Mossberg 151 breech plug spring -- what does it do?

[mcaswell]

I recently inherited some rifles, a Mossberg 151M among them. It has an issue with double (and sometimes triple) shots. I'm fairly sure I solved that problem by cleaning the firing pin.

Upon taking it apart, however, I discovered it's missing the breech plug spring. I'm trying to track down the part, but I'm curious -- does the spring actually do anything? Either my dad or grandfather must've reassembled the gun without that part at some point, so I'm not sure it's essential.

The part in question is this one: https://cfnparts.com/Mossberg Model 151M(b) & 151M-B Rimfire Rifle Parts-297?product_id=9262

 

[gunrunner100]

As far as I can recall, it's designed to prevent the breech plug from rotating and coming out of the receiver. There are striations on the plug that coincide with a raised area on the spring, an audible "click" can be heard when rotating the cap into the receiver. Not a critical part if you're aware to watch for the plug backing out.

 

[mcaswell]

As far as I can recall, it's designed to prevent the breech plug from rotating and coming out of the receiver. There are striations on the plug that coincide with a raised area on the spring, an audible "click" can be heard when rotating the cap into the receiver. Not a critical part if you're aware to watch for the plug backing out.

Thank you very much, that makes perfect sense now that I look at the plug. The spring is nearly impossible to find, so I'll have to live without it for now.