Opinions on light load cycling problems?

[Jogar80]

A couple months ago i took my 7 yr old boy out dove hunting and a friend’s son let him shoot his 28ga semi auto. My boy loved it so I went out and bought him an SA-20 thinking the 20 gauge would serve him better in the long run. AFTER the purchase I realized that Mossberg says the gun should cycle 7/8 oz loads and up, but I was hoping it would cycle 3/4 oz loads for less recoil. I bought some Fiocci Trainers which are 3/4 oz @ 1075 fps and fully expected a whole lot of nothing but, to my surprise, they cycled just fine and my boy was very happy. I was giving it a cleaning this week when I noticed the barrel was not fully seated the whole time we were using it. This was due to the forend stock not being fully seated against the receiver. Once I seated the stock, the barrel dropped down another good 1/4”. Went out to try it again and now it won’t cycle the Trainers anymore. Bolt blows back just enough for the brass on the shell to show and stops there.

Why would fully seating the barrel cause the shells not to cycle? Could the cause be something else? I know that cycling a load like those Trainer rounds is probably a lot to ask of a 20ga semi auto but I really want this thing to work the way my boy liked it. Any ideas, suggestions, opinions? I’m all ears

 

[Jmm14534]

Maybe the brass is expanding and causing just enough pressure on the bore to make extraction difficult. A couple of things. Make sure the bore is scrubbed clean of any lub or fouling. Try and break it in with some heavy loads to loosen things up. Fire 2 or 3 boxes at least. After the break in completely disassemble and clean again.

 

[Jogar80]

I have fired several hundred rounds of heavy loads. Taken apart and cleaned. Still won’t cycle the light Trainer rounds. It’s just weird that i unscrew the cap by 3-4 turns and unseat the barrel by 1/8 inch and the trainer rounds work wonderfully. Is there any danger in running it like this? I’m considering making like a 1/8” thick washer to go between the barrel and receiver

 

[Jogar80]

3/32” unseated is what it takes to make it cycle

 

[Jmm14534]

I think the “unscrewing” helps lessen the return spring tension and is not a result of the barrel being out of battery.

If you want to try and clip a couple of turns off the return spring that may do it. Start small, one turn at a time until you get it dialed in for the light loads. Call Mossberg to get a new spare one for when you’re son graduates to a full load.