Issue with cycling a stevens model 520

I shoot Trap with my 520, but only Singles.

Every time I shoot doubles, part #53 (see here: http://www.gunpartscorp.com/Manufact...348.htm?page=5 ) disconnects from the block, so the foregrip just slides back and forth! This ONLY happens when I have one in the barrel, and one in the magazine. I shoot the one in the barrel, and then PUMP, and thats when it disconnects!

I have never had this issue with just singles. I normally insert the shell right into the barrel, and then close the breech. Also can also load it from the bottom, or from the magazine tube... but only with ONE shell. If I SHOOT, then cycle ANOTHER shell, the handle disconnects. It seems the gun knows when there is 2!

I have checked and rechecked for worn parts, but nothing looks particularly worn down. Also everything is nice and tight including the front of the magazine tube that if twisted lets you take the gun apart. I have tried to recreate the issue with snap caps with no avail.

Anyone run into this issue?
https://scontent.cdninstagram.com/hp...23995997_n.jpg
https://scontent.cdninstagram.com/hp...41365359_n.jpg

Howdy,
First let me say that is one pretty pre-1915 Stevens 520, if I had to guess I'd say 1909-1913, and it's great to have folks out there hunting and busting clays with these wonderful old guns. Did you do the refinish?

Your problem is interesting. At first I would say that either the slide bar or the carriage was worn, causing them to slip apart under the force of chambering a round. I'm assuming from what you've said about everything being tight that the barrel is fully seated in the receiver and the locking lugs are not protruding down. It looks from the picture that everything is flush but if not that could cause a slight misalignment that could affect already worn parts.

http://www.shotgunworld.com/bbs/cpg1...6/IMG_1925.JPG
http://www.shotgunworld.com/bbs/cpg1...6/IMG_1926.JPG

But you say that it only happens when you have a second round in the magazine. Could it possibly be that you use more force when loading the second round from the magazine as opposed to hand loading the first round (ie maybe you're pulling worn parts apart)? If that isn't the case then you've got to look at how the lifter, cartridge stop, and the cartridge affect the carriage during the loading process.

The carriage, In the first pic above, sits in a machined groove in the left side of the receiver. The breech block rides on top of it. The left side of the carriage, second pic above, has very little up/down movement but on these early guns there can be some flex on the right side. Stevens corrected this in a later design by adding a lip to the bottom right side of the breech block that rides in a machined groove in the right side of the receiver. Unlike on your gun this anchors both sides of the assembly to the receiver.

http://www.shotgunworld.com/bbs/cpg1...6/IMG_1930.JPG
The lifter has a spring loaded arm on back that is activated by the movement of the carriage. If this is stuck for some reason the lifter arm may be putting more pressure on the carriage as it cycles. Once again causing the carriage to lift up on the right side and affect the connection w/ the slide bar.

http://www.shotgunworld.com/bbs/cpg1...6/IMG_1915.JPG

The cartridge stop is a rocker design (see above), the screw directly under the middle of the ejection port is the pivot screw and the one in front of it is a set screw that makes the front end of the stop push away from the receiver and block cartridges from leaving the magazine tube. The carriage hits the ends of the cartridge stop on its way forward and back causing it to change positions. If it is sticky, you may try backing off that forward set screw (front edge right side of receiver) to reduce the force required by the carriage to operate the stop. It may be putting pressure on the carriage causing it to move just enough to loose the grip on the slide bar.

Also look to see if there is any way that the cartridge is putting pressure on the slide bar and somehow forcing it loose as it is moved into the chamber.

Anyway I hope this helps. I have developed an identification guide for Stevens 520 shotguns, if you're a Stevens nut you may find it interesting.
http://www.shotgunworld.com/bbs/view...p?f=5&t=430907

James

Hi, My first post when I was researching the same problem. I tested my 520 after I cleaned it up and found it worked fine loading one shell at a time then I tried 2 and the slide bar disconnected when cycling after the first shot which locked-up my bolt to the rear. I took it apart later and inspected the parts but could not see anything wrong. When I run live or dummy shells with a full magazine it cycles great but I only seem to have problems when I fire the live rounds.
I will try your advice and see what happens.