Hi, Seamus! 'Got your excellent pamphlet about two and a half years ago. Totally outstanding execution in all aspects. I especially appreciate the ring binding and the plastic covers for protection.

These days, I just take off the foreend nut and spray the interior with AeroKroil (world's best anti-locking/anti-freezing oil) and let it sit a half hour or so while I'm cleaning the rest of the shotgun (Beretta AL391 Technys Gold). After that I do the press down to compress the spring (four or five times), lay in on some newspaper to drain off any crud and then wipe it off well and re-installl it on the Beretta. The nut stays clean. On the very first cleaning of the nut, I soak it with Kroil in a small glass canning jar overnight. This totally removes all the cruddy gunk. I do all subsequent cleaning (every five or six boxes or so of shells) as described at the beginning of my comments above. Since I've been doing that, I haven't worried about that forend nut again in the last couple of years or so. Works for me! Again, kudos for a totally outstanding job on the booklet.
Regards,
JohnA

Do you know if I can order a new one of those Red bushing things for the fore-end cap. I kinda tossed it.

Brownells has it http://www.brownells.com/.aspx/pid=2918 ... ED-PLASTIC

Regarding the red cap, you might try this. My used 391 did not have the red cap so I found that a hose nozzle washer fits on perfectly and prevents the cap from bottoming on the springloaded pin. See if it works for you!

I was doing the compression thing every time I cleaned the gun, every couple hundred rounds, and applying a couple drops of oil, yet it froze up solid on me during a round of skeet. Soaked it for a week in Liquid Wrench. Applied heat. Could NOT get it apart.
Then I really got dumb and ordered another one from Brownell's. YIKES! Shoulda bought the Briley. A much better design. Why Beretta uses that internal snap ring arrangement, I do not know. So much better to let the plunger bottom on a lip in the aft half of the nut and retain the spring with forward half of the nut screwing on. I went through two pairs of snap-ring pliers trying to deal with that rascal.
Other than that, Mrs. Lincoln,it's a great gun.

Maybe an old question covered elsewhere, but here goes..

I have acquired a 391 recently, the nose cap looked relatively clean but was jammed up solid, the plunger wouldn't move at all.. I've bought a new cap and the gun is usable, but I just don't want to let that frozen cap win. I've had it soaking in WD40 for about 3 weeks.. no change. I've tapped the plunger repeatedly with a hammer to try and break the seal - nil effect. I've tried squeezing the cap in a vice, to force the plunger further into the cap, nil effect.

Two courses of action remain.

Heat the plunger with a propane torch, to see if the seal breaks as it cools.. could also try a rapid cooling by dousing it with water. Would heating cause the spring to lose its temper?

Cut a couple of slots in the rim of the plunger, and see if I can break the seal with a rotary motion applied by a screwdriver.

Any other ideas?

Like I say, I don't want to lose this battle, with a mere piece of metal, if I can avoid it.

Would you be able to get the snap ring off it as it is? I don't know if it could have been assembled incorrectly, but just hard to believe with a vise it can be moved. Maybe it is frozen all the way collapsed instead and will no longer expand? Seems to be the snap ring would be the secret to making progress. I would choose a different solvent or penetrating oil. I would put it in a small container of Kroil for a few days. Later blow it out with an air hose. If you add heat do it gently and don't over do it. If it is locked up as you say then a couple of new parts including a spring would not be unexpected. Let us know how this turns out

Thanks Mm, the snap ring came out OK, so I think I will try an alternative solvent, and then maybe heat as a last resort. As you suspected the plunger looks to be at max depression, so the vice achieved nothing. I will let you know if there is any progress.

All the best.

I never understood why Beretta continued with such a complex gas compensating system when it is obvious from many other successful designs that it is not necessary. It was also not used in their 303 models and the like. Maybe Rube Goldberg got hired on as a design engineer for Beretta! LOL

I've admitted defeat, the cap has gone in the bin.

More soaking in penetrant liquids did nothing. Today I heated in with a gas torch, and then quenched in oil, that had no effect. Tried more hammering and squeezing in the vice, but the plunger must be recessed to its maximum.

Thanks all for the input though, much valued.