I've read that the most consistent reason for scopes to shift are the attchement between the mounts and receiver. Are the factory screw holes adequate or do you do something else to make the attachment stronger? I know Kimber is using bigger screws and I've heard of others JB Weld to attach the mounts. I'm plannig on using Weaver style bases on a M700 and woud like the best attachement I can get. I figure if the mounts were permanently attached I'd have some flexibility on rings with the Weaver bases. Any input appreciated

The factory holes are generally sufficient unless you plan on abusing the gun in which case you can have the existing holes retapped to 8x40 which provides considerable grip over the factory 6x48. I don't know if I would get too carried away using JB weld, but you are more than welcome to do it. Just remember, at some point you may have to remove them... Good luck!

I don’t permanently attach bases but I do “bed†them to the receiver with Devcon to assure that they mate perfectly with the receiver, and I normally resize to 8x40 screws if the base[s] allow it. Since all receivers have slight variances in their radius, and so do scope bases, the chances of having the two match perfectly are not real good.

Rick & malm, how do ya'll go about resizing to 8x40 screw size? do you have to have a jig/drill press to do the job, or will opening them up to the right hole size with a hand drill let the drill self center in the existing tapped hole. Also, if it's doable with a hand drill, is a regular HSS drill bit and 'normal' (sears or equal) tap sufficient?

Thanks--Don

quote:

Originally posted by Fish30114:
Rick & malm, how do ya'll go about resizing to 8x40 screw size? do you have to have a jig/drill press to do the job, or will opening them up to the right hole size with a hand drill let the drill self center in the existing tapped hole. Also, if it's doable with a hand drill, is a regular HSS drill bit and 'normal' (sears or equal) tap sufficient

Thanks--Don

If you want them drilled and tapped straight and square you should use the proper tools, and hand drills and hand tapping without guide bushings/jigs ain’t a real good idea unless you are a hell of allot more talented that most of us out there. Personally, I use a Forster Universal sight tool mainly because I own one, and its already set up to quickly mount to my drill press table...but other set-ups can work just as well.

quote:

Originally posted by Rick 0311:

quote:

Originally posted by Fish30114:
Rick & malm, how do ya'll go about resizing to 8x40 screw size? do you have to have a jig/drill press to do the job, or will opening them up to the right hole size with a hand drill let the drill self center in the existing tapped hole. Also, if it's doable with a hand drill, is a regular HSS drill bit and 'normal' (sears or equal) tap sufficient

Thanks--Don

If you want them drilled and tapped straight and square you should use the proper tools, and hand drills and hand tapping without guide bushings/jigs ain’t a real good idea unless you are a hell of allot more talented that most of us out there. Personally, I use a Forster Universal sight tool mainly because I own one, and its already set up to quickly mount to my drill press table...but other set-ups can work just as well.

Second that!

While it seems awful tempting to use a hand drill and tap, it's REAL EASY to screw up a hole and break a tap without some type of guide. Unfortunately I don't have the Forster fixture so I'm stuck using my milling machine to drill and tap, which does make it pretty convenient for those times when I encounter holes that are a touch off track and need correcting, or, when I myself break a tap and have to remove it.

I like the Forster tool for its ease of use...and I bulit a fixture for it that lets me index right off the holes in the base[s] I’m using so that speeds things up also.

When set up properly it lets me know right away if an existing hole is off center or drilled and tapped crooked so I can fix it.

The only problem I had with it was having to make up some Jig-Barrels to use if I’m drilling and tapping just a receiver, so now I have a bunch of 1 ¼ “ round stock threaded to fit different receivers laying around.

quote:

Originally posted by JAB:
I've read that the most consistent reason for scopes to shift are the attchement between the mounts and receiver. Are the factory screw holes adequate or do you do something else to make the attachment stronger? I know Kimber is using bigger screws and I've heard of others JB Weld to attach the mounts. I'm plannig on using Weaver style bases on a M700 and woud like the best attachement I can get. I figure if the mounts were permanently attached I'd have some flexibility on rings with the Weaver bases. Any input appreciated

Any input, huh.

