller as HK designed it.
Century and their "Angery Beavers"

It should be fixable though so dont despair.
Try changing mags first.

ocharry · September 2, 2008, 01:08 PM

Mr. Bonar is right about the ammo

IIRC some of the NATO stuff(and it may have been south african) used tar to seal the rounds and i do remember some of the guys on another forum taking about having trouble with it

your chamber is fluted on that rifle and you should be able to see it on a fired and extracted casing

usually the chamber pressure will clean the flutes once the bolt starts to open but the tar really clogs things up

give the rifle a good cleaning and especially the chamber and try some other ammo as harry has suggested,,,,

these rifles are designed for 7.62x51 and commercial 308 will work but the cases are thinner walled and it may cause trouble too,,,,try another brand or manufacturer of NATO ammo

and if this is a century rifle you really should check the bolt gap

my .02

ocharry

James K · September 2, 2008, 02:58 PM

Some of that SA brass is too soft so it doesn't fully contract for expansion. I had trouble with that ammo in an FAL and had to polish the chamber (not an option in your case). I would not be concerned unless it gives problems with good ammo.

Jim

James Kain · September 3, 2008, 12:36 AM

Hey thanks! All the info is fantastic! And yes I be leave it is SA ammo! I thought they made good ammo. I guess not and that's why you can find it cheap everywhere! Or used to find it everywhere.
Now I know better then how I phrased the issue with my issue. (girlfriends can really nag when they wanna go shopping!) I was a 45B in the army. (Small arms and tow repair) Really just a parts replacer and trouble shooter. Now the issue with my weapon is that when I fire it starts to gum up quick! So I do think it maybe a tar issue. The issue is after firing the first few rounds it starts to stick. Then fallowing I really have to jam the charging handle to reload the next round. As it sits now I have to really jam the charging handle to move it. So it must really be the tar.
As a side note: A friend with a brake action was using some of the ammo. He complained the the ammo really was hot and kicked hard. Then when he opened it, the shell was stuck. We tryied to eject it a few more times and finly have to use a cleaning rod to push it out!

Tar it is I be leave! I will let you know after tomarrow when I hit up the range and run some hand made 130GR BT-SP's thru it.
WISH ME LUCK
Thank you all for your time. If you have any pointers and or tips, I m open.

ocharry · September 3, 2008, 12:32 PM

james,,,looking at your pix there i noticed that the scope rail looks like one of those that pinches the top part of the receiver

i have read where guys have complained about that type of scope mount,,,if it is to tight on the receiver it will in fact pinch the top of the receiver and cause the bolt carrier to rub the inside of the receiver slowing the cycle of the rifle and causing feeding issues

since you don't have a scope on it i would take it off and give the rifle another try with out it

just a thought,,, you know a picture is worth a thousand words

ocharry

James Kain · September 3, 2008, 12:37 PM

I know what you are talking about with the mount. I loosened it and had no problems running it with that. I do think it is the ammo problem. But I cant know untill I run dif ammo in it

**44 AMP** · September 12, 2008, 08:57 PM

And my experience was that, for a battle rifle, the are somewhat sensitive to the ammo used.

Quote:

2- The combustion gases escaping to the chamber help to "float" the brass somewhat, aiding in extraction.

The HK 91 is probably best described as a delayed (or retarded) blowback. It is often called a "roller locked" action, but in reality it does not actually "lock" in the same sense as other rifles. It is the combination of the roller lock and the fluted chamber that keeps the bolt closed until the pressure has dropped. The fluted chamber is not for debris clearance, or to aid extraction, it is so that the case "sticks" in the chamber longer, so that the pressure will drop before the bolt extracts it. Cases come out dirty, and fluted, and very hot. The the residual gas venting down the flutes does aid in extraction, literally blowing the case out of the chamber, which, because there is no camming action from the bolt head is probably a needed thing. But the main purpose of the fluted chamber is to retain a grip on the case longer than what happens in a non fluted chamber.

