sheared base screws

[Buck Fever]

I looked at that patent application and it is a scope rail locating tab on the recoil lug.

I can't really tell why they think it is better than the ARC version (which is mentioned in the patent) except the tab fits in a pocket that supports the rail in both directions instead of just the recoil direction.

Instead of spending $228, you could just buy a $35 Nucleus recoil lug and a $40 scope rail, notch/bed it and save $150.

 

[Unoboats]

Ya you need to or get it pinned. I epoxy every one I do, to remove you just have to heat it and the epoxy releases.

Use release agent as in bedding a rifle on the receiver and it will come off as needed, looks as though bedding the rail to level it out on receiver will help a lot as the receiver is not true most likely. Especially with light rifles and heavy recoil it will shear the rail mounting screws even when tightened down to specs.

 

[Ace Quackhunter]

While at the range yesterday I noticed my scope was loose. When I came home, I removed the scope and found both forward base screws broken off. I was able to remove them from the action, and replaced them with new ones. I torqued base screws to 20 in-lbs and put the scope back on. Back at the range today, after 15 shots, I noticed the scope base was loose again. Came home and found the 2nd from front screw sheared off and the other 3 all loose. Other than going up to #8-40, what else can I do? Also, what could be wrong that is causing this?

Christensen Arms Ridgeline
300 RUM w/ Area 419 Hellfire brake
Nightforce A295 rail
Nightforce 6-screw ultralight rings
Nightforce NX8 4-32x50View attachment 189069View attachment 189070

I had the same thing happen twice to the same rifle. I just went with bigger screws and it has never happened again.

 

[bigngreen]

Use release agent as in bedding a rifle on the receiver and it will come off as needed, looks as though bedding the rail to level it out on receiver will help a lot as the receiver is not true most likely. Especially with light rifles and heavy recoil it will shear the rail mounting screws even when tightened down to specs.

Using release agent defeats the ultimate purpose, I've literally done hundreds by cleaning both surfaces and epoxying the rail to the action, removal is zero issue.

 

[Unoboats]

The purpose is to give the rail and receiver a leveling platform to evenly mate the rail to the receiver, I've done hundreds of these as well and even in Kimbers with 300WM recoil and never a sheared screw. The epoxy takes out the uneveness in the rail and the receiver. But you are equally allowed your opinion. Just my 2 cents

 

[bigngreen]

I think some don't understand what the screws and bases are actually doing here, the screws are purely for clamping force, that have little ability to resist shearing if they are locating the mount. The fit between the mount and action is what should be taking the load because of the clamping force, you need to get the maximum surface contact between the mount and action then you screws have no horizontal load only the clamping they are made for.

 

[Unoboats]

I think some don't understand what the screws and bases are actually doing here, the screws are purely for clamping force, that have little ability to resist shearing if they are locating the mount. The fit between the mount and action is what should be taking the load because of the clamping force, you need to get the maximum surface contact between the mount and action then you screws have no horizontal load only the clamping they are made for.

agreed

 

[bigngreen]

The purpose is to give the rail and receiver a leveling platform to evenly mate the rail to the receiver, I've done hundreds of these as well and even in Kimbers with 300WM recoil and never a sheared screw. The epoxy takes out the uneveness in the rail and the receiver. But you are equally allowed your opinion. Just my 2 cents

I used to just bed the rail and have it release on the action till I started rebarreling rifles for a second and third time's and finding even pinned and bedded rails with slots pounded into the rails.

 

[Unoboats]

I used to just bed the rail and have it release on the action till I started rebarreling rifles for a second and third time's and finding even pinned rails with slots pounded into the rails.

Makes sense

 

[Buck Fever]

Do you mean the screw mounting holes are turning in to slots or something else?

 

[gator378]

Locktite does nothing for shearing screws only makes it a pain to remove screws.
I use the same epoxy I bed the rifle with, I bed both the action and rail at the same time.

Blue Loctite removable Red Loctite pretty permanent unless carefully heat. I am a big Fan of Loctite. good success rate

 

[new2mud]

I use Seekins rails since they incorporate a recoil lug. Takes the shear force away from the screws.

I had an issue with a heavy scope causing ever so slight movement under recoil and drove me mad thinking it was a load/barrel issue, but it was the scope rail. Lesson learned—I now only use a rail with integrated recoil lug.

 

[D-mon]

Regarding that extended recoil lug stoping the rail from moving, the old Remington Mohawk already had them last century! Nothing new here.
Regarding Kimber, their factory screws are 8-40 already so that is half the problem solved and can explain why they would not break.

 

[floyd kittrell]

We experienced this problem using a lead sled with no brake on 300 ultra mag .