Question on barrel length and harmonics

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Joe Stein:
The old timers used Roger Fisher's method of gaining accuracy: "
Also last thing would be to unbreach the B        lay the barrel in the spring muzzle downstream and let the evil spirits run out.  Must be at full moon on a clear night and best at midnite and better still if you visit the pow wow lady just before.... Wink"  ;) ;)

Pete G.:
Quote from: Kentucky Jeff on September 27, 2009, 11:09:12 AM

  In a perfect rifle barrel it matters not one wit where a bullet/load comes out along the curve of the waveform for accuracy purposes as it will always set up the same vibration and exit at the same point in the curve. 



..........assuming you have identical velocity from one shot to the next, which does not happen in the real world.

Artificer:
Richpiece's question and jwh1947 and FL-Flinter's replies got me to thinking why some people have no faith in bench resting a rifle, be it a ML or a modern rifle.  I fully agree that resting a long rifle close to the muzzle would induce variations you would never see when using a ML in the offhand or almost any other position.   

I've bench rested modern and ML rifles for over 30 years all over the country.  I do it to see what the rifle is capable of shooting, as best I can figuring I'm still inducing some human error variables, but not nearly as many as shooting off hand.  With ML, it helps develop the best accuracy load, though I don't file and move the sights from the bench.  That is done from shooting it offhand. 

I've seen folks rest a muzzleloader near the muzzle when they bench rest it for accuracy.  Then they complain when their groups are different and way off when they shoot it offhand.  I've shown a number of people how to more closely simulate what a rifle will shoot from offhand, by how you rest in when bench resting.  But if one doesn't closely simulate in bench resting how the rifle is held in offhand, then you won't get accurate results from the bench.

What many people don't know is a rifle can perform better or worse by the pressures you put on it when you hold it.  If you grip a forearm on a long rifle too hard with your supporting hand, it will induce pressure on the barrel that will make it shoot less accurately.  FL-Flinter's example of only a couple pounds of pressure on a barrel bending the barrel applies there.

I have to admit I was extremely skeptical of how differing pressures on the forearm and grip could cause significant differences in accuracy in a rifle.  This was until I was an Armorer on The Marine Corps Rifle Team.  We built super heavy NM M14's with heavy barrels, double lugged and torque screws, and glass bedded them into walnut stocks that were so fat only a railroad tie placed along side them made them look "sort of thin."   (These are much more like the bench rest guns used in NMLRA shooting than long rifles.)  From our super expensive machine rest, all these rifles had to shoot a 10 shot group less than 2 1/2" at 300 yards before we issued them to Team Members.   Very VERY rarely, though, the rifles "wouldn't shoot" in the hands of a shooter, though. 

When that happened, we gave the rifle to "our living machine rest" MSgt Russ Martin to shoot and test.  He would apply differing amounts of sling, hand and grip pressure and could tell you EXACTLY how to hold the rifle to shoot the best out of it.  If Russ could not get the rifle to shoot, then we completely rebuilt the rifle - even though a couple of times we put the rifle BACK on the machine rest and they shot within the 2 1/2" group size standards.

OK, so how does this apply to ML's?  When I first got involved with the International Muzzleloading Team, I passed this information along to our shooters.  Yeah, most of them thought it was "Hocus Pocus" when I first brought it up.  However, one of our better shooters got to thinking about it and realized he had tried different pressures on his ML's to get a couple rifles to shoot better in the offhand without realizing it.  After realizing it, he tried different pressures on the fore end and grip on some of his off hand rifles and sure enough, it worked the same on ML's as modern rifles.  It even helped a couple of the flintlock musket shooters. 
 

FL-Flintlock:
Artificer,

Resting the rifle near the muzzle doesn't "induce vibrations", the vibrations are induced from the trigger, lock, cap/primer (if applicable) main charge burn and movement of the projectile down the bore.  The vibrations run through the whole gun just like waves in a pan of water so vibrations induces by the lock reach the muzzle long before the projectile even starts moving and it may force the barrel above or below the nominal plane established with the barrel at assumed rest (yes, "assumed" because as stated before, everything in the environment that is above theoretical "absolute zero", 0 Kelvin/Rankine or -459.67F, does induce some level of vibration/movement in everything.  In the real world, thermal energy induction and differentials caused by sunlight, breezes and the stock should never be discounted as they are the most likely environmental conditions to cause accuracy problems within the gun.)

