What can cause this problem?

[Dark&Good]

My semi-auto shotgun worked perfectly through the first 200 rounds of Brenneke Black Magic 3" slugs (the only ammo I used so far). But yesterday, it would either not cycle at all, or just open up the action half way. I had to pull it back, shake out the empty hull (wasn't stuck at all), and let it slide forward. About 50% of the times, I had to push it forward to chamber the next round.
I thought that the newer barrel (chamber) is causing this, so I went back to the range today with the older barrel, that always worked perfectly - same problem.
Do you have any ideas what's causing this? Or how can I find out?

[Blue]

Have you cleaned and lubed it?

[tlillard23]

Are you using the same ammo?

Did you happen to oil it up prior to use, and maybe wipe it down after the last trip?

Did you put a pistol grip on it? the PG absorbs some of the recoil and does not allow some semi's to cycle reliably

[Dark&Good]

I cleaned and lubed it, yes... just like before.
Same ammo, yes.
No pistol grip, it's the same setup that worked so well...

[Fjold]

It would help to know what make and model shotgun you have.

Did you take it apart when you cleaned it?

Did you check that all the O rings/buffers, etc are all installed in the correct positions?

[richnstef]

i almost guarranty its a remington 11-87 and its the o-ring blown out.change the o-ring and it will be perfectly fine im almost 100% positive. i had one that did the same thing. buy a few o rings and always keep them with the gun just in case good luck

[Dark&Good]

Yes, I take it apart when I clean it (how else could I clean it?)
It's a H&R Excell Auto 5 (model SA1128).
I have cleaned it about 10-12 times so far, I am very careful of putting everything in the right place.

[Dark&Good]

The O-ring doesn't show any difference, either... and the piston is in the "magnum" mode, too.

[Dark&Good]

Can you think of ways, how to find the source of this problem?

[MAX100]

Put the piston on the standard load end and make sure gas ports on the barrel are clean.


GC

[Dark&Good]

Ok.

[Dark&Good]

To sum it up for anybody who encounters the same problem, under very similar circumstances, the possible causes can be:
1. propellant, plastic and lead residue (especially in the gas ports)
2. ammo with less propellant
3. insufficient lubrication
4. lessened recoil because of special grips and/or stocks
5. incorrectly installed parts
6. damaged O-rings or other parts

Handling consists of checking above 1, 3, 5 and 6, and correcting accordingly.
If the problem persists (or no issues were found with 1, 3, 5 and 6), using a more sensitive piston setting ("standard" instead of "magnum") should solve the problem, since that handles above 2 and 4, too.

Well, I turned the piston around to "standard", I'll let you all know about the results, after my next range trip (in a day or two).

THANK YOU, guys.

[Dark&Good]

I couldn't go as planned, but I'm going at 11 am.
I'll post the results when I get back home.

[Dark&Good]

Off to Chabot

[Dark&Good]

Sooo... it works perfectly.
I didn't have a single hiccup; 40 shots of Brenneke Black Magic 3"s fired. I just turned around the piston.
Accuracy was amazing, too. Thank you for the help.