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Discussion Starter #1
I have owned an "IB" date code HK 91 since the early 80's. Along the way I ended up with a complete spare bolt carrier w/ bolt-head. I think I may have swapped the bolt-heads out at one point many years ago. I am trying to figure out which of these two IB dated bolt heads are the original bolt head for my HK91, and what the other markings mean ("DL", "J", "N" and "C").

Also does each new bolt-head contain rollers that are head spaced to the rifle, or are the HK91/G3 new bolt-heads interchangeable between rifles? Could any of these markings mean that the bolt-head was rebuilt and has different rollers to accommodate for locking shoulder wear?

 

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Any time your change anything in the roll lock triangle, you need to check the bolt gap to make sure. The triangle includes the locking piece, bolt head and the rifle (i.e. trunnion / barrel), which the rollers are between these three items (some debate on the bolt head but best to check when changed ;-). The roller size is the first pass adjustment tool for bolt gap, followed by the remainder of the locking piece / bolt gap and then the trunnion / barrel.

Thus the sort answer is try the other bolt head and check bolt gap.
 

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The bolt, carrier, & locking piece from the original gun will have the last 3 digits of the gun's serial marked on them. The photo's you took don't show the part of the bolt that show the ser#. Usually, the numbers are marked on the bottom. Bolts usually came from HK with standard size rollers [8.0] as the factory installed the barrel & trunnion assembly correctly, so oversize rollers were not needed for new factory guns.
 

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The bolt, carrier, & locking piece from the original gun will have the last 3 digits of the gun's serial marked on them. The photo's you took don't show the part of the bolt that show the ser#. Usually, the numbers are marked on the bottom. Bolts usually came from HK with standard size rollers [8.0] as the factory installed the barrel & trunnion assembly correctly, so oversize rollers were not needed for new factory guns.
I have never seen that on a civilian hk rifles.... Youll see that on some military g3's, not on 91's.
 

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Discussion Starter #5
The bolt, carrier, & locking piece from the original gun will have the last 3 digits of the gun's serial marked on them. The photo's you took don't show the part of the bolt that show the ser#. Usually, the numbers are marked on the bottom. Bolts usually came from HK with standard size rollers [8.0] as the factory installed the barrel & trunnion assembly correctly, so oversize rollers were not needed for new factory guns.
The civilian models HK91, HK93, HK94 do not have serialized parts. Only the receiver has a serial number on these models.
 

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Discussion Starter #6
Any time your change anything in the roll lock triangle, you need to check the bolt gap to make sure. The triangle includes the locking piece, bolt head and the rifle (i.e. trunnion / barrel), which the rollers are between these three items (some debate on the bolt head but best to check when changed ;-). The roller size is the first pass adjustment tool for bolt gap, followed by the remainder of the locking piece / bolt gap and then the trunnion / barrel.

Thus the sort answer is try the other bolt head and check bolt gap.
I just checked my bolt-head gap for both bolt carrier assemblies. One complete assembly has a .011 and the other complete assembly has a .009 gap. If I swap locking pieces the gap measurement swaps between assemblies (gap follows locking piece). I find this strange because this gun only has fired about 2000 rounds since new. Oh well.

So I need to order new rollers for both bolt-heads. Given these measurements, which number rollers should I order? Do I need any other replacement parts to do the roller job other than the rollers?
 

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+2 rollers and a brand new HK locking piece from RTG parts, will put you where you need to be bro.Those are some nice looking HEADS,civillian or not;they are german as can be. LOL
 
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