r/canadaguns • u/BenisBickler • 26d ago
Fix my gun Bolt Group Issue
Found a piece of my SBI LPC bolt carrier, about as big as a finger nail clipping, in my trigger group while cleaning it after a range day.
Picture is of the BCG damaged.
Is it still safe to fire or is the BCG compromised?
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u/Q-Ball7 In the end, it's taxes all the way down 26d ago edited 26d ago
Fine, with an asterisk.
Firing pin protrusion is mediated by the bolt length, so you shouldn't be ending up with pierced primers.
The real question is why it broke. My money's on SBI cheaping out on this part- that part of the part should not be rough, and it suggests to me that part was machined from a casting (and the part you saw was some surface defect that chipped off somehow). Not that it being a casting or of milder steel is bad, because the carrier bears no pressure, but for a thousand dollars in 2019?
Why does the section underneath the part that broke off appear to be black? I'd expect that to be metal-colored (this gun isn't especially dirty), but if it's black itself, maybe it was always cracked and the surface treatment got in there? What does the underside of the broken piece look like? Is it black too?
I don't believe that the firing pin should ever be hitting that part. Install the BCG (without the firing pin) into the upper, lock the gun fully into battery, and observe that the bolt's tail is slightly proud of the hole.
If it's recessed, you have a different problem, and you'll want to check the relevant bolt dimension, and rule out the firing pin dimensions being wrong (even though the overall length is correct the other sections of it may not be).