barrel vibrations and barrel mounted vs. reciever mounted scopes

4

404tbang

Member
Howdy!
I would like to know what differences there are on barrel vibrations, (and accuracy), if a rifle has a barrel mounted or a reciever mounted scope.

I always presumed that the reasons for reciever mounted scopes would include lighter weight and more modern design, better optics, gas filled tubes, and any of the improvements and refinements that have occured in them.

Then awhile back I started reading about modern scopes being "frozen" and getting externally adjustable mounting systems. My initial thought was, why not get an old Balvar, Unertle, Lyman sts etc. Would there be any improvements that could be made to these scopes, (gas filled tubes, better coatings on the glass), that would make it desirable to have them?

How would the barrel vibrate differently if one mount is on the barrel and the other on the front reciever ring? Vs. one on the barrel and the rear reciever ring? Vs. both mounts on the barrel?

How would it affect the barrel to reciever joint lockup according to Vaughan?

How would it affect tuning the barrel?

How would it affect rimfire vs. centerfire rifles? (should I post this in the general discussion forum as well?)

I know that shooters used to remove the recoil spring from the tube and manually pull the scope back to position for the next shot. Is this to ensure the scope is in the same position for every shot, or to get rid of the vibrations that come from the spring when the gun is fired?

Would it affect the shot if there were different amounts of spring tension in the recoil spring? In other words, could differing spring tensions be used to somewhat tune the rifle? Or is the bullet gone before the spring starts to vibrate?

Bill Calfee, and any other barrel vibration pros, could you help me understand the problems or benefits of these questions?

Thanks very much!
Greg
 
Greg, all one needs to do is visit varmit Al's web site. see if anyone wants to place a scope on a barrel after veiwing the animations. others may have a differing opinion but I say treat the top of the rifle action and barrel as you do the bottom. just my 2c.
 
I have used both types and found an improvement in accuracy on some rifles with a barrel mounted scope but haven't really seen any real problems either way. If you look at Varmint Al's site you can understand why many scopes fail at around 1000 rounds. My Unertls have been going since 1974 without any problems.

Jeff
 
Calfee

riend Greg:

Most of the old scopes you mentioned were heavy......the light ones were mounted on the action.....

Would barrel vibrations be affected by having one of those scopes mounted on the action and barrel.....probably........

But Greg, I would never mount a scope on the barrel for one reason....I'd have to drill and tap the barrel.......there's no way I'd drill and tap a killer barrel.......the drilling and tapping causes a holiday to form in the bore.......

I know it may be hard to believe but if one is careful, one can usually detect sight base holes that are drilled in the barrel when one slugs it....

Back in 93' at the BR-50 Nationals in Texas I gave a slugging demonstration using a fine Anschutz barrel.....several shooters were gathered around.....

As I pushed the slug through the bore, after cleaning it, the first thing I detected was a restriction right at the breech end...barrel was pinned too tight.....

Then as the slug went about 5 inches into the bore, I felt a restriction...I retracted the rod and measured to the point of the restriction....it was the start of the Anschutz logo stamped on the barrel...

As the slug proceeded the restirction let up....I re-measured and the let-up was just past the Anschutz logo....

I've had more than one person in my shop and slugged barrels with sight holes drilled and picked out the holes with the feel of the slug...even had customers do it..

Greg, a rifle barrel is like putty....if you touch it hard it can be injured.....

Again, I'm sure barrel vibrations would be affected somewhat by mounting a scope on the barrel.....

Hope all is well with you..

Your friend, Bill Calfee
 
Thanks Bill!

Thanks Bill!
I was hoping you would respond! Very interesting information you gave there. Your description of a rifle barrel being like putty, that could be injured if touched too hard, is perfectly backed up by the information that an Anschutz stamp could be detected by slugging the bore. I would not have thought one could feel the metal displaced by the stamp. Obviously, I am wrong. This kind of info causes one to think about things from a different perspective.

