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Indeed ! Bolt Gap is very important and should be checked regularly. It's not some internet commando made up shit. If you're going to own these types of firearms I suggest you educate yourself about them thoroughly so you don't sound like an ignoramus saying bolt gap doesn't mean anything.
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Bolt gap is an indication of roller and trunnion geometry. Too small of a gap means the rollers are too far into the trunnion recesses. As a result the action unlocks easily/early and sends the bolt/carrier rearward at a higher velocity. In extreme cases, when the carrier hits the buffer the bolt will hammer back against the locking piece, pushing the rollers outward.
This will put dimples in the reciever channels and risks cracking parts you don't want cracks in.
It seems the guys at HK are a little smarter about this issue than at least one Arfcommer, just maybe.
Indeed ! Bolt Gap is very important and should be checked regularly. It's not some internet commando made up shit. If you're going to own these types of firearms I suggest you educate yourself about them thoroughly so you don't sound like an ignoramus saying bolt gap doesn't mean anything.
Granted it's been a few years, but this was a topic in the HK MP5 armorer's course I took with none other than Bob Schultz back in 2007. "Bolt Gap" is a checkup/maintenance thing, just like replacing gas rings or extractors on an AR. It's not hard to check on, you just need some feeler gauges and some knowledge on the roller sizes and their effect on the gap. The platform is pretty much the same across the board for the roller locked rifles, obviously there are changes in the dimensions and needed specs but the relationships are the same.
Put simply, if you measure the gap and the dimension is at/smaller than the minimum, you would install a + sized set of rollers. I don't remember what the size differences were or how much it affected the gap by memory, but it was straightforward. If the gap is too big, install a smaller roller.
You can look at HK Parts, if you ever wondered why there were different sized rollers and why people would even buy them, there you go. Better yet, snag a G3 Armorer's manual, they're straightforward and worth it.
http://www.hkparts.net/shop/pc/HK-91-HK-G3-Bolt-Group-c113.htm?pageStyle=h&ProdSort=19&page=2&idCategory=113