Back to the point - any time you place a gun on a rest be it mechanical or human, you're inserting fulcrum points.  As the vibrations and annular pressure waves pass through the length of the gun, they're going to interact with the fulcrum points and how they react depends upon the conditions of each individual shot fired.  No two rounds, no matter how carefully prepared, are ever "identical", close but not exactly the same other than by pure random chance.  

As it relates to how you rest or hold a long rifle or modern rifle, the actions and reactions related to vibration and annular pressure waves follows the same lines.  The more the stock interacts with the barrel, the more variables you're adding into the equation and removing as many variables as possible was my focus during the development of Ultra-RVC.  Just as taking a barreled action from the stock and placing it in a machine rest can completely change the level of accuracy, it does little more than prove that mechanical interaction with the stock is very much real and thus the more the stock can be isolated from the action and barrel, the less negative affect it has.  

On a full-stock, and especially a long rifle, the variables of the equation are increased exponentially purely in relation to the length of both barrel and stock.  If we look back in history, many of the shooters using cross-sticks did so with a leather sling joining sticks and being the only thing in direct contact with the rifle - the same applies to what became known as the Creedmoor style of resting the stock/barrel between the instep and ankle as opposed to using a more solid rest; whether or not it was known at the time remains debatable but in effect the purpose of both methods was to help reduce the amount of vibrations being reflected back into the gun by using a rest that absorbs vibration and annular pressure waves.

The second point that is primary to long rifles are how the annular pressure waves affect accuracy because the barrels are normally pinned to the stock in multiple places throughout the length of the barrel.  When the annular pressure waves traverse the barrel, the stock is playing a key roll in the resultant outcome of how much and to what direction/angle the muzzle moves.

Third condition that is primarily associated with a long rifle is the actual barrel length itself.  Even a "hot load" pushing a PRB well in excess of 2,000 fps still has the ball in the barrel for a long time which, of course, gives the barrel all that much more time to move around before the ball exits.  On the other hand, the fact cannot be disputed that the PRB has considerable advantages over conical bullets because of its extremely small bearing surface and the nature of the patch to respond to the changes in the bore diameter caused by the annular pressure waves.  However, the affects of annular pressure waves on have on changing the plane of the muzzle before the ball exits cannot be discounted nor can the fact that the much lower frequency produced by black powder brings the vibration frequency created by the main charge much closer to the frequency of the annular pressure waves which means they do have a higher probability of combining to create radical changes in the muzzle plane which is why you'll hear people often complain about "that one d--- flier!" that has no other plausible explanation.

How it relates to ML's is that I've bedded several half & full-stock rifles and pistols with my flexible compound with very good results.  A full-stock I had, .40 swamped percussion, refused to shoot acceptable groups bench or free hand, after bedding the groups were more than acceptable and it didn't care if it was a sand bag or human hand under the forearm but nothing is a cure-all especially if there are other issues going on.

Dphariss:
Frankly if the shooter does not take the time to learn how to shoot from the bench, not canting the rifle etc., take the time to work up a load, how to rest the rifle for best accuracy (depending on the rifle) he will not get best  results and may well think shooting from the bench is a waste of time.
MLs guns make bench shooting more difficult since moving from position between shots is the kiss of death in modern BR shooting. So ML shooters have to be very careful with positioning when getting behind the gun again after loading. Failure to do this carefully and uniformly will result in increases in group size.
If all this is done barrel harmonics will also be taken care of in mot cases.

From reading here and on other forums many shooters are not that concerned with accuracy anyway. They shoot large novelty targets at some "re-enactment" or perhaps never shoot past 50 yards at big game and if it will shoot 6" at 50 its good enough.  When with some work the same barrel may well shoot 1-2" at 100. But they don't care.
If you run dedicated rifle matches that require actually shooting well most "re-enactors" in our area will not participate. Just a fact. They don't know the history of rifle matches or the rifles used, how to shoot, care for the rifle so it will maintain it accuracy etc etc. They are, in too many cases, more concerned with how they look than how they shoot.

Dan

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