I'm 3rd owner of a Sav12 6mm br that I bought on this site. It's been a good one but the pin sticks out from bolt face by more than .052 & BR4's pierce once in awhile with rather mild loads (450's don't). Of the many rifles that I've owned over the last many years, this is only the second that's done this, turned the pin down .006 on the AR that was punching primers too hard and it's been good for 1500 rounds. My question is the. 052 out of spec? Should I disassemble the bolt & shorten the pin & profile it back to what looks like the factory radius? Seems that I read something here that indicated firing pin travel can effect accuracy. Got an open mind on this & would appreciate any information or comments. Thanks Jim
excessive firing pin protrusion
- Thread starter jimsr
- Start date
Although you may know already, the protrusion is adjustable. Set it to .035" or as close as the lock washer will allow. Remember, regardless what the bench setup is the primer anvil stops the firing pin forward movement at about .018"-.020". You could set the protrusion to .100"and all it would do is shorten the pin fall about .080"!
Which brings up the issue or cratering and blanking. If you look close at the factory pin tip profile you'll see its ground on a taper from the shank out. Since the primer stops the pin forward travel the taper allows a gap between the pin hole and pin.
On the left is a factory pin and on the right one re-ground to a radius from the tip to the shank. Hopefully you can see on the factory profile how far the taper extends back into the pin shank compared to the one on the right I reshaped.
The same pins in the same bolt head set for to .018" protrusion, about the same amount the pin indents a primer.
The factory profile on the left, the reshaped pin on the right. Notice the gap left between the pin and pin hole on the left.
Now, the next question, what radius? I haven't a clue. It was trial and error until I got it right then made a gauge to match. I grind them to match the gauge then set to protrusion.
Bill
Which brings up the issue or cratering and blanking. If you look close at the factory pin tip profile you'll see its ground on a taper from the shank out. Since the primer stops the pin forward travel the taper allows a gap between the pin hole and pin.
On the left is a factory pin and on the right one re-ground to a radius from the tip to the shank. Hopefully you can see on the factory profile how far the taper extends back into the pin shank compared to the one on the right I reshaped.
The same pins in the same bolt head set for to .018" protrusion, about the same amount the pin indents a primer.
The factory profile on the left, the reshaped pin on the right. Notice the gap left between the pin and pin hole on the left.
Now, the next question, what radius? I haven't a clue. It was trial and error until I got it right then made a gauge to match. I grind them to match the gauge then set to protrusion.
Bill
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