Symptoms of Short Stroking?

[Deanimator]

Can anybody help me out with symptoms of short stroking in a semi-auto shotgun.

I've owned numerous semi-auto handguns and rifles, but never a semi-auto shotgun.

The gun's a brand new gas operated SDS AR T-02.

The first time I shot it (with full power buckshot loads of various types) I would generally get a stoppage on the second to last or last round.

When this happens, the shell stop seems to be disabled, allowing a round to exit the magazine tube, tying up the gun by lying on top of the shell lifter.

Playing around with snap caps, I noticed a similar behavior unless the bolt handle was FORCEFULLY pulled to the rear.

I'm thinking that it's possible that the gun is sometimes short stroking, preventing the action from fully cycling. As I said, the gun is new and that model has a reputation for requiring break-in. I've added a +2 magazine tube extension, the spring for which seems excessively long/powerful. While cleaning and lubing the gun, I reinstalled the OEM spring, which seems to work much better in combination with the extension.

As I've said, I'm new to semi-auto shotguns, having only POSSIBLY shot one once before.

Any advice would be appreciated.

 

[PapaG]

Take the extension and strong spring off, put it back to original and shoot a hundred break in rounds.

 

[Deanimator]

Take the extension and strong spring off, put it back to original and shoot a hundred break in rounds.

Thanks. It just so happens I bought 100 rounds of Estate 00 buck a couple of weeks ago. I won't be able to shoot again until Sunday, after work.

 

[bersaguy]

I've always been told premature ejection is the symptom of short stroking your shotgun...

Ok, sorry, had to.... But yes, as @PapaG says, take the extension off for now and run some rounds through it. If you can run a 100 or so rounds without any major malfunctions, try putting the extension back on, load the tube with your snap caps and let it sit for a few says with the mag tube spring fully compressed, then see how she runs

 

[Deanimator]

I've always been told premature ejection is the symptom of short stroking your shotgun...

Ok, sorry, had to.... But yes, as @PapaG says, take the extension off for now and run some rounds through it. If you can run a 100 or so rounds without any major malfunctions, try putting the extension back on, load the tube with your snap caps and let it sit for a few says with the mag tube spring fully compressed, then see how she runs

Unless something comes up, I'll be taking it to the range Sunday after work.

I've got the OEM magazine cap and spring installed. The first five snap caps I ran through it fed and ejected properly, then things went downhill. I don't know if my arm was getting tired, or what.

That bolt release is INCREDIBLY stiff. I took to hitting with a plastic hammer. I also lubed it generously to the extent that I could without stripping the gun. I can't help but conclude that the feeding issues and the difficulty with the bolt release are somehow related. We'll see how much 50-100 rounds of 00 affect the break-in.

 

[Deanimator]

Twenty five rounds each of 0 and 00 buck through the gun today (with the OEM spring and cap) without a single misfeed. I lubed it like an M60, but I don't know that that made a difference. I had to keep some blue shop towels on hand to wipe the Clenzoil off while shooting it.

Will try it with the OEM spring and the extension next Sunday.

Correction: Have to work Sunday. Range is closed on Monday, so will have to test with the extension on Tuesday.

 

[Deanimator]

Got the dovetail to Picatinny rail today. It's WAY more solid and stable than the one that came on the gun.