Hk-91 bolt woes, need advice

[Old Guard]

okay took out the Hk91 and shot off a clip..I noticed the cases were red hot and all smoked up, dense carbon around the base..They normally are striped and thrown a long away from the rifle...okay thought about it a while and decided it was firing with out the bolt locking..Turned it over to check the headspace,,,Normal of .005..Cycle the rifle by hand and it looks to be about .60.._ammit.what happened? Pulled it back and let it slam it went into battery, and about .005 again..So several cycles and it changes again to unlocked...I had this bolt out to clean it and you who have them know it is so -am hard to put back and get into rifle..I did not dream it could fire with such a gap.. What did I do wrong?, Can the wedge be put in upside down? I am going to test it again this weekend..if it does it anymore then, it is coming apart..I have not replaced any parts, It was filthy and i cleaned it like several times before.I am asking here as I lost my password for hk pro forum.. Little help here if you have ever noticed this flaw..Thx.OG.

[timshufflin]

You are saying that your headspace was .005" from go when you measured it and when you cycle the rifle by hand it looked .60"? I am not familiar with your rifle but this sounds crazy if I have this right.

[TommyD11730]

Considering the force it takes to rotate the bolt head onto the bolt carrier I can't dream of one ever coming apart. Could the compression spring on the locking lever be @ fault?

I wish I read this before I just cleaned mine... I'm trying to wonder is it even mechanically possible for the bolt head to rotate in the gun?

Rollers intact?

When I reassemble mine I put the bolt carrier in backwards momentarily to retract the rollers, then it goes together like a glove.

[Eli]

Sounds like a roller issue, but I'm no expert.

Eli

[shortround]

Bolt gap on the HK's are checked with the hammer down on an empty chamber. Let the bolt carrier fly home after checking to make sure it's empty. Then pull the trigger while pointing the rifle in a safe direction. The gap between the carrier and the bolt head should be at least .010" and less than .018" (.25 to .45mm). If your normal is .005", your gap is too tight. Wrong bolt gap can lead to early unlocking and excessive recoil. If your rifle was firing without your bolt "locking", it would be very unpleasantly obvious.

The amount of marking on the case can vary with the cartridge make. If this is a factory rifle, I'd be very surprised at the bolt rollers being worn unless you have a great deal of rounds through it. My '91 from the late 80's has in excess of 8k rounds through it and still has a very acceptable bolt gap.

[Old Guard]

Bolt gap on the HK's are checked with the hammer down on an empty chamber. Let the bolt carrier fly home after checking to make sure it's empty. Then pull the trigger while pointing the rifle in a safe direction. The gap between the carrier and the bolt head should be at least .010" and less than .018" (.25 to .45mm). If your normal is .005", your gap is too tight. Wrong bolt gap can lead to early unlocking and excessive recoil. If your rifle was firing without your bolt "locking", it would be very unpleasantly obvious.

The amount of marking on the case can vary with the cartridge make. If this is a factory rifle, I'd be very surprised at the bolt rollers being worn unless you have a great deal of rounds through it. My '91 from the late 80's has in excess of 8k rounds through it and still has a very acceptable bolt gap.

Yes, but the carrier is not going back to battery each time..The bolt closes againest the barrel..The bolt carrier should close to the rear of it..The wedge in the bolt force locks the bearings into the barrel..I understand this was a german MG setup in WW2..I never thought the rilfe would fire if the boltcarrier was not in position..It stopped at about a 1/8 th inch yesterday..If I let the bolt slam, it will go into ready or battery..If it closes too slow it is not properly locked..The gap looks good like you say, with the hammer down or fired position..The wedge key and the bearings look to be in good shape..The barrel looks good too..I pulled the bolt and carrier out and tryed to lock it together in a different position.I could not find my face shield yesterday, or I would have tryed it out..To do that I am Guessing I need to check the gap with the mag out..and a round chambered..Then fire that round, remove the mag and check before firing the next time, and repeat.. thanks for your help..Btw the bolt does only go in one way and the key to the wedge is in out position..I used the manual yesterday to check all the obvious points. I would like to remove all doubt that the rifle is READY..

[ttwn0324]

I'll put my two cents in here. I'll admit not an expert on these guns. I didn't have mine for very long before selling it. But, I know if you ride the charge handle closed it will not lock in. The charge handle is non reciprocating, it is only there to be used to unlock. And, as much leverage and force you need to use to unlock it, the same goes for locking it. You have to let it slam shut. The Semi-Auto HK's have the trip lever removed, so yes the hammer can fall when it's not in battery. The only thing that doesn't allow for a full out of battery firing is the way the the bolt carrier group is designed. The locking piece cannot move forward enough for proper fire pin protrusion with the rollers out of lock. With that said, that doesn't mean it can't or want fire in a case like yours, from the force of the hammer hitting it. This is why head space, firing pin protrusion and even primer sensitive are important. What is coming when not in full battery and might be technically the wrong term, is a hang fire. Where there is a shallow dent in the primer, it just didn't fire. Now, on to the way the cases looked. These have fluted chambers, so carbon on the base is normal. I can't so much more about them. But, obviously you seen something that wasn't normal about them. As for some of the causes the won't allow for full battery. Sticking rollers, Roller retaining plate or pin is damaged, Charge handle spring may not be seated correctly to allow it to fully seat, weak or damaged recoil spring. Those are some of the simpler things to look at. For problems with it firing out of lock, you need to inspect for wear or damage in the bolt group that is allowing enough fire pin protrusion to fire when out of lock. I just have to ask, what type of ammo were you firing?

[Old Guard]

Good morning,,I took it back out yesterday..Your details made me check the charging handle and assy..There was some cloth cleaning material in the tube for the bolt carrier..100% correct as to the position of the cocking handle, it must be locked, and does it when released..No letting the bolt close slowly..Anyway it seems the oil on the claw that holds the bolt back was not good enough.I put some lubripate on the claw..It was keeping the carrier from closing and locking the bolt..The wedge key can be put in only one way..The bolt must be locked in a clockwise direction. I started looking into the port to be sure it was locked before firing..It fired 10 times before, not locking.I pulled the charger half way back and released so i did not lose the shell..it fired 3 more times rapid fire, then i slowfired the rest..One mag fired due to neighbors in area.The Brass was coming out with the strip marks, and light carbon a usual.So alls well with that part.I was firing Maltese Nato Surplus, I have fired a bunch of it. Final note the charging handle and insert have zero gap.Anything in there could cause the bolt not to fully close off the barrel.The HK manual is for a G-3, it fails to mention any of these small details. Maybe these discussions will help anyone else whom shoots this type rifle..BTW, I bought brand new 1969 buttstock, forearm , and brand new mags fromSportsmans guide..this was great in that it had new recoil spring and buffer in the butt..They a beautiful green, but new.. Thanks Tim for allowing space for OTHER rifles..Later OG.

[TommyD11730]

Have you posted oven on the H & K forums?

http://www.hkpro.com/forum/hk-reference-library/78043-field-stripping-bolt-carrier-assembly-diagrams.html

[Old Guard]

Have you posted oven on the H & K forums?

http://www.hkpro.com/forum/hk-reference-library/78043-field-stripping-bolt-carrier-assembly-diagrams.html
Tommy thank you so much, now I can go back thru it again..I misplaced my password to Hk pro...So sure enough some gave me the exact diagram..I will try shooting it on Wednesday. OG