sliding scope bases

[jackG]

I'm a novice shooter. I've got a Marlin mod 60, SS. I had a scope mounted and after firing a couple of mags of ammo, the scope bases creep back and if not monitored and tightened relentlessly, they will slide clear of the rails in the rear. It sound rediculous but nevertheless, that's what is happening.

I tried tightening the screw after every magazine and about the time I think it has seated in, off it comes again. I talked to the guys at SWH. They said it's not unheard of with that rifle. They suggested it is caused by the bolt slapped to the rear when fired, producing a hammer effect, plus the characteristics of the SS in the receiver. They recommended using some lock tight on the bases, which I've done. It's curing right now.

Has anyone here had that problem and if so found a cure? If the lock tight won't hold them, what might be an option?

The rifle scope otherwise perform acceptably for a classic plinker, producing 1.5" groups, 3/4 of which are in the bull, at 50 yards. That is, when the scope isn't sliding off the rails. Trust me. That produces a higher point of aim!

[ken w.]

You may want to invest in a BLK mount.This will prevent this.This mount will clamp much tighter than the regular rings.You could put a drop of clear nail polish on the dovetail and then reclamp your rings down and let it harden and see if this will work.

[rangerruck]

you have three choices here, either get very wide scopemounts/rings, the kind with 4 screw holes through the top. these are wider at the base also, and gives it a larger friction/grip area. the bkl scope mounts, mentioned above, are very stable on dovetail rails. Kwiksite makes weaver tip off blocks, they look like little leggos. put those on first, then put on an appropriate set of rings, that will fit on the tip off blocks. All done.

[stash247]

Jack, not knowing what scope rings you are using puts me at some disadvantage, as does my lack of knowledge about semi autos, but if the rings are sliding to the rear, they are moving as the bolt 'slaps' into battery, moving itself, and a fresh round, forward!
This a common cause for rifle scope failure, when used on a spring piston air rifle, which also has a 'forward recoil, exactly the opposite of what a rifle scope was built to withstand!
If the M-60 has an integral dovetail, which I will assume it does, look at the 'adaptor' mounts offered by Weaver( TO-10, TO-13 come to mind, drill the center of the integral dovetail, with a little 'divot' for the setscrews that secure the Weaver Base, and use Weaver rtings; they have a crossbolt, riding in a slot, in the base, that will NOT allow movement!!!
I have put well over a thousand rounds thru a 6 1/2 pound, scoped, .375 H&H Mag (TCR 83), and have yet to lose zero, except in changing loads.
This is more abuse than a rimfire rifle could offer, shot daily, a brick a day, for 50 years!
I am kinda partial to them ugly Weaver bases, I guess, because they, like the old Steel Tube, El Paso Weaver scopes, have served me well for over 40 years, without a single failure!
I owned a Jaguar Automobile, long ago, and sold it for less than it was probably worth, because I wanted to drive, not concentrate on Maintainance.
That is why I reccommend Weaver, old, and new.
Best of luck, with your problem, and let us know what works out!

[LDBennett]

JackG:

Every scope mount needs a recoil stop. When you use Weaver style mounts the rail is machined so that the cross bolt on the scope mount passes through that machined cross slot area and rearward motion is stopped by the shank of the bolt, that tightens the scope mount to the bases, hitting the machined slot in the Weaver base.Other mounts incorporate some protrusion on the bottom of the scope mount that rides against a slot in the mount.

If the mount for the receiver attaches to the receiver via screws one of the screws can be made longer and include a small bushing to raise the top of the screw so that it can operate as a stop. The stop needs to be located so as to move the scope mounts and scope with the gun in recoil. The scope wants to stay in place in space while the gun wants to move to the rear. The stop screw has to be positioned so as to carry the scope along with the gun in recoil. Sometimes the positions of the screws for mounting the base do not end up anywhere close to the right place and you have to abandone the mount and go to a Weaver style with the cross machined slots.

In general any mount system for a scope, regardless of the recoil level, needs a recoil stop of some kind.

LDBennett

[stash247]

LD, if I read the original post correctly, his scope is sliding off to the rear, not the front, which I would expect with cheap mounts on a heavy recoiling rifle; this is, as I mentioned, the nature of a 'spring piston' air rifle, with the mass of the piston going forward, to a sudden stop.
Something's not quite here.
Sako, and Tikka, use trapezoidal, Integral Bases, smaller at the rear, and every shot hammers the scope tighter onto the rifle, because thr rifle recoils (to the rear) and wedges itself more tightly into the rings, with every shot; Jack G's scope is going in the wrong direction!
Your solution mirrored mine, ampllifies it, really, but why is the scope moving to thr REAR???

[LDBennett]

Stash247:

Cheap rings may tighten on themselves and not on the rail. I haven't used any of those cheap rings in years and forgot how bad they were until you mentioned that they might be cheap rings. Also all rails are not created equal...some wider than standard , some narrower. I hate cheap scope mounting systems!

