Originally Posted by dnsmith
I assumed he had already been shooting it..He did not say if he did or did not...If not then I have to agree with you on shooting it first...In fact I know of one guy that has a savage 110E I beleive in 243 cal,that has to have a pressure point at the end of the stock to make it shoot well..Without it,the **** thing shoots 4 inchs at 100 yards,with it it will do an inch easy....So that goes to show that not all barrels need to be floated..
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?
he tried several loads with out any great accracy...Once we lossened the action screes and put a few pieces of paper at the very end of the forearm and retightened the screws it came to life,with just about every load he tried in it...So floating was not the answer for his rifle..And later I glassed the end of the stock with mar-glass and now it is a great shooter...
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?
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.
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.
"Life' is tough. It's even tougher if you're stupid." ~ John Wayne
“Under certain circumstances, urgent circumstances, desperate circumstances, profanity provides a relief denied even to prayer.” —Mark Twain
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.
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.
Continuing interesting facts I wasn't aware of. Thanks for that.
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.
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.
"Life' is tough. It's even tougher if you're stupid." ~ John Wayne
“Under certain circumstances, urgent circumstances, desperate circumstances, profanity provides a relief denied even to prayer.” —Mark Twain
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.
Last edited by stangfish; 01-04-2013 at 03:56 PM.
Hey ace. I just got this Model 111 LRH 7 Mag Christmas Eve and have not fired it yet. Just alot of fondling and dry firing (with snap caps) that's when I noticed the stock touching the barrel on the left side up front. Failed the dollar bill test. Interesting you mention the pressure points sometimes being beneficial to accuracy. In fact, the Marlin XL7 guns have two pressure tabs touching the barrel and the majority of folks say their X guns are true tack drivers. Others have removed the tabs to fully free float the barrel and have seen no change in accuracy, in some cases, their groups widened. I don't know. Just seems logically to me though....if my barrel is being pressed from one side only....my results at the range will suffer.
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