• Mossberg Owners is in the process of upgrading the software. Please bear with us while we transition to the new look and new upgraded software.

Who Has Done the Vang Porting/Backboring on a Mariner?

OK, I'm intrigued by this process, but I'm not seeing much posted here by people who have actually spent the long green to have it done and used it a lot.

Is it "worth it"? Subjectively or objectively, how much did it tighten groups or reduce recoil? How much does the porting lessen velocity? Does it make 590 barrels any harder to clean or oil?

In my case, I picked a Mariner decades ago because I needed a good finish for saltwater environments. It's held up great. Now I'm looking at paying someone a lot of money to drill a bunch of tiny holes through that finish? What does Vang do to protect the bare steel this drilling and the backboring exposes? Does Mossberg approve or disapprove of the Vang processes?

Not trying to be snarky, just want honest user reports.

I can't help you with your porting question BUT maybe you can help me with a Mariner question. Only IF I had a shiny Mariner, I would probably not want to drill holes in the barrel. ;)

Speaking of which, I'm picking up a 1990 vintage 590 20" with the "shiny" finish. Are these parts actually stainless vs "marinecote"? Info is very limited on them... :(
I don't know about the porting,but I found this old post from 2019

I found this, part of an old post,,,,,
Havlin replied:
590 marine cote made since 1988.
First finishes were high polished and looked like stainless. By 1992, they had dulled it down to a satin finish, still silver, and today the finish is almost a dull matte gray - the users didn't want the glare off the high polish finish so Mossberg adjusted.
None made with stainless, but that first finish looks that way and confuses many

What is your serial number?
I can't give you any advice reagrding damage to the the finish but can certainly talk about porting both a rifle and a shotgun.

There are both plusses and minuses when porting a barrel. Becasue you are expelling the gas earlier than normal you will see a small reduction in felt recoil especially with low brass shells. Typically you can expect 10-15% reduction in felt recoil. Maybe a little less with 3 inch magmum shells. Also associated with this porting your muzzle rise will be reduced slightly thus allowing you to get back on target quicker. The extent of the barrel porting impacts this rise.

Now for the minus part. The noise level felt by the shooter will be increased and anyone standing next to you, say at a firing range, out hunting or inside a building, will have a significant increase in noise. And, significant is the word! This, for most folks is the biggest drawback and a non starter for those who have been around ported barrels before.

The other minus is an increased signature from the unburned powder residue. With normal non ported barrels the flash follows the projectile out the end of the barrel and while visible has minimum impact on the shooter. However, in a ported barrel, especially a shotgun, you will see some of the the flash directed upward through the ports. Depending on barrel length this can be significant and especially at night the shooter tends to have decreased night vision and decreased ability to get back on target. This flash can impact reaction time.

Hope this short overview helps. There are a lot of factors that one should consider before porting a barrel IMO. I'd recommend you find a friend who has a ported barrel or rent a gun with a ported barrel to see for yourself if porting is something you want to do. Many 45-70, 444 or 450 guide guns have ported barrels if you know someone who has one.

Last edited:
My Mossy Onyx Reserve O/U has ported barrels right from the factory. It’s my primary sporting clays blaster. Recoil is light and getting on target after the first shot is fast. I know my shooting buddies have learned to be directly behind the me rather to the right of left due to the gassing. The porting does not hurt in any way a probably adds a little advantage in my opinion. Cleaning is a bit of a pain. When I do a thorough cleaning I have a method for cleaning each individual hole.

I don’t think the video has dropped yet but InRange TV is doing a “Vang” porting job on. Maverick 88. Keep your eye out for the video for at least one data point.

Last edited:
I also have a Mariner and I would like to have this done to it but I would be worried about the holes corroding so they would need to have the same coating put into them so I'll just pass on it. But that's just me ‍♂️. Besides I would have to clear it with the wife cause that's her secondary HD weapon after her Walther .40. And after 31yrs of marriage I've learned to just leave some things alone
I observed the Federal FlightControl performance went DOWN with the Vang Comp. Am I seeing things correctly?
Yes I thought the same thing but the Federal is still pretty impressive. The barrel porting is more for barrel rise and reducing recoil IMHO.
I observed the Federal FlightControl performance went DOWN with the Vang Comp. Am I seeing things correctly?
Pattern definitely seemed to spread a little more on the Federal after porting. Still pretty impressive though.
The whole package, Backbore, Forcing Cone, and Ports, come to $300!

That's a little pricey to me for what benefits it gives...

Opinions vary, I guess!