It is so hard sometimes to solve these "problems" remote control. It would be so much easier if the gun were in my hands and I could inspect it and run a few simple tests. Add to that, its what they don't tell you up front that usually helps solve the problem.

LDBennett

[stash247]

LD, you said a mouthful!
There are times when I don't use Weaver rings and bases, but there's got to be a darned good reason; wonder why the military Picatinny Rail is dimensionally identical?
I own several rifles which wear optics that exceed the cost of the rifle, because I cannot hit what I cannot see!
Several years ago,in New Mexico, four of us were on a seven day Mule Deer season, at around 7,000 feet, in snowy weather. Larry, the Engineering Director of a large, nationall known and respected research firm, was hunting a 'Custom Shop' Remington 700, and immediately began to make jokes about my iron sighted, 40 Sharps BN, Sharps rifle; it was a single shot, black powder caliber rifle, we weren't hunting buffalo, ad nauseum.
18 hours later, he picked up his rifle from in the Motorhome, stepped outside, then back in; "****! My damned scope is all fogged up!"
High dollar rifle, cheap Wally World scope, and a 70* change in temps will darn sure queer a hunt, especially, if you only brought ONE rifle!
He hunted the rest of the week with my spare rifle, a .375 Bolt gun, under a steel tube, El Paso Weaver, in Weaver mounts.
That package is so consistant the scope turret caps have the same grease sealing them they had in 1988.
He now knows why I feel as I do about cheap gear, scopes included.
Back to the thread, directly, if you are gonna scope a rifle, it "only costs a nickle more, to go first class".

[LDBennett]

Stash247:

I would think storing the gun outside for a few hours would have cleared up the fogging. Of course, you'd have to leave it outside for the fogging not to come back. Isn't that the way it works? I shoot and have regularly for the past 20 years but I don't hunt (you know Bambi and all that stuff) but I applaud those that do hunt so I don't know about bad weather shooting at all.

I used to buy only Leoplod, Burris and a few of the other well know more expensive brands but when the prices nearly doubled over the last 20 years I down scaled to the more affordable models. My favorite scope today would be the Bushnell Trophy series, usually the 4 to12 or the 6 to18. My old eyes are so bad anymore that a hour or two on the scope has them doing the blurr thing so bad that shooting is a waste of good ammo. I know optics (camera collector/user) but I can not see the difference between the Bushnell Trophy scopes and some of my older Leopold and Burris scopes and a couple of the Burris's have developed a tightness in their optical adjustments that have me believing that maybe the extra cost of the Burris' was not worth it. Anyway, I won't use any of the bottom feeder scopes. I don't buy any scope that cost less than $150 or more than $300 with the emphasis toward the $150 scopes. That still allows the Weavers and several other well know name brands but I cringe at the thought of Tasco's, Simmons, BSA, Carabela, etc. You get the idea.

LDBennett

[stash247]

I already had it (the idea).
I can't rmember ever buying a new scope, except for two vintage Unertl's, from and estate auction (at about 40% of their 'then' value), and a Supertargetspot Lyman, the same way; all of these scopes were 30 years old, or more, when I bought them!
Much of this list is too young to remember Weaver, when the scopes were blued steel, made in El Paso, Tx; I wish I were so cursed (lol).
They were and are pretty plain looking, but offered the rifleman durability equal to, and in some conditions, exceeding Leupold, Redfield, or Bausch and Lomb.
I have never shot a recticle or lens loose in an old Weaver, and I have them mounted on some serious caliber, ultra light weight rifles!
I prefer the 'picket post' recticle, for hunting, as it gives me an hour more daylight, half on each end of the day, that I can see to shoot.
And, I typically buy them, at gun shows, pawn shops, etc, for forty to sixty bucks, which makes the monetarily 'more affordable than that BSA, or Tasco, as well. Hell, I've bought rifles, if priced right, for a scope, rings, maybe even the base, then sold the rifle, at a profit!
How cheap does THAT make good glass???
I will not tolerate a rifle, or a dog, I cannot trust. Where rifles are concerned, conditions may change, but the 'zero' must not.
And a scope that fogs, regardless of weather, is junk!
On a different note, kinda 'cross-posting' from Gen Discussion, my little Red heeler is here at my feet, (just got back from a Spurs/ Pistons game), wagging her tail, wanting to go to bed.
We've been two full weeks, in a busy garage, on one of the busiest intersections in San Antonio, without an issue, of any sort! She has been on a leash about 1/2 hour of that time, when we were at Dr Becker's (My Vet), because that is his policy; one end on her collar, the other, in her mouth.
Yeah, he chewed my ass, but I trust her that much.
Forget price- THAT's what I demand in a scope!