old single 12 unlocks after every shot

Riven

Riven

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I just refinished an old single shot i got at the gun show. Took it out for the first time to day & after every shot the barrel was opened 1/8" or more.
Lock up is solid & tight so i dont know the reason for it to be doing this other than my thumb possibly riding the lock lever during recoil.

Any other suggestions to what it could be?
 
You wold think you would be able to make it pop free if it was worn or a weak spring but you cant discound 12ga recoil i guess.
I have it on it every way i can think to the poit of hurting my hand and it wont budge.
 
The only sure way is with a chamber guage Brownells has them.

https://www.brownells.com/gunsmith-...ber-gauges/shotgun-chamber-gauge-prod593.aspx

But that's only half the issue. The forcing cones on old shotguns were very short as they were using cellulose wads to get a better gas seal, modern forcing cones are longer for use with plastic wads. During the twenties and earlier a common size shell was 2 9/16 inch if you old shotgun is this size a 2 3/4 inch shell might fit as the actual size is 2 1/2 inch the extra 1/4 inch is for the expansion of the case. Firing a 2 3/4 shell in one of these guns would force against the shorter forcing cones and cause higher pressures potentialy being dangerous and also causing wear and damage to the hinge assembly, also causing very loose actions and a increase in recoil.
 
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Make sure the area where it engages is clean and dry. You don't want any lube or oil of any kind on the latching area so that it locks up nice and tight.
 
Maybe not wall hanger material yet. A gunsmith can ream out the chamber and forcing cones to fit modern 2 3/4 inch shell. But the cost of this fix is probably over half of what the shotgun is worth.
 
WobblyHead said:
Ok fist thing do not use modern 2 3/4 shot shells you gun may be pre SAAMI and may not have a 2 3/4 inch chamber which could be causing your problem and be potentially dangerous. So first off I would find out when it was made and what shells are safe to fire in it.
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Riverside Arms Company is a trade name used by the J. Stevens Arms and Tool Company on various types of firearms. So, the gun is basically a Stevens and it may be much later manufactured than 1913. The patent was from 1913 and that is stamped on the barrel and not the year of manufacture.

Also, I doubt that excessive pressure causes the gun to open. There are videos showing some guys firing a taped .50 BMG in an old 12 ga. single shot (looks like a Cooey or Stevens) and that thing didn't even budge.

An easy/inexpensive way to figure out if the gun doesn't open with 2 1/2" shells is to shoot one. What I've done before is using a 2 3/4" shell, cut the crimp/top off and fill with wax on top so the pellets don't fall out. Now you have a 2 1/2" shell because 2 3/4" is measured on a fired shell with open crimp and not on an unfired shell.

Now, if your gun opens up you know it's not from using 2 3/4 shells.

RR
 
So i had the chaber checked. It is 2.75 chamber and the forcing cone recut to a modern taper.
Now to take her out for a test fire and see if she needs new springs as well.
 
I've run into this a few times.
Use a candle, or smoke lamp, to check the contact between the locking block and the engagement on the barrel. If it's not a good fit, the 'flip-up' will stress it and cam the block back enough to open the action.
My 2 cents.
 
Riven said:
I just refinished an old single shot i got at the gun show. Took it out for the first time to day & after every shot the barrel was opened 1/8" or more.
Lock up is solid & tight so i dont know the reason for it to be doing this other than my thumb possibly riding the lock lever during recoil.

Any other suggestions to what it could be?
Click to expand...

First time I took my Cooey 84 out it did the same thing till I made a conscious effort to keep my thumb away from the locking lever, it wasn’t happening as much with target loads but slugs and old CIL 3” mag shells it was happening more. Definitely was me riding the lever and heavy recoiling loads didn’t help the matter, repositioning my thumb solved the issue. The gun locks up tight and is in good condition, I chalk it up to using pump guns more than anything. Same can be said for the forend on a pump gun with a stout load if you don’t have forwarded pressure on the forend, it always opens the action under recoil.
 
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