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ebutler462 · April 12, 2007, 08:28 PM

Found this on another forum. It is a Browning design pump.

There are some small points to be aware of with these older 520/620 designs. There is normal operation of the hook that interrupts the hammer engagement to the trigger, up until the bolt is closed and the action slide is fully forward and locks. That also frees the hook holding the hammer, just like on older Ithaca 37's, etc., but the hook CANNOT re-engage the hammer if you operate the slide release to check the chamber, for example.

If you do not then also pump the bolt sufficiently to the rear to re-actuate the hammer-cock part of the sequence, the hook is not engaged to prevent unintended hammer fall if you happen to pull the trigger.

If that happens when a shell is chambered, some wear on other parts may allow that shell to fire without the lock-up being fully engaged, with damage to the locking hole in the frame being a definite possibility. When the bolt slide (part just below the bolt body) is back a certain amount, it's rear edge now functions as a hammer block, so there will not be a strike against the tail of the firing pin if the trigger is pulled.

Try these tests with an empty gun to verify that yours operates in such a manner.

Pump the gun closed, operate the slide release, pump the bolt back enough to see the locking block start to drop down out of the square notch in the top of the frame, now pull the trigger. Click.

This cannot happen with the more modern designs of such new guns as the Winchester Model 12, Remington 870's, Mossberg 500's, and others, as long as the parts fit is still good.

These 520/620 style guns will be OK for use as long as the shooter recognizes the proper sequence of operations that will allow safe use, and you might consider having that gun properly disassembled and cleaned of the 50 year old varnish that used to be oil.

This info came from kirbythegunsmith.

April 12, 2007, 08:28 PM	#9
ebutler462 Senior Member Join Date: March 16, 2007 Location: NC Posts: 437	Found this on another forum. It is a Browning design pump. There are some small points to be aware of with these older 520/620 designs. There is normal operation of the hook that interrupts the hammer engagement to the trigger, up until the bolt is closed and the action slide is fully forward and locks. That also frees the hook holding the hammer, just like on older Ithaca 37's, etc., but the hook CANNOT re-engage the hammer if you operate the slide release to check the chamber, for example. If you do not then also pump the bolt sufficiently to the rear to re-actuate the hammer-cock part of the sequence, the hook is not engaged to prevent unintended hammer fall if you happen to pull the trigger. If that happens when a shell is chambered, some wear on other parts may allow that shell to fire without the lock-up being fully engaged, with damage to the locking hole in the frame being a definite possibility. When the bolt slide (part just below the bolt body) is back a certain amount, it's rear edge now functions as a hammer block, so there will not be a strike against the tail of the firing pin if the trigger is pulled. Try these tests with an empty gun to verify that yours operates in such a manner. Pump the gun closed, operate the slide release, pump the bolt back enough to see the locking block start to drop down out of the square notch in the top of the frame, now pull the trigger. Click. This cannot happen with the more modern designs of such new guns as the Winchester Model 12, Remington 870's, Mossberg 500's, and others, as long as the parts fit is still good. These 520/620 style guns will be OK for use as long as the shooter recognizes the proper sequence of operations that will allow safe use, and you might consider having that gun properly disassembled and cleaned of the 50 year old varnish that used to be oil. This info came from kirbythegunsmith.