Guys,
My dad went on a recent waterfowl hunt trip with his Steven's 311 he has had since new. He was shooting two and three quarter inch heavy steel waterfowl loads and it seemed to him his top lever was possibly coming open. since they do not have an under lug and just a wedge type top lever is this possible? He was wondering if it was being done subconsciously because he trap shoots so maybe he was doing it with his thumb and not realizing it. He's just use the gun for upland hunting until now that's a nice tight gun so just getting your guys thoughts if it's the loads that could be doing this? And I guess he should be laying off of the those from now on. Now you will get something better suited for the loads he's using

Thank you I appreciate it

As said, the locking mechanism on the Stevens is a simple hook on the top lever that engages the top rib extension



You did not mention the age of the gun, but the top lever spring could be getting tired.
More likely, yes, "he should be laying off of those loads", in a gun with barrels that were not designed for steel.

He shouldn’t be using heavy steel loads in a gun not designed for it. A double gun coming open when firing is due to the angle of the locking engagements being too severe, and not being “locking tapers”. If angles are too severe the mechanical forces applied to the locking engagement upon firing will overcome the angle and mainspring. A weak mainspring could also be a part of the issue, although in my opinion stiffening the mainspring is a bandaid. Consequently of angles aren’t enough you have nothing/little accounting for wear.

I think it was no less than W.W. Greener who wrote that the upward force of a shotgun was so gentle he could hold one with no lock at all together with his index finger. I expect Gunmaker is correct that the problem is wear on the locking engagement...Geo

Should be simple matter to remove the toplever and take a look.

It's probably from the 70s and it's probably hasn't been shot much at all over the years that's why I say it's in pretty good shape and tight he just started using these loads in it this last time other than that it's just had regular field loads. Maybe some shur shots #5's for grouse that's probably the biggest.that's why it surprised me with little wear I just imagine it's too heavy of a load for the gun do you guys think it did any permanent damage?

If it is self opening now with the heavy loads I think it is most likely permanently damaged and needs fixing. Try regular shells in it and see...Geo

There are a couple of Yt videos showing doubles in slow motion during firing. There is obvious movement in the top lever in one case, a Citori, and in the hammers of a muzzle loader in another. The Citori top lever can be seen oscillating during recoil, and that oscillation most likely is due to more than just worn locking botl angles. I will post links when I find them.


Apparently inertia forces play a role in the movement of bits during recoil, both in the rearward phase as well as in the braking phase when the gun stops on the shooter's shoulder.

First; it would seem to be that as the gun recoils upward there could be a tendency of the barrels to want to tip open due to their inertia. Different makers compensated for this by various means.

I seem to recall reading at some point in the past that when applying pressure to tapered engaging points that friction will keep them from moving up to about 7°. Beyond that 7°, one is counting on the spring pressure to keep the bolt in place. I do not know what angle Stevens cuts their bolt to, but Lefever states in their catalogs after they went to this type of bolt it is cut on a 15° angle. I have never had one of mine show any tendency to open.

I've seen numerous Browning O/Us that open themselves after the first shot. Not Superposeds, but later guns without any abuse or neglect. Must be something about the design.

SRH

The late Mike McIntosh in one of his books on doubles mentioned this problem with a few early production NID guns- something about the radius of the top bolt where it cams into the top rib extension, if memory serves.

25 years ago maybe, I owned and shot a 12 Super Fox HE-- no problem with 2&3/4" Federal Premium loads, but when I went to the same loads in 3"-- the top lever would move out of battery when the gun was fired-- Go figure.. RWTF

Stan,
Superposed will do the exact same thing if the locking bolt and top lever spring are worn or broken. The cool thing is....anyone, and I mean anyone can put in a new spring or locking bolt very easily. The Citori & it’s clones are a lot of new shotgunners first “fancy” gun....most of them care for them cosmetically...But mechanically abuse them. Slamming them shut, not cleaning them properly, etc. most will continue to shoot the gun even though they suspect something is not right too.
The height of the Superposed & Citori receiver is most definitely crucial to the design.