For this to work correctly, the case must be of the "proper" hardness. Too soft or too hard and it will not work right. This doesn't matter nearly as much in a rifle like the FAL or the M1A, but in an HK (or clone) it does. German made ammo works excellent. US GI ammo is often too "soft", and can give trouble, as the "soft" brass grips the fluted chamber too well and does not release at the proper time for best functioning. When the HKs first came to the US, lots of guys found them to be jamm-o-matics when using USGI surplus ammo. A quick field fix for this is a light shot of oil to the loaded magazine. The oil reduces the grip of the brass in the chamber and the rifles worked. However, this fix is only for use just before firing, as leaving the ammo oiled in the mag is not a good idea, as oil will kill primers. GI ammo should be proof against this, because it is sealed, but sometimes it is less than perfect. And the oiled ammo picks up dust and grit if exposed to the environment, which is not a good thing to put into your chamber.

I can't say if the South african ammo is any good or not, I have not used any, sorry. Clean your gun, try some other ammo, and see how it behaves.

The scope mount was mentioned, and might be a problem. Take your rifle down, and with the spring out work the bolt back and forth (after cleaning), if any drag is felt, remove the scope mount and try again. IF it still binds, you might need the services of a professional to see if the reciever has been damaged.

Good luck, and let us know how it goes.

James Kain · December 5, 2008, 04:51 PM

Ok, I know its been sometime but crap happens at the speed of life.

My 91 is still not working right. I took hand loaded ammo out today to give her a try. I had 2 types of ammo to try. 1 was 180gr BT-SP and the other 130gr SP's. If it was getting plugged from the crap in the surplus ammo it may have started blowing it out. I got about 3 or 4 reloads that fired. The rest either didnt reload or didnt slide all the way in to battery. So you would hear a click but no bang. The ammo was fed back thur after inspection and not but a small bump on the primer. The firing pin stopped just on the outside of the primer. So I m not sure what happend. I cleaned the hell out of it. I put a a little lube on moving parts.

The shells came out blackend still but not as bad. This time they started comming out with a funnly star type folwing on the moth/rim/neck of the case. The charging handle is rather hard to charge. I m wondering if the spring is to stiff. If that be the case how would I lower that?

rezman · December 5, 2008, 06:16 PM

Hello James,

The century made rifles, (doesn't matter if its a G3 or Cetme, both parts kits built up on an out of spec receiver), can be a real crapshoot when it comes to quality. May I suggest a vist to the following website to familiarize yourself with the HK delayed blowback system. Best information on the interweb I have found.

http://www.militaryfirearm.com/Forum...read.php?t=638

Hope this helps.

James Kain · December 5, 2008, 07:26 PM

If I have time this weekend I m going to tare it down and see if there is any issues with the bolt or bolt carrier. Something tells me that there maybe a lube issue on the carrier. Of coerce I m just hoping here.....Most my knowledge has to do with standard issue us army fire arms. became my job was to make the armors look like a joke I mean if they couldn't replace it, it came to me.

jdowney · December 20, 2008, 11:14 PM

Definitely check out militaryfirearm.com, they've got a lot of regulars who're experts on these rifles and even build them out of demilled parts kits.

James Kain · December 21, 2008, 12:36 AM

Thanks, but the thing was too much of a head ake, and I need to pay off a smithy on some costom work I m getting done to a swedish mauser. So I m going to be selling it soon. I m not sure where or when but I would love to get the biggest bang for my buck.

September 1, 2008, 10:05 AM	#1
James Kain Member Join Date: July 17, 2008 Location: Maine Posts: 83	H&K91/G3 head space or bad ammo? I picked up a knock off of the H&K91/G3 and every time I take it out shooting I can get about 3 shots before it stops reloading. The shells are getting spit out all blackened and I have to beat the charging handle to pull the shell out. I have been shooting surplus ammo most likely from South Africa and VERY HOT! But if that is not the case, could it be head space or I have no idea!?! The only smithy I know of in the area dose not work on barrels or triggers! He dose beautiful work tho! I do know of someone else that works automatics but I m not sure if he can help me. I wanted to pop in here and ask you guys before I wasted so much gas running around. Besides the info I find here from the people with the same love as my self in priceless!