Somewhere, probably on this website, I read that someone had an Anschutz and he removed the front sight base. It shot a bit worse. Eventually, he put the sight base screws back in the barrel. He decided that the metal removed in drilling and tapping affected the choke of the barrel, especially with the screws removed. He experimented with different torque until he got the accuracy back to where it had been before. Presumably, the torque had affected the choke enough to move the metal back to where it had been before.

I have much to learn, but I am working on it. Thanks for helping further my education!


All is going fairly well. As I heard one old preacher put it, every day above ground is a good day. You were kind enough to inspire and motivate me with a phone call back in January or February. It is appreciated more than you might think. I WILL find a way to get out of the factory. Hopefully before I do too much more to my back.

Hope all is going well with you too!
Your contributions here are greatly appreciated!
Take care,
Greg
 
PS I'm afraid I've not helped you much......

If one did mount a base/scope on the barrel/action, the length of the barrel, as far as vibrations go, would be from the point of the sight base to the crown.....

The barrel in affect, would act shorter........the parallel node would be closer to the crown so the amount of muzzle device weight and position in front of the crown would be altered...

Would this alteration be a benefit? I kinda doubt it.....it may at best be a wash, with the barrel at its original length, without the scope mounted on it.....

Your friend, BC thanks Beau
 
Bill, you did help too!

Howdy Bill!
Yes, you did help too! You gave me insight on barrels that I did not have. You told me in the phone conversation last winter that wherever the barrel had contact with anything, that spot essentially became the face of the reciever as it pertained to harmonics. I have been looking at all sorts of stuff from the perspective of vibrations.

Mounting the scope with one base on the reciever and one on the barrel would seem to be a no go based on what you said. I have seen such setups on Remington 40xs. Have not had a rimfire 40x to test how that works though.

I have an Eric Johnson barrel on a Remington 37. Both of the scope mounts are on the barrel. I have a Balvar 24 barrel mounted scope on it. What little bit of shooting I have done with it, it seems to shoot pretty well. It seems to be bedded a bit long in the barrel channel. I presumed that this was necessary with the barrel mounted scope. I know Johnson experimented with different ways to deal with barrel vibration, but as I understand it, he only worked with iron sights and barrel mounted scopes.

Jeffrey, who answered earlier in this thread, said he had noted improvements in accuracy with some rifles and barrel mounted scopes.

I have an Anschutz 1413 international free rifle. It has a grooved reciever so I can shoot a modern scope. It also has mounts on the barrel for a barrel mounted scope. I have not had it out of the stock, so I do not know how, or if, it is glass bedded. When I get the chance, I want to try scoping it both ways and see if I can tell a difference. With the Balvar, I intend to try different spring tensions to see if there is any impact on accuracy. I am gonna speculate that there is no difference. But you really do not know until you try. I just know that that pesky spring vibrates. Don't know if the bullet is gone by then or not. And it's bugging me.

I see the logic and wisdom of not drilling and tapping a killer barrel after you explained it. That is another bit of knowledge to tuck away. When the time comes to get a rifle rebarreled, it won't be getting extra holes.

Getting bits and pieces of knowledge and reflecting about them can be fun and useful. Get enough bits and pieces of knowledge and experience and understanding, and a fellow might be able to notice something mundane from a different perpective.

As a matter of fact, a guy could be driving down the road in his truck and notice what the wind does to his arial radio antenna and start thinking "HEY, that's it!".......


Sincere thanks for the help Bill!
Greg
 
I have not mounted a scope with one mount on the receiver and the other on the barrel. I either mount with both mounts on the barrel or both on the receiver. I have mounted a Unertl BV 20 on the barrel block top cap and it worked really well. With a .22 rimfire you can compress the recoil spring about 1/2 way but you still have the affect of the floating rear turrets. This was a prone rifle and if they shoot in the .25 area they are usually good to go. On a benchrest type application I don't know what the affect would be.

You do have to be careful putting the mounting holes in the barrel so you don't affect the bore.

Jeff
 
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