Stock is Touching Barrel on Brand New Savage...Problem?

[Roger SS]

Just wondering out loud and not meaning to hijack the thread but.... This pressure point is acting as a vibration dampener to reduce the whipping action at the end of the barrel. Mass(material density being a factor) and length of the unsupported barrel effect its natural vibration frequency as well as amplitude, basicaly all that determines how much a barrel can whip or move and at what frequency it will be moving. The exciting force being sufficient to generate harmonics is the detonation of the round and the wave of vibration moving down the barrel towards the mzzle end. So enter the pressure point to reduce the movement of the barrel by shortening the unsuported length of the barrel you have reduced the amplitude but increased the frequency. This is effective I have seen it.

So my question is, in this situation would a different load be the solution rather than a pressure point? Is the design of the barrel i.e... diameter, length and or material wrong?

Very interesting study in physics. Am I to conclude that you believe having pressure points on the barrel is more desirable to increase accuracy instead of a free floated barrel?

[J.Baker]

What an interesting idea. Thank you. I know you said it worked fine for you. My concern would be putting the fore end of the stock in boiling hot water....does it have any unwanted effects like possibly ''warping'' the overall integrity of the stock? I guess what I'm asking is, does it effect the outer part of the stock or cause swelling after it cools?

Ever seen how plastic parts are made? It's called an injection mold press - small plastic pellets are heated and melted into a liquid state and injected into the mold under high pressure, then the mold rapidly absorbs the heat from the plastic which allows it to cool and solidify. Re-heating the plastic isn't going to affect it's integrity in any way shape or form. Depending on the mold and complexity of the part, an IM press can kick out a part ever few seconds (plastic forks) to one ever 15-20 seconds (Ford HVAC housing) to one every minute or so (old tube-type TV housing). Also, in many cases said molds are multi-cavity so they produce multiple parts each time the press cycles.


Very interesting study in physics. Am I to conclude that you believe having pressure points on the barrel is more desirable to increase accuracy instead of a free floated barrel?

Not a new idea at all. In fact, if you look at many older sporter-weight rifles (1960's and older) the factory would intentionally put pressure on the barrel with the stock - usually at the very end of the barrel channel. It would just be a little bump in the wood that would serve to shorten the harmonic wave length of the barrel. It wasn't until the mid-late 60's that free-floating barrels became a popular practice. The practice isn't completely forgotten in modern times either. Sim's Vibration Laboratory (SVL) makes a rubber donut you can slip over you barrel and move forward or back to "tune" the harmonics. More elaborate and expensive harmonic barrel tuner's are still quite popular with some old-school rimfire competitiors as well.

[stangfish]

Very interesting study in physics. Am I to conclude that you believe having pressure points on the barrel is more desirable to increase accuracy instead of a free floated barrel?

Roger, I was simply stating that however unintentional, the barrel that needs a presure point is tuned to a frequency that that particular cartridge excites. Like tuning a guitar, when the string is tuned it vibrates in sink with the body of the guitar and it resonates. That is the harmonics. When this particular phenomena takes blace the only thing you can do is increase mass or change the unsuported length so you can take the barrel "out of tune". Food for thought.

[thomae]

It appears to me that one can "tune" a barrel for a particular load, or conversely, come up with a specific load "tuned" for the barrel.

Two different ways to gain accuracy.

[RevM]

It appears to me that one can "tune" a barrel for a particular load, or conversely, come up with a specific load "tuned" for the barrel.

Two different ways to gain accuracy.

Yep. It's simple rocket science (ie, physics). However, the contact from a marginally molded stock touching only one side of the barrel in some random spot is likely to create problems that vary with temperature (summer to winter ... or hot to cold barrel). A carefully placed contact node dampener or two could be applied at just the right spot(s) to kill the natural vibrations of the barrel and would be less prone to variability due to expansion and contraction with temperature.

[Roger SS]

Yep. It's simple rocket science (ie, physics). However, the contact from a marginally molded stock touching only one side of the barrel in some random spot is likely to create problems that vary with temperature (summer to winter ... or hot to cold barrel). A carefully placed contact node dampener or two could be applied at just the right spot(s) to kill the natural vibrations of the barrel and would be less prone to variability due to expansion and contraction with temperature.

Continuing interesting facts I wasn't aware of. Thanks for that.

[stangfish]

Very interesting study in physics. Am I to conclude that you believe having pressure points on the barrel is more desirable to increase accuracy instead of a free floated barrel?