September 1, 2008, 12:47 PM	#2
ocharry Senior Member Join Date: October 20, 2006 Posts: 766	have you checked the bolt gap??? if you turn the rifle upside down and look into the magazine well,,you will see the bolt head and the bolt carrier,,,there should be a gap between the two parts .004-.018 is the range for the gap,,,,AND the needs to be a gap of the same size between the cocking lever plunger and the end of the bolt carrier,,,if not it could be holding the bolt carrier away from the bolt head,,,giving a false reading or a bolt gap that is not really there check it out and get back with the results ocharry __________________ The felon does not fear the police, and he fears neither judge nor jury. Therefore what he must be taught to fear is his victim." - Lt. Col. Jeff Cooper, USMC

September 1, 2008, 02:53 PM	#3
Harry Bonar Senior Member Join Date: December 5, 2004 Location: In the Vincent, Ohio general area. Posts: 1,804	black cases Sir; Usually blackened cases are caused by the case not sealing the powder gases. For this to be headspace it would need to be terribly loose. Do you have a fluted chamber - but fluted chambers do not produce sooted cases, simply visible fluting on the cases, and they can be resized. I'm thinking it's your ammo. Buy a box of Federal or Winchester and try it - but first clean out that chamber and bore spotlessly, get a smith to run a headspace guage in it ans make sure your headspace is O.K. Thet's all I know to tell you. Harry B.

September 2, 2008, 01:08 PM	#5
ocharry Senior Member Join Date: October 20, 2006 Posts: 766	Mr. Bonar is right about the ammo IIRC some of the NATO stuff(and it may have been south african) used tar to seal the rounds and i do remember some of the guys on another forum taking about having trouble with it your chamber is fluted on that rifle and you should be able to see it on a fired and extracted casing usually the chamber pressure will clean the flutes once the bolt starts to open but the tar really clogs things up give the rifle a good cleaning and especially the chamber and try some other ammo as harry has suggested,,,, these rifles are designed for 7.62x51 and commercial 308 will work but the cases are thinner walled and it may cause trouble too,,,,try another brand or manufacturer of NATO ammo and if this is a century rifle you really should check the bolt gap my .02 ocharry __________________ The felon does not fear the police, and he fears neither judge nor jury. Therefore what he must be taught to fear is his victim." - Lt. Col. Jeff Cooper, USMC

September 3, 2008, 12:32 PM	#8
ocharry Senior Member Join Date: October 20, 2006 Posts: 766	james,,,looking at your pix there i noticed that the scope rail looks like one of those that pinches the top part of the receiver i have read where guys have complained about that type of scope mount,,,if it is to tight on the receiver it will in fact pinch the top of the receiver and cause the bolt carrier to rub the inside of the receiver slowing the cycle of the rifle and causing feeding issues since you don't have a scope on it i would take it off and give the rifle another try with out it just a thought,,, you know a picture is worth a thousand words ocharry __________________ The felon does not fear the police, and he fears neither judge nor jury. Therefore what he must be taught to fear is his victim." - Lt. Col. Jeff Cooper, USMC

