• 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.

Ulti-Mag Miss-Fire


Copper BB
Good morning. I'm new to the thread in search of help. I have a Ulti-mag that is somewhere around 15 years old. It's seen a LOT of use. Last year I started having problems with the occasional misfire where the pin would strike the primer but the shell didn't fire. I tried new shells, different brands, same result. The problem has progressed to the point that it will rarely fire a shell at all. I saw an old post by darcerly0810 on April 12, 2012 on the exact same problem I'm having but I did not see any post on resolution to his problem. The following is what I've done so far:

1) Complete disassembly of the gun including the bolt, clean, reassemble, same problem.
2) I Had the gun and trigger assembly ultrasonically cleaned, same problem.
3) Replaced the firing pin and firing pin spring, same problem.

If I jam the forearm forward to put a new shell in as hard as you possible can, it seems to fire every time. But, when I cycle through under normal, reasonable pressure, it will not fire.

Any thoughts? Is replacing the entire trigger assembly next?




I'm Your Huckleberry
Staff member
Global Moderator
Have you inspected.the barrel? Is there a buildup that is preventing the rounds from chambering completely without excess pressure?

I would also check where the bolt and barrel look up to make sure there is not excessive wear or buildup in that area.

Another thing I might check is the hammer spring.


Copper BB
Yes, that is what led me to having it ultrasonically cleaned as I wanted to make sure there wasn't build up I wasn't getting. The gun is VERY clean at this point! I did look to see that the chamber was fouled but didn't see anything and it seemed that if the shell wasn't fully seating in, it would actually be closer to the pin and not further. Is there any way that your aware of to measure the clearance between the bolt and barrel to make sure it is far enough forward into the chamber area?
I contact Mossberg a couple of times. The rep yesterday said they would not sell me a hammer spring, that I would need to go through a gunsmith? If it seemed reasonable that it could be the issue, I see that I can buy an entire assembly at Brownells.

Thanks for the response.

Also, I did notice that one of my extractors was really worn but I didn't think that would play into this problem. Do you? In my research I saw a post on that issue by mikerowbury and mine look just like his did in his post.


I'm Your Huckleberry
Staff member
Global Moderator
Do you have a friend with Mossberg or access to another barrel? Even mossberg 500/535/590 barrel would work as longg as you can swap the magazine tube as well. Curious as to whether changing barrels makes a difference.

For that matter you could also swap trigger groups as well.

If you have access to another 835 try swapping the bolt out. (Separately from the barrel.)

My gut is telling me that either the barrel is not seated fully into the receiver, the rounds are not chamering fully or the locking lug is worn/blocked and is not seating fully.

With the slide forward how much play do you have? Do you see the bolt moving or is the play only in the slide?

I would try swapping parts try and narrow it down before I bought a new trigger group.


Hi TXTurkey. Welcome to the Mossberg Owner forum from E TN.

First, I am not an armorer or gunsmith, so if anybody disagrees with me they are probably right. And I don't know the 835 specifically as to its design, but I'd suggest you take a good look at the locking mechanism as MikeD suggested.

As a general caution, I suggest you do get advice from someone with training in shotgun actions. I caution against willy-nilly bolt swaps until you are advised that is safe. As a Garand shooter I take this advice:


This especially applies to the M1's bolt and the military did not allow bolt swaps except thru their armorers.


.270 WIN
First question on misfires....how are the primer strikes? Normal or light? Normal strike and no boom means ammo. If the primer is hit normally and shows a good dent, the gun did its job, the ammo didn't. Doesn't matter what brands you tried....if you tried fifteen diff brands and got good hits on all of them and all misfired, then you have fifteen bad boxes of shells. The second path of the Y is a light strike. If you load and shoot the gun normally and get a light strike, start at the front of the firing sequence and work your way back. Pin, pin channel, pin spring, trigger group, hammer, main spring.

A well used gun developing probs, you're looking at either grit/burrs/dirt or weakened springs. Main spring is the first thing I'd suspect. Switching out the trigger group would be my first trial fix.

Switching out the bolt is perfectly safe. And a 500A bolt can be used to check it if you need to.


.50 BMG
Shotgun shells headspace on the rim.

If the rim of the shell is not locking up tight between the chamber & the bolt, the shell will move towards the muzzle when the firing pin hits the shell.

Maybe the strike looks pretty good. but it just didn't hit the Anvil in the primer hard enough.

From what I understand, most misfire is not related to the ammo but are caused by too much headspace or a poorly seated primer. Instead of striking off, either the primer or the entire shell moves forward when you fire.

I have experienced this with my own hand loads.