Bittereinder
CGN Regular
- Location
- Ontario (GTA)
I recently tried something that seems to work well and thought it might be useful for others. Or maybe others have tried something similar and there's something bad about this that I'm not aware of or haven't seen.
The punchline so you don't have to scroll. I did this.
Background to bypass the "why don't you just..." questions
I've found that I just can't get a very good sight picture with the iron sights on a Mossberg rifled barrel for slugs (on a 930 or 500). But I don't like the idea of putting a rail on and off when I switch between the slug barrel and the regular smooth bore. This is to avoid eventually damaging the receiver if I keep doing it, plus it's annoying to do that annually and re-zero. I want an optic dedicated to the slug barrel and leave it on. I guess a lot of you just have a dedicated slug gun and that's probably the best way to go, but I only have so much space and budget.
And the cantilever barrels are hard to come by. Probably I should have just bought multi-barrel kit, but I ended up with two JM Pro 930s (one for myself and one for a son) and I really like the ergonomics on those. I'm still looking for a cantilever rail rifled barrel for my other 930 (I have a WTB posted).
The solution
So, the problem is, how can I mound a red dot on a non-cantilever rifled barrel? I considered trying to fit an EGW red dot mount to the dovetail, but I probably would've had to file the dovetail on one of those to make it fit, and they're not cheap.
It turns out that parts from the rear sight of a Mossberg rifled barrel can be used to mount a short rail.
Here is what the Mossberg dovetail mount looks like, with the rear sight base off to the side sitting on the barrel. The screw pins the sight base to the barrel. (This is from a Mossberg 500 barrel that I also have; I didn't think of taking pictures of this stage when I was doing the work on my 930 barrel.)
Note the circular opening at the bottom of the sight base. More on this below.
After initially trying a shorter rail, I ended up using one of these. Basically, I needed a section of Weaver or Picatinny rail with a curved base that would fit nicely on the barrel. This one, #403, is meant for a Remington bolt action, I think, where presumably the receiver has a rounded top similar to this rifled shotgun barrel. What I needed was a short rail with a slot and a screw hole close to the centre. With the factory sight base in hand, I just looked through the Weaver section in a few stores until I found one that looked right.
Note that the little dovetail plate sticks above the rounded barrel top, and because this Weaver rail doesn't have the large circular hole in the bottom like the Mossberg sight base does, I had to file the edges of the little dovetail plate that slips into the barrel. This allows the rounded contour of the Weaver base to fit snug against the barrel. Sorry, I forgot to take a picture of the small dovetail plate after it was filed but it's pretty straightforward.
It turned out that one of the screws that came with the rail was the same size (#8 I think) and close to the right length. The screw with the Mossberg base was a bit short for this Weaver rail, but one of screws that came with the rail was the perfect length after filing a bit off the end of that screw.
The finished product
Here's what my Venom red dot looks like mounted on the barrel. I used red loctite on the screw because I figure this is pretty harsh recoil for one small screw. I mounted through the centre hole of the rail. I decided to plug the other hole with JB Weld so that crap won't accumulate in there. Maybe a better solution is to have a gunsmith drill and a tap the barrel for that second hole, but I want to see if this will work without making any permanent modification to the barrel.
(same picture as above)
Using this setup, I was able to get roughly 1" groups at 50 yards. I put 10 slugs through this so far and the base hasn't loosened. I wouldn't trust the strength of this to a remote hunting trip, but for southern Ontario farmland I think it'll be ok.
An alternative I rejected
I first tried this using one of these #76 Weaver rails.
Here it is on my other 930. This also could do about 1" at 50 yards, but I found there was a bit of play in the mount. The red dot could very slightly rock forward and backwards and I didn't like that. Didn't seem to affect accuracy, but I wanted a perfect fit so I went with the longer rail shown above.
The punchline so you don't have to scroll. I did this.
Background to bypass the "why don't you just..." questions
I've found that I just can't get a very good sight picture with the iron sights on a Mossberg rifled barrel for slugs (on a 930 or 500). But I don't like the idea of putting a rail on and off when I switch between the slug barrel and the regular smooth bore. This is to avoid eventually damaging the receiver if I keep doing it, plus it's annoying to do that annually and re-zero. I want an optic dedicated to the slug barrel and leave it on. I guess a lot of you just have a dedicated slug gun and that's probably the best way to go, but I only have so much space and budget.
And the cantilever barrels are hard to come by. Probably I should have just bought multi-barrel kit, but I ended up with two JM Pro 930s (one for myself and one for a son) and I really like the ergonomics on those. I'm still looking for a cantilever rail rifled barrel for my other 930 (I have a WTB posted).
The solution
So, the problem is, how can I mound a red dot on a non-cantilever rifled barrel? I considered trying to fit an EGW red dot mount to the dovetail, but I probably would've had to file the dovetail on one of those to make it fit, and they're not cheap.
It turns out that parts from the rear sight of a Mossberg rifled barrel can be used to mount a short rail.
Here is what the Mossberg dovetail mount looks like, with the rear sight base off to the side sitting on the barrel. The screw pins the sight base to the barrel. (This is from a Mossberg 500 barrel that I also have; I didn't think of taking pictures of this stage when I was doing the work on my 930 barrel.)
Note the circular opening at the bottom of the sight base. More on this below.
After initially trying a shorter rail, I ended up using one of these. Basically, I needed a section of Weaver or Picatinny rail with a curved base that would fit nicely on the barrel. This one, #403, is meant for a Remington bolt action, I think, where presumably the receiver has a rounded top similar to this rifled shotgun barrel. What I needed was a short rail with a slot and a screw hole close to the centre. With the factory sight base in hand, I just looked through the Weaver section in a few stores until I found one that looked right.
Note that the little dovetail plate sticks above the rounded barrel top, and because this Weaver rail doesn't have the large circular hole in the bottom like the Mossberg sight base does, I had to file the edges of the little dovetail plate that slips into the barrel. This allows the rounded contour of the Weaver base to fit snug against the barrel. Sorry, I forgot to take a picture of the small dovetail plate after it was filed but it's pretty straightforward.
It turned out that one of the screws that came with the rail was the same size (#8 I think) and close to the right length. The screw with the Mossberg base was a bit short for this Weaver rail, but one of screws that came with the rail was the perfect length after filing a bit off the end of that screw.
The finished product
Here's what my Venom red dot looks like mounted on the barrel. I used red loctite on the screw because I figure this is pretty harsh recoil for one small screw. I mounted through the centre hole of the rail. I decided to plug the other hole with JB Weld so that crap won't accumulate in there. Maybe a better solution is to have a gunsmith drill and a tap the barrel for that second hole, but I want to see if this will work without making any permanent modification to the barrel.
(same picture as above)
Using this setup, I was able to get roughly 1" groups at 50 yards. I put 10 slugs through this so far and the base hasn't loosened. I wouldn't trust the strength of this to a remote hunting trip, but for southern Ontario farmland I think it'll be ok.
An alternative I rejected
I first tried this using one of these #76 Weaver rails.
Here it is on my other 930. This also could do about 1" at 50 yards, but I found there was a bit of play in the mount. The red dot could very slightly rock forward and backwards and I didn't like that. Didn't seem to affect accuracy, but I wanted a perfect fit so I went with the longer rail shown above.
Last edited:
