Rust in the barrel - what now?

Good evening Folks, I have to repeat this question.

We are at the coast for a few days and my edc pistol has light rust in the barrel.

How do I proceed, and what general maintenance plan does one follow?

Get a brush and gun oil and scrub it clean.
Patch until clean, then push very lightly oiled patch through and leave it.

To add to the above, I would wipe the pistol with a lightly oiled cloth on all metal surfaces with ballistol. Wipe off excess with cloth.

Light rust shouldn't make much difference and the pistol should still be safe to fire. Heavy rust that reduces bore diameter is dangerous; this is the same as a bore obstruction. Once the rust have been removed, you should be good to go.

Once you remove the rust you will be left with pitting. Heavier the rust the deeper the pitting. Light to moderate pitting will increase pressure and velocity slightly because the bore is rougher, but should still be safe to fire. Deep pitting decrease the pressure due to the bore getting bigger. I think it should be safe enough to fire. Your friendly gunsmith should be your guide in that case.

There are plenty of well-abused examples out there that still shoot without exploding. Failures are usually due to mechanical parts.

Use a phosphor-bronze brush with a thin oil of your choice. Paraffin, WD40, Q20, diesel and/or Ballistol all work. Use copious quantities. Brush until the rust is gone. Do not reverse brush direction inside the barrel. Patch until barrel is dry inside. Then patch with a slightly oiled patch with gun-oil of your preference. I prefer Ballistol.

Good evening Folks, I have to repeat this question.

We are at the coast for a few days and my edc pistol has light rust in the barrel.

How do I proceed, and what general maintenance plan does one follow?

Out of curiosity, what brand and model is your pistol ?

Hopefully you manage to get it sorted, all the best.

Good evening Folks, I have to repeat this question.

We are at the coast for a few days and my edc pistol has light rust in the barrel.

How do I proceed, and what general maintenance plan does one follow?

Out of curiosity, what brand and model is your pistol ?

Hopefully you manage to get it sorted, all the best.

S&W MP9, I have had similar experiences with most of my firearms.

I sweat what seems to be concentrated acid. Have found that Herschells wax spray is a superpower for non-stainless guns. Local product and i can highly recommend it. A very light application left to dry protects my beat up and finish compromised primary carry pistol worn inside the waistband for 30+km of walk up shooting in the freestate over a long weekend. For the barrel I lightly spray a patch and pull it through once. Hasn't failed me yet and chrony testing says it doesn't make a measurable difference to velocity.