At what point would a pinned scope rail be a good idea, or addition to, over just 8-40 screws?
Pinned scope rails
- Thread starter SpencerC87
- Start date
Yes, several manufacturers make something similar, but my Borden BRM doesn't have pins and can't take a rem 700 rail with said lug.
DaveTooley
Gold $$ Contributor
Are you jumping out of aircraft? 6-48's worked for what a 100 years, 8-40's are a big step up.
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I put a 3/16" pin between the 2 rear screws on Remington and Savage actions after opening the screws to 8-40. They're heavily braked magnum ELR rifles with 2-3 pound scopes. Without the pin, four 8-40 screws on those rifles will work loose after several hundred rounds. Bedding the rail slows it down. Pinning shuts it down. I think the R700 is the worst offender here with the differing front and rear base elevations. Dimensional changes during polishing compound the problem. I also have a 300WM 5R R700 with an aggressive brake and 24 oz? tactical scope. It's on a bedded Seekins base that has an integral lugs The (4) 6-48 screws haven't come loose on that after a few hundred rounds. Any integral lugged base will need to be bedded.
My Magnum RPRs use (6) 8-40 screws to retain the rails. Same cartridges, same brakes, same scopes. I intend to pin them but haven't got around to it because it hasn't been an issue. Some of them are on their 3rd barrel.
I think that Borden action uses (6) 8-40 screws. For any cartridge and application it was intended for, with a sub 2 pound scope and no brake, my experience suggests you can just call it good. If it really bothered me, I'd turn the screw in the middle of the rear bridge into a pin.
My Magnum RPRs use (6) 8-40 screws to retain the rails. Same cartridges, same brakes, same scopes. I intend to pin them but haven't got around to it because it hasn't been an issue. Some of them are on their 3rd barrel.
I think that Borden action uses (6) 8-40 screws. For any cartridge and application it was intended for, with a sub 2 pound scope and no brake, my experience suggests you can just call it good. If it really bothered me, I'd turn the screw in the middle of the rear bridge into a pin.
So that's the line then, jumping out of aircraft? Dowels are never needed on any competition rifle? I ask because many custom action manufacturers are offering it, or even an integral rail. Borden has seemingly switched to adding dowels, or at the very least offer it and they are selling their new scope rails with dowel holes. Several rail manufacturers design the little recoil lug that butt up against the cutout.
My BRM uses 4 screws. The rails they sell on the site have the 1/8 dowel holes added, so at some point they started doing it. Thanks for the reply, I guess I'll just email Borden and see what they say, maybe it's fine as is.
DaveTooley
Gold $$ Contributor
The market drives a lot of things. Consider how many various style tools there are to simply seat a primer. As Shaun said, if you have a heavy recoiling rifle with a heavy scope pinning the base is good insurance. I use 1/8 dowel pins. For most rifles 8-40 screws and a properly installed bases will suffice. Once drilled, reamed and pinned that base has to follow that action forever. When I do it I prefer to start with no holes in the base. I install the base then drill and ream for perfect alignment.
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I guess, with the proliferation of 2 1/2 pound scopes, the use of pins can be justified, even recommended. I carry my hunting rifles, so I don't have heavy scopes on them. For target rifles, I don't see the need. So, without the heavy scope, I feel ok without the pins. I even manage with 6x48 screws. WH
I had the 6- screws come loose a few times on me. I had them up sized to 8-40 and bedded the rail to the action. I was at a match and the screws had come loose which the rifle had just been at the gunsmith for a fresh barrel and I hadn't gone over it so partially my fault. After that I used JB weld to secure the rail to the action, hasn't been an issue since
Yes, that's what I'm getting at, at what point would it be considered too much recoil or too heavy of a scope? I used to run a Sightron SVSS and with rings and sunshade, it was about 54oz. How much recoil energy would be too much? 15lbs? 20? 30? What if a 40oz setup was used, would it matter at all? I don't know how to figure it out from a design/engineering standpoint and would rather not drill my receiver if I don't have to, but absolutely will if needed. It will also be shooting several thousand rounds per year.
Just glue the rail on with JB Weld, You can heat it up if it ever needs removed. My 338 Lapua knocked the screws loose on a Warne mount I had on it, When I went to the 3 ring Sako Mount it has a recoil lug on it and that solved the problem.
But I have epoxied rails on some of my rifles that are big guns like my 300 Ultra.
But I have epoxied rails on some of my rifles that are big guns like my 300 Ultra.
ELR LVR
Silver $$ Contributor
I like your style, overbuild it for the holocaust
Shoot
with all the bolts being welded to bodies, brakes being welded to barrels
why not just TIG weld the base down to the action
4 decent Tack welds at each corner
Exactly what I was thinking before I read your post.
It's a solution in search of a problem for me, as I've never had an issue. But if I did, this is what I'd do.
Retired shooter
Gold $$ Contributor
Dad used to call that. " Hell for Stout"
That's one 3/16" pin instead of two 1/8" pins. The larger pin has 2.25X the cross section of the smaller.
The incentive was to remove the pin from the front bridge. The first reason to do that is the front bridge is a busy place stress wise. After that, differential thermal expansion is the most unstoppable force on earth and there is definitely going to be a temperature gradient between the receiver and rail. One pin prevents a tug of war between two pins. The next is there are features that can't be drilled through and some care needs to be taken in its location. The R700 is the worst because the relatively short lug length and recessed bolt nose bring the threads closer to the lug faces in the receiver.
Screws the size used in rail mounts really shouldn't be used as shear pins. The screws need to provide enough clamping force that friction between the rail and receiver prevents movement. If you have a mill, it's done with larger screws and shear pins. If you don't, skip the release agent on the receiver when you bed the rail.
The reason it's done on my R700s and M110s is I start the truing process in the mill with a check of the external features with the CL I'm going to true the ID to. I check because there are some actions that just are not worth the effort. Too much misalignment between the ID, OD, and existing features. After those checks, the setup for whatever is needed for screw holes and pins is done. That's 90% of the work. Drilling and tapping a few holes after that is a relatively small incremental effort that adds significant value. The reason I haven't done it on the Magnum RPRs yet is after checking a couple of them, they don't need truing. The tenon threads and receiver face are square every time. The core of the truing process is cutting the threads and squaring the receiver face in the same setup. It appears that wasn't Remington's process for most of the M700 production so even a pretty poor lathe can do a better job.
I think an integral rail is the simplest way to cover the major sources of barrel vibration identified by Vaughn in R700 pattern receivers. Adding them after the fact is problematic though. With the tig tacks, distortion and built in residual stresses from the heating would be problems. and the only gunsmith welds I've seen that should be in the light of day were by Dan at Accutig.
ELR LVR
Silver $$ Contributor
Agreed
One reason I like to use Steel rails
to keep the expansion ratio the same as the action'
"Certain others" - tend to disagree thinking it makes no difference but, ya know how it is.
I like your analyzation of the events happening
and I would not be afraid to let my tig welds be seen in the light of day, I kinda know how
Tig welding is one method we used to repair Cast Iron with, A small tack does not heat the parent metal enough to distort,
Which with Cast Iron is the enemy causing further cracking.
going slow allowing it to cool before proceeding
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You can send it back to Jim and he will drill it for pins.
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