Only if necessary and usually on a thin barrel but not always. Again mass and length have an effect on resonance of a vibration frequency. Every barrel has a natural frequency like a guitar string. If you excity that frequency the amplitude with be at its greatist. A presure point is like muting the guitar string. It no longer "sings.

[J.Baker]

It appears to me that one can "tune" a barrel for a particular load, or conversely, come up with a specific load "tuned" for the barrel.

Two different ways to gain accuracy.

Correct, and it's much easier to tune the load as you have direct control over it's qualities when handloading. Trying to tune a given barrel to a given load would just be an exercise in futility.

[missed]

My new 10FLCP-k fails the dollar bill test too, it will be getting some sand paper tonight hopefully!

[Westcliffe01]

Yes, this is the point exactly. The last thing one wants is any kind of intermittent contact. The pressure point at the front of the fore end is a woefully inadequate solution. All one needs is for the wood to expand or contract or for a polymer stock to be stiffer or more limp due to ambient temperature, then any concept of uniform pressure or damping being applied to the barrel is out of the window. If you do own a rifle like that, you need to be very certain of your zero under the conditions you are going to hunt. Or simply free float it and add a rubber damper donut to the barrel. You will then have to find the right position for the damper.

The whole point of free floating the barrel is that the harmonic behavior would be dependent primarily on the barrel material, geometry and the load characteristics, with the load characteristics being the most easily manipulated.


Yep. It's simple rocket science (ie, physics). However, the contact from a marginally molded stock touching only one side of the barrel in some random spot is likely to create problems that vary with temperature (summer to winter ... or hot to cold barrel). A carefully placed contact node dampener or two could be applied at just the right spot(s) to kill the natural vibrations of the barrel and would be less prone to variability due to expansion and contraction with temperature.

[missed]

I fixed my stock, but now can't get the bolt to close and work correctly now!!!

[Westcliffe01]

Action screw is probably a bit too long (loosen the front one a bit). If that fixes it, grind a bit off the end of the screw, probably a bit more than 1 turn on the thread.

[missed]

Action screw is probably a bit too long (loosen the front one a bit). If that fixes it, grind a bit off the end of the screw, probably a bit more than 1 turn on the thread.

That didn't do it, I took the screw all the way out.

[Westcliffe01]

OK, did you do anything with the scope base then ? That can foul the bolt from the top instead of the action screws from the bottom. Perhaps check where the back action screw goes, it case it could also foul. Those are about the only things that can get in the way of the bolt.

[missed]

OK, did you do anything with the scope base then ? That can foul the bolt from the top instead of the action screws from the bottom. Perhaps check where the back action screw goes, it case it could also foul. Those are about the only things that can get in the way of the bolt.

Actually I did torque the base bolts, I'll go check that!

[missed]

Dang my luck second screw from the front was causing the problem! And the front screw is broke off flush!

Thanks guys!

[fla9-40]

I found this site's opinion very interesting on this subject, and since then have found other long range shooter sites that agree with him:

http://www.larrywillis.com/tip021.html

[cfvickers]

nevermind.

[MZ5]

I am shocked, SHOCKED!, to find that Savage's production process allows such ridiculous variability rifle-to-rifle. Oh, wait, no I'm not. I've been victimized by it too many times myself...

To the point about barrel pre-load (the contact points purposely installed in the forend on some other brands): It's about applying a preload moment to the bbl-to-receiver joint. This screw joint is surprisingly flexible, and a preload moment has been shown to be significantly effective at reducing dispersion. See Harold Vaughn's book, Rifle Accuracy Facts, for instrumented testing on the topic.

The difficulty with the strategy, and the reason free-floating became popular, is that getting the preload right consistently is challenging in a low-cost mass-production shop. The present thread about Savage's production variability demonstrates this well.

Also, wood warps sometimes which messes the preload up, and the AMAZINGLY cheap plastics used in most of today's rifles isn't that well suited to the task. Thus, it's simply cheaper and easier to free-float 'em. ...and then there's the percentage of production that's supposed to be free-floated but isn't, that gets sent out the door anyway...

[Westcliffe01]

If you get a 10PC (mine was only $550 in 223) with the accustock, these kinds of things don't happen. But with regular (wood/laminate/plastic) stocks, every one I have had has needed work. Usually never more than a couple of days worth of fiddling before they behave themselves. I no longer buy anything with a sporter barrel, unless the price is better than just getting an action.