Winchester Model 50 12 GA jams on third round

[4v50 Gary]

Apparently the carrier lock swings out and prevents the third round from exiting the magazine. Any thoughts as to why?

Found a manual for the similar Model 59 (aluminium receiver and not steel like the 50).

 

[4v50 Gary]

Carrier stop screw is missing. That could be it.

 

[Urban_Redneck]

It may also be a weak magazine spring.

 

[Zeke/PA]

Could just need a good and thorough cleaning!

 

[4v50 Gary]

Thanks guys. I ordered the part from Jack First. It's not that I couldn't make it (and Brownell's Encylcopedia does have the dimensions), but presently I've no access to a working lathe