A buddy of mine has a Mossberg that has been in the closet for the last 5-6 months. he pulled it out for a good cleaning and couldnt get the choke tube out. He finally started getting it and it got really hard...so hard in fact, that he had to get a pipe wrench to finally get it out. The threads were perfect both on the choke tube and the gun. The next tube went in super easy. He put the bad tube up to the barrel and it was a bigger diameter than the barrel.

So what caused this? He has never shot steel shot through the gun, not even once.

there's lots of questions needing to be answered and i for one would love to see some pics. but let me just say this, if he is sure that was a original factory choke and it has bulged then chances are any other choke he screws into that same barrel has the potential to not engage enough thread to keep it there when he fires it. i would advise your friend to have the gun checked out by a smith or contact mossberg to have it sent in for evaluation before someone gets hurt.

Good point. He did say when I asked that it seemed a little loose.

just toss the bad choke into file 13 and replace it

I think he threw it away. I told him to dig it out if he had to dumpster dive but I am not sure if he did. I will ask. The barrel shows no obvious sign of bulging.

I was just curious to see if anyone had any ideas on what may have caused this.

sounds like a screwed up or damaged thread on the choke

If it was inside the barrel before, then that statement can't be true

I see this happen all the time...

What happens is that grit and debris from powder, primers and plastic wads gets forced into the threads over time. Add a little oxidation, and the tubes can get welded in there pretty tight under pressure.

To remove them safely, the ends of the barrels may need to soak in Kroil for a week to avoid damage...a pipe wrench is not the best tool for the job here.

My solution is that choke tube threads need to be lubed with anti-seize. Oil or grease doesn't work. They're often not lubed as they come from the factory, and the factory may even be inclined to screw them on too tight.

It's also a good idea to unscrew the tube and re-apply the anti-seize as part of the normal cleaning process to make sure they stay loose.

Yep. A schmear of Anti-Seize on the threads is never a bad idea.

For anyone that may experience resistance like this in the filter, a week long soak in Kroil will work it's way in there and make it a bit easier to remove. Btdt on a buddies choke.

I use Birchwood Casey choke thread lube on all my screw in chokes

https://www.birchwoodcasey.com/Cleaning-and-Maintenance/Choke-Tube-Lube-Grease.aspx

He stated that when he held it up, it was visibly bigger than the hole it was supposed to go in. In other words, it expanded when it was removed. The threads were not full of gunk, he screwed the next one in very easy....in fact, he wondered if it was too easy. The guy is a pretty knowledgeable guy, I wouldnt doubt anything he said. Crazy, I know. That is why I posted this conundrum here!

Obviously it's one of those 21st-century choke tubes made out of miracle polymer instead of steel. They never vibrate loose, and the constriction automatically adjusts to the range of the shot!

You answered your own question.

Don't forget they never dirty with plastic, or powder residue.

Ha! yeah, it being a Mossberg is about 99.9% of the problem!

He is as baffled as I over this. It just doesnt make sense. He was really confused when no way would it go back in its hole, but the full choke went in easily.