I have an M700, 8x40 mount holes, a Badger Ordnance M24 long action 1 piece 1913 rail, and a pair of Badger USMC SASR rings. No Devcon, no JB weld. BULLETPROOF.

Anyhow, definately take the gun to a smith to get the holes drilled, unless you have the proper tools to do it. Tearin up stuff sucks when you have to pay the smith to fix your screw up, then do the job you were trying to do in the first place.

BTW some folks might add that one piece bases are better than 2 piece as far as security and how the rest of the package lines up with the bore, and how much your rings will need to be lapped for 100% contact to scope.

Rick and Malm, I appreciate the feedback, I have more than just basic tools in my shop, including a drill press, no lathe though. I also don't have any action/barrel jigs or fixtures. I have worked on a lot of archery equipment, and have enlarged holes from 6x48 to 8x40, and when using a drill or drill press the existing hole would self center the drill bit and/or tap. The materials would typically be aluminum though--occasionally magnesium, so that is what led me to ask. The steel in rifle actions is certainly harder, so I'm trying to figure how to skin that cat. I'll poke around in my Brownells and see what they have that might help......What's involved in reworking bases for talley mounts--do you have to buy new bases, or will the shoulder of the 8x40 screw fit in the 6x48 hole?

Thanks guys--Don

PS--I've broken 2 or 3 taps in my time, I don't want to have to fool with that again. What a PITA

Don,

Drill bits “self-centering†can be exactly what you don’t want to happen, especially if the original holes aren’t perfectly lined up and square...or if your set up isn’t level and square.

If you want to do this without using guide bushings I would suggest using graduated bits or chucking reamers to gradually open up the holes for the 8x40 taps rather than just running a number 28 drill bit through the existing holes. Chuck the bits where there is no more sticking out than you need, because you don’t want the bit flexing on you.

Either way you are going to have to have some sort of set up that allows you to level and hold the action firmly in place and square to the drill press quill/chuck. I would also stick the bit in your drill press and check the bit and the chuck with a dial indicator with the machine running to see how much “slop†you have. Jacobs chucks are not the best at holding and keeping really small drill bits square and centered.

I’m not trying to scare you off...only trying to help you avoid screwing up your project. I know guys who have just used the scope bases as guides and it worked out okay for them...but you have to be careful and make sure of your set up before you start running that drill bit in there...metal is hard to put back once its removed!

quote:

Originally posted by Fish30114:
What's involved in reworking bases for talley mounts--do you have to buy new bases, or will the shoulder of the 8x40 screw fit in the 6x48 hole?

You won't need new bases, just open up the existing holes to accept the 8x40 screws.

Rick, good info, I hadn't thought about the slop in my drill press, it's just a delta rig from back in the day when they were thought to make OK stuff---It sounds like I'm just under equipped, I need to see if a really nice press vice might be available, that might get me close..... I am only aware of a few smiths in the area, and when I called 2 of the 3, they said they would just use a regular old drill press, and some jigs they had, that wasn't real reassuring--I've got about 28 rigs, and if I change, I want to do them all.....otherwise I might send them all to malm.

malm, thanks, I was hoping I just had to open up and retap the holes and the bases would be OK, I'll call Talley and get a bunch of the right size screw in 8x40 if I decide to give this a go.

Appreciate ya'lls help--Don

Brownells sells a kit that has the right bits, taps and countersinks to convert to 8-40 base screws. Also has a selection of screws and a gizzy to shorten screws.

Personally, I use screws with the same head as my Leupold rings, so one size of wrench fits both.

Seems like the kit is called a "Tactical base screw kit" or some such.

McCray, good tip, I've got my Brownells catalog out just now.

Thanks--Don

I have always glued the bases in place using AcraGlass as I was installing the screws. The few times I had to remove a base I had to tap it with a hammer after removing the screws. This has worked for me on rifles as heavy recoiling as a 450 Ackley that only weighed about 8 pounds.