H&R M48 Topper Pop open problem

[Sneaky]

I have an old 1948 H&R Topper 12 gauge that was given to me by my grandfather. It shoots and everything seems to operates fine and locks up tight, But when i shoot it, the breech pops open and if you get pelted in the forehead with an empty case.... ( dont ask me how i know this) anyway is this a common issue with these? Is there an easy fix for this like a spring or something thats worn out?
Any advice or suggestions would be appreciated.

Thanks in advance

[G-Man WC]

Pop opens are caused by inadequate lock up, you can check the latch engagement?
Here you go bro.

-g

http://www.angelfire.com/ma/ZERMEL/gapfp.html

http://www.go2gbo.com/forums/hr-centerfire-rifles/barrel-fitting-for-the-novice/msg504758/#msg504758