Shotgun picatinny rail ?

[Gman]

I would like some advice about drilling/tapping a picatinny scope rail to an older Benelli M1 Super 90, Monte Feltro 20 gauge shotgun. This scattergun is a dedicated turkey/deer slug lead slinger with Williams Fire sights mounted on the ventilated rib. Problem #1 is my tired old eyes can't line up the iron sights no longer, so I want to mount a thin aluminum picatinny rail on top of the receiver with a pair of Ken Farrell 1" pic aluminum low rings holding a Nikon Monarch 1.5-4.5x 20mm scope. Problem #2 is that these older Benelli's aluminum receiver is very thin on top. I have read that it is too thin to drill/tap. There was a manufacturer of a Weaver style scope ring mount named Da Mar that had 6 mounting holes. (3 on each side) The holes were thru the mount on the radiused part (which wrapped around the top of the receiver) and were drilled/tapped in the receiver on 45 degree angles, thru the curved part of the receiver because it is thicker in aluminum at that point. Problem #3, Da Mar is no longer in business.

I really don't want to buy a newer 20 gauge shotgun which has the receiver drilled/tapped from the factory but I also don't want to ruin this older Benelli. This shotgun has never had one "failure to fire" other than the very light "youth" target loads and has harvested numerous bucks & gobblers. It only weighs 5 3/4 pounds with the 24" vent rib bbl and it is my favorite hunting scattergun.

Suggestions Please!

 

[Paul Hilgedick]

To start out I know very little about shotguns but thinking outside the box. Could the reciever br drilled and the base drilled and tapped then the screws inserted through the reciever into the base.

Just A Thought

Paul H

 

[Gman]

To start out I know very little about shotguns but thinking outside the box. Could the reciever br drilled and the base drilled and tapped then the screws inserted through the reciever into the base.

Just A Thought

Paul H

I don't believe that there would be enough clearance between the rearward moving action parts (inside of the receiver upon firing) and the screw heads.

 

[STS]

The receiver is not too thin to drill and tap. The tactical models come drilled and tapped from Benelli. I have done two of them, and if I remember correctly, the receiver is .150 thick. I made a base and mounted a Leupold Delta Point Pro on both. It's aluminum and should be threaded accordingly.

 

[Gman]

The receiver is not too thin to drill and tap. The tactical models come drilled and tapped from Benelli. I have done two of them, and if I remember correctly, the receiver is .150 thick. I made a base and mounted a Leupold Delta Point Pro on both. It's aluminum and should be threaded accordingly.

Thanks, I'll have my smith look at it.

 

[Walt Krafft]

I have a Winchester M12 that I wanted to mount a red dot on, but didnt want to drill and tap it. I used JB Weld to mount a piece of rail. It has survived several thousand rounds now. Many of them buck or slug loads. Try it, if it falls off, then explore drilling and tapping.

 

[Gman]

The receiver is not too thin to drill and tap. The tactical models come drilled and tapped from Benelli. I have done two of them, and if I remember correctly, the receiver is .150 thick. I made a base and mounted a Leupold Delta Point Pro on both. It's aluminum and should be threaded accordingly.

I pulled out the action bolt and took some thickness measurements of the receiver. I measured .075" in the top center at the front, in the channel/groove. You are correct, it is much thicker at the rear of the receiver vs the front. I believe that I will order a picatinny rail blank from EGW and ask my smith if he wants the job. I will get him to mill the bottom of the rail blank to the width of the channel groove that is in the top of my receiver for the lowest mount possible. Then he can drill/tap the 4 holes in the thicker rear of the action.

Thanks Again!!!

 

[STS]

I pulled out the action bolt and took some thickness measurements of the receiver. I measured .075" in the top center at the front, in the channel/groove. You are correct, it is much thicker at the rear of the receiver vs the front. I believe that I will order a picatinny rail blank from EGW and ask my smith if he wants the job. I will get him to mill the bottom of the rail blank to the width of the channel groove that is in the top of my receiver for the lowest mount possible. Then he can drill/tap the 4 holes in the thicker rear of the action.

Thanks Again!!!

Exactly!! If you will relieve the sides of the rail so that it sets in the channel, the base will not deface the receiver finish, and it will also be a more solid attachment. The screws will be on the centerline and result in a metal to metal connection as opposed to trying to clamp over a 'bridge.' I would encourage you to consult your gunsmith regarding the screw size and pitch for the job. Your run of the mill 6-48 sight screw, would be a poor choice in an application of significant recoil from a shotgun, and in an aluminum receiver.

 

[Gman]

Exactly!! If you will relieve the sides of the rail so that it sets in the channel, the base will not deface the receiver finish, and it will also be a more solid attachment. The screws will be on the centerline and result in a metal to metal connection as opposed to trying to clamp over a 'bridge.' I would encourage you to consult your gunsmith regarding the screw size and pitch for the job. Your run of the mill 6-48 sight screw, would be a poor choice in an application of significant recoil from a shotgun, and in an aluminum receiver.

What screw size/thread do you recommend?

 

[STS]

I would ask your gunsmiths opinion of an 8-40. I used something similar to that.

 

[DRK]

What screw size/thread do you recommend?

I just did two Benellis for Pic bases. Used 8-40s on both, bases came from EGW. Worked perfectly.

 

[akajun]

So I use a Williams red dot with their corresponding base.on my two turkey guns
A rem 11-87 I had to drill and tap and a benelli sbe2 which was tapped from the factory

The Remington reciever is pretty thin over the barrel but I could still get 3 threads in it with a 6-48 screw.
Also the benelli even from the factory is pretty thin but again, 3 threads with a 6-48
I’d go with 6-48 for more thread engagement rather than a stronger screw with a 8-40
The threads will be your weak point

 

[STS]

The weak point in this application isn't the screw threads. It's the threads in the aluminum receiver. The very reason not to use a 48 tpi screw. Three threads of a 48 pitch screw is .060 long. The Benelli receiver is approximately .150 thick if I remember correctly. It would be foolish not to use the entire .150.