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Discussion Starter · #1 · (Edited)
Figured I would share this information with the board as it might help someone out. I posted some of this info earlier, but have finally fixed the rifle and wanted to share my experiences.

I have an IB date coded HK-91. Picked it up used several years ago and never had a problem with it. Then early last year, it started *really* recoiling heavy during a long shooting session. Figured it was a buffer problem as I had installed a heavy buffer a few months prior.

I replaced the buffer, but to no avail. The recoil was still fierce. I then read about bolt gaps on 91s that should be within .1 - .5 mm, others saying .3-.5 mm. Not sure which is correct. Anyway, I purchased a gauge and mine measured out to below .1 mm. Can't remember the exact reading, but there wasn't much space left. No problem - just replace the rollers with +2 and we'll be good to go - NOT. Apparently, the person who originally owned my rifle actually shot it quite a bit. When I put the +2 rollers in there, it measured out to the same gap. Yikes. Time for +4 rollers. That fixed the gap to .279, but I wasn't satisfied leaving +4 rollers in there. Luckily no dimples had formed on the back of my receiver from firing with the smallish bolt gap. Getting a sore shoulder and cheek will make one refrain from shooting a rifle too much.

In the meantime, I had measured the gap on my Vector rifles, each with no more than a few thousand rounds through them, and here's what I found:

V93 - .331 mm
V53 SBR - .406 mm
V51 SBR - .381 mm

It seemed that .3 - .4 mm was the sweet spot as far as bolt gaps go, and not only was I not in that spot with my real baby, but it appeared to be one worn beyotch. Not good.

While I knew trunnions can wear, they sure are hard. I wondered what would happen to the bolt gap if I purchased a brand-new-in-the-bag locking piece and bolt head from reputable sources. I located a new locking piece from Robert with RTG Parts and a new bolt head from Adam with HKParts.net. The results were interesting and ultimately very satisfying.

Again, with the original LP and bolt head along with +4 rollers, the gap was measured at .279 mm.

I changed out the LP only, and the gap increased to .305 mm. That's a step in the right direction I thought.

I then replaced the bolt head as well, remembering that this came with 0 rollers. The gap shrunk back, but only to .279 mm again!

I then put in some +2 rollers along with the new bolt head and new locking piece, and I arrived at the magic # - .381 mm. Jeff was again happy.

I have yet to shoot it, but I plan on running quite a few rounds down range and then re-testing the bolt gap to ensure it remains in the .3 - .4 mm sweet spot. While I'm sure my trunnion is worn somewhat (along with my barrel, though it still looks real good), these new pieces have given my baby a new lease on life.

Questions/comments are welcome.

Regards,
Jeff
 
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Any idea what the gap should be on a 93? I dont think the rifle was shot very much at all, but I woul like to check. I have not been able to find this if online yet, so I just joined this forum.

Thanks, Andrew
 

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Until recently, it never occured to me that changing the bolt head could affect gap. but it most certainly can. The forward edge where the rollers go in and out can wear down.


Thanks for an excellent post!
 

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Jeff,
Thanks for the insight. What tool are you measuring the gap with?
 

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was it hard to open the action before?
 

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ALSO NOTE:
if installing +2 rollers dont get it back in ball park also install a new LOCKING PIECE
then try the +2 rollers..bet ya get a better gap..
ya might have to go with standard rollers..

the min gap = .005" in OR .127MM thats a point in front guys
(time to fix and fast) keep it above.008" = .203mm

the max gap =.020"in OR .508mm
most run best in the .012" = 305mm
to .018" = .457mm

it's easy to get it there


Duke
 

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Discussion Starter · #10 · (Edited)
I was using a standard feeler gauge I purchased at Sears Hardware. Nice thing is, each "finger" of the gauge shows both the english and metric measurement.

Action was the same to open as before. I only noticed the issue when my right cheek became sore as hell from some really nasty recoil upon shooting it. As I said before, I guessed at first (wrongly, as it turned out) that the buffer was bad. Never thought of the bolt gap until a lightbulb went off in my head, then the process started....

BTW, I had a chance (finally) to put around 200 rounds through it. After taking it apart and cleaning it, the gap hadn't changed, and I was happy....

HTH,
Jeff
 

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Until recently, it never occured to me that changing the bolt head could affect gap. but it most certainly can. The forward edge where the rollers go in and out can wear down.


Thanks for an excellent post!
Yep, same here. Once you are aware of it, you look at the roller locked drawings and wonder how you didn't realize that from the beginning.
 

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Thanks Jeff. Will head over to Sears and buy a better set. The set I have now is the cheap-o.
CS
 
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I am unfammiliar wiht the companys that sell the replacement bolt,rollers, ect.

Does anybody have the websites?

Thanks in advance!
 

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RTG have funking looking + size rollers (cups at ea end)
adam webber also have real Hk made rollers that look like the ones that come out of Hk's
(just so ya know)
 
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I used a feeler gauge and could fit the .005 into the gap with no issue. I could feel the .006 had a little resistence. So the gap is .005?

He told me that he hadn't fired it much...

Thanks for the help!
 

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The feeler gage that has some drag is the one that gives the actual reading
 
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