September 2, 2008, 01:00 PM	#4
hockeysew Member Join Date: August 21, 2008 Posts: 91	H & K and most clones with a fluted chamber will blacken the brass to a degree. The fluting serves 2 purposes. 1- Tolerance of combat conditions/ammo. 2- The combustion gases escaping to the chamber help to "float" the brass somewhat, aiding in extraction. One of the great advantages to the the HK recoil operated system is it's tolerance to varying ammunitions. They will eat anything. I have actually loaded 4 different types of ammo in the same magazine and my JLD ran without a hitch. Try that with a FAL without adjusting the gas system. I am curious which brand rifle it is. HK, JLD and Vector are all very reliable and some of the JLD's build quality exceeds HK's. Now if you have a Century CETME or the like, that is a horse of a different color. You mention that after 3 or so rounds it stops RELOADING. This is critical as it tells me it has nothing to do with the cases being extracted. You have a feed related issue. The first thing I would check would be your magazines. If it is a CETME and you are trying to use HK style mags well, some will work others wont. Try changing mags. If it is a CETME they are really picky on mags. If you are using SA ammo , there is nothing wrong with that ammo and all of my MBR's run it reliably. If you are running a "Dirty" ammo like Wolf or some of the Serbian surplus it will leave cases black. HK and the clones will leave the chamber area quite dirty due to the fluting. Dont be alarmed and the best way to clean it is with aerosol carb cleaner. (Keep it away from the plastic) If it is a Century gun and you are checking the bolt gap, pay attention to the back of the bolt. does it appear to have been ground? This was Century's way of changing the bolt gap, instead of changing to a different size roller as HK designed it. Century and their "Angery Beavers" It should be fixable though so dont despair. Try changing mags first.

September 2, 2008, 02:58 PM	#6
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	Some of that SA brass is too soft so it doesn't fully contract for expansion. I had trouble with that ammo in an FAL and had to polish the chamber (not an option in your case). I would not be concerned unless it gives problems with good ammo. Jim

September 3, 2008, 12:37 PM	#9
James Kain Member Join Date: July 17, 2008 Location: Maine Posts: 83	Scope Rail I know what you are talking about with the mount. I loosened it and had no problems running it with that. I do think it is the ammo problem. But I cant know untill I run dif ammo in it

December 5, 2008, 04:51 PM	#11
James Kain Member Join Date: July 17, 2008 Location: Maine Posts: 83	Still issues Ok, I know its been sometime but crap happens at the speed of life. My 91 is still not working right. I took hand loaded ammo out today to give her a try. I had 2 types of ammo to try. 1 was 180gr BT-SP and the other 130gr SP's. If it was getting plugged from the crap in the surplus ammo it may have started blowing it out. I got about 3 or 4 reloads that fired. The rest either didnt reload or didnt slide all the way in to battery. So you would hear a click but no bang. The ammo was fed back thur after inspection and not but a small bump on the primer. The firing pin stopped just on the outside of the primer. So I m not sure what happend. I cleaned the hell out of it. I put a a little lube on moving parts. The shells came out blackend still but not as bad. This time they started comming out with a funnly star type folwing on the moth/rim/neck of the case. The charging handle is rather hard to charge. I m wondering if the spring is to stiff. If that be the case how would I lower that?

December 5, 2008, 06:16 PM	#12
rezman Member Join Date: January 18, 2000 Posts: 60	Hello James, The century made rifles, (doesn't matter if its a G3 or Cetme, both parts kits built up on an out of spec receiver), can be a real crapshoot when it comes to quality. May I suggest a vist to the following website to familiarize yourself with the HK delayed blowback system. Best information on the interweb I have found. http://www.militaryfirearm.com/Forum...read.php?t=638 Hope this helps.

December 5, 2008, 07:26 PM	#13
James Kain Member Join Date: July 17, 2008 Location: Maine Posts: 83	Thanks If I have time this weekend I m going to tare it down and see if there is any issues with the bolt or bolt carrier. Something tells me that there maybe a lube issue on the carrier. Of coerce I m just hoping here.....Most my knowledge has to do with standard issue us army fire arms. became my job was to make the armors look like a joke I mean if they couldn't replace it, it came to me.

December 20, 2008, 11:14 PM	#14
jdowney Junior Member Join Date: September 21, 2008 Location: New Mexico Posts: 11	Definitely check out militaryfirearm.com, they've got a lot of regulars who're experts on these rifles and even build them out of demilled parts kits.

December 21, 2008, 12:36 AM	#15
James Kain Member Join Date: July 17, 2008 Location: Maine Posts: 83	Thanks, but the thing was too much of a head ake, and I need to pay off a smithy on some costom work I m getting done to a swedish mauser. So I m going to be selling it soon. I m not sure where or when but I would love to get the biggest bang for my buck.