Information in the pictures and typed here in the write-up is generally the same. I just wanted it typed out so everything is searchable.

If you would like to see this information presented in a video demonstration with live-fire examples, please use the link at the end of the write-up.

Pic 1:

Title slide with DIY adapters/spacers installed. Keep reading for tube specs.



Pic 2:

Prior to 2016, Mossberg 590 & 590A1 shotguns with an 18.5” barrel had a 5 round solid magazine tube. These guns were “6-shot” capable with a 5+1 capacity (5 rounds in the magazine tube. 1 in the chamber).



Pic 3:

In 2016, Mossberg introduced “7-shot” capable 590 and 590A1 shotguns. These guns still had the 5 round solid magazine tube but now came with a +1 magazine tube extension.

These guns are identical to the pre-2016 guns. Only difference is a mag extension vs cap. Guns came from factory in this configuration.



Pic 4 & 5:

Mossberg 835 shotguns used the same 5-round solid magazine tube that is found on the 590 and 5901 at this time.

Since they used the same magazine tube, the location of the barrel forend lug on the 835, 590, and 590A1 is located in the same place on all these barrels.

So, unless special circumstances apply, Mossberg 835 barrels will fit on these 590 and 590A1 shotguns perfectly.



Pic 6 & 7:

Around 2018, Mossberg “evolves” the 18.5" 590 and 590A1 to have a solid, one piece, 6-round magazine tube. This retains the 6+1 capacity without the need for an extension. This evolution moves the barrel forend lug forward almost two inches meaning that 835 barrels, and older 590 and 590A1 barrels will no longer properly fit on these guns.



Pic 8:

835 barrels, as well as older 590, 590A1 barrels will fit on this new 6-round magazine tube if the gap between the forend lug and the magazine tube cap is filled. That gap can be filled with a 1" diameter steel or aluminum pipe cut to 1-13/16" which is 1.812 inches or 46mm. 1" black iron or galvanized steel pipe can be found at most hardware stores. 1" schedule 40 Aluminum pipe can be found at most metal supply shops or online. 



Pic 9 & 10:

590 and 590A1 shotguns with a barrel length of 20” are “9-shot” capable with an 8+1 capacity. They have a solid, 8-round magazine tube. The barrel forend lugs from an 835 to this variant of a 590 & 590A1 are much farther apart leaving about a 5-inch gap between the barrel forend lug and the magazine tube cap.



Pic 11:

835 barrels will fit on this 8-round magazine tube if the gap between the forend lug and the magazine tube cap is filled. That gap can be filled with a 1" diameter steel or aluminum pipe cut to 5-3/8" which is 5.375 inches or 136.5mm.

1" black iron or galvanized steel pipe can be found at most hardware stores. 1" schedule 40 Aluminum pipe can be found at most metal supply shops or online. 



Pic 12:

Many types of 1" diameter pipe cut to the right length will fill the needed gap. From PVC, to steels, to aluminum.

I don’t recommend PVC. It lacks durability with recoil and degrades under a hot barrel.

Steel is readily available, but can be heavy when using the longer pieces. Aluminum is the best overall option with a great strength to weight ratio.



Pic 13:

Most, if not all Mossberg 835s are chambered for, and designed to use up to 3.5” shells, meaning that it can properly cycle and safely shoot 3.5”, 3” and 2.75” shells.

590 and 590A1s are chambered for, and designed to use up to 3” shells meaning that it can properly cycle and safely shoot 3” and 2.75” shells.

When you put an 835 barrel that is chambered for up to 3.5” shells on a 590/590A1 receiver that was designed to accommodate up to only 3” shells, it will not cycle 3.5” shells properly.

There is a Failure to Feed 99.99% of the time. If the 3.5” shell is forced into the chamber and fired, there is a Failure to Eject 100% of the time.



Pic 14 & 15:

Factory & aftermarket magazine tube caps and extensions have ridges on them that interact with the detent in the barrel forend lug. This keeps your cap/extension from walking loose which keeps your barrel securely attached and in the correct position.

Smooth spacers/adapters don’t interact with the ridges or detents so it doesn’t prevent your cap/extension from walking loose. This may be remedied with lock washers, thread locker, tape, routine tightening etc.

My development on this project stopped here because machining these spacers with ridges stopped being worth my time, energy, and money. Maybe someone else will bring one to market someday, but for now, I’m ok with using a simple 1" steel or aluminum pipe to put any Mossberg 835 barrel on virtually all Mossberg 590 and 59A1s. 



Pic 16:

The Mossberg user manual says, “835® Models are designed for factory loaded 12 gauge 2-3/4”, 3”, and 3-1/2”shotshells. Do not fire slugs of any type (single projectile ammunition) through the overbored 835® Accu-Mag™ barrel. This barrel is designed to shoot lead or steel pellet shot loads only. Use only 835® barrels designated specifically for slug shooting.”



Pic 17:

If you would like to see all of this information presented in a video demonstration with live-fire examples, here is the link to that video:

[https://youtu.be/lxFybdC7Ygs?si=kobOpVHeTOzHXYVZ](https://youtu.be/lxFybdC7Ygs?si=kobOpVHeTOzHXYVZ)

Thanks!

835 to 590 & 590A1 Barrel Interchange Guide.