The luxury of a stopped muzzle.

Bill Calfee

Gun Fool
The luxury of a stopped muzzle.


CYA friends:

Why did I just use the word "luxury" in the title of this thread?


I used the word "luxury", because a RFBR gun having a true "stopped muzzle" is most certainly a luxury, simply because the muzzles of most RFBR guns are not stopped.


You read that correctly, most RFBR guns do not have stopped muzzles.



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One of the reasons most RFBR guns do not have their muzzles stopped, is because it is impossible to stop the muzzle of a gun that is not capable of having its muzzle stopped.



Very few RFBr guns today are capable of having their muzzles stopped, for a variety of reasons.


(And as long as there's so much goofy tuning nonsense floating around the Internet, that ain't about to change any time soon.)



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Exactly what does it mean to have the muzzle stopped?


I've probably said this a thousand times over the years, but:


When the "exact center" of the "parallel node" is moved to the exit of the crown, by a properly weighted and positioned MD, the muzzle becomes stopped.

And when I use the word "stopped", that's exactly what it means......the muzzle is completely motionless.



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CYA friends, what confuses the masses about a stopped muzzle, is the fact that the "parallel node" has length.....


And as long as every round you fire stays within the length of the parallel node, as it leaves the muzzle, accuracy will be exactly the same as if the muzzle is actually stopped, even if the "exact center" of the parallel node isn't at the exit of the crown.


I'm going to stop here, for now.....I'm headed back to the range.


Having a stopped muzzle is most certainly a luxury.......because there's so few RFBR guns that have their muzzles stopped, for a multitude of reasons.

( The biggest reason is that most of them aren't capable of having their muzzles stopped)




Your friend, Bill Calfee
 
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The luxury of a stopped muzzle...

The luxury of a stopped muzzle...


CYA friends:


If your gun has the muzzle stopped, then the only vertical at the target, is that caused by the velocity variation of the ammo.

I'm talking about shooting in perfect conditions of course......indoors for example.



With the very best ammo shot in a Class A RFBR gun with a stopped muzzle, that vertical caused by the velocity variation of the ammo is about .150" at 50 yards.



There has never been a World Record target fired in history, that doesn't show this .150" of vertical......not a single target, ever.


(By the way, this is why that goofy compensation nonsense is, well, goofy.)

If that goofy compensation nonsense were a fact, then the .150" of velocity variation induced vertical would be removed.

But that is impossible.



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When the muzzle is not stopped, we wind up with a double whammy.......


We not only have the .150" of velocity variation of the ammo to deal with, we also have to deal with a flopping muzzle.



CYA friends, if every shooter could fully understand what I'm about to say next, all of those goofy tuning theories would disappear.



1. A muzzle is stopped when the exact center of the "parallel node" is located at the exit of the crown.

2. And once you get the exact center of the parallel node to the exit of the crown, it stays there forever.

3. The "parallel node" has length, and this length does change depending on the severity of the barrel vibrations.


4. But one more time, the exact center of the parallel node does not change.....it is stationary, always, no matter whether it's at the exit of the crown or not.


5. On a naked barrel for instance, where ever the "exact center" of the parallel node is located, which is dictated by the stiffness of the barrel, it stays there, never moving.

I've added an edit here:


My comment in #5 above....the stiffer the barrel, the closer the exact center of the parallel node is to the muzzle....which is why benchrest shooting, using naked barrels, gravitated to bull barrels over the years.



6. Therefore, as long as every round leaving the muzzle, leaves within the length of the "parallel node", then accuracy will be just as good as if the muzzle were actually stopped.




7. Here's the most important part of this whole thing, and once it's understood, will shed light on every "tuning ailment" folks find themselves having to deal with:



When your muzzle is not stopped, but your MD is set close enough so you're working withing the length of the parallel node, if you have a round with just enough excessive velocity to move that round outside of the length of the parallel node, that round receives that double whammy......you have the vertical induced by the velocity variation of that round, plus, that round is leaving a flopping muzzle.


Please take time to read the above paragraph several times.


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Here's the difference between working with a stopped muzzle, or working within the length of the parallel node without the muzzle fully stopped:


That excessive velocity round I just spoke of, if it had left a stopped muzzle, with the only vertical at the target caused by the excess velocity, that round may still have wound up as a plugged ARA 100, or plugged IR-50 10.....

But since that round had to deal with the "double whammy", of the velocity variation plus the muzzle flopping, it might wind up as an ARA 25 or an IR-50 9, or even an 8.



This is the luxury of a stopped muzzle.


Your friend, BC


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PS:

CYA friends, I will bet anyone that no more than 1-in-5, 20%, of the RFBR guns in the world have their muzzles stopped.

There's several reasons for this, the main one being that very, very few RFBR guns are capable of having their muzzles stopped.
 
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How does this apply

How does this apply


CYA friends:


How does all this stopped muzzle and parallel node length stuff apply to everyday "tuning headaches"?



A Class A RFBR gun will produce excellent accuracy, without the muzzle being truly stopped, so long as the MD is set close enough to allow the ammo to stay within the working length of the parallel node.

Once again, the "exact center" of the parallel node never changes its position on the barrel, this is why once the muzzle is fully stopped, it's stopped forever.


But, the parallel node, itself, does change in length, equally, both in front and behind its "exact center", depending on the severity of the muzzle oscillations.


OK, applying this to a real world "tuning headache":


Waxed, lead bullet ammo is affected by the environment in which it resides.........higher humidity causing more condensate in the bore, etc.


Say you have your MD weighted and adjusted so you're within the working length of the parallel node, but the muzzle is not stopped.


So you shoot a card and kick out a 2350......


Then the next day you shoot another card, with the same ammo, and it just "wallers", as Rick Shouse calls it.


What happened?


Obviously shooting conditions, could, cause this issue......


But most of the time here's what has actually happened:


Since you don't have the muzzle fully stopped, under the environment your ammo was in when you kicked out the 2350, maybe only a round or two stepped outside of the parallel node, and received the "double whammy" of the vertical induced at the target caused by the velocity variation of the ammo, plus a flopping muzzle.


The next day the environment the ammo was in may have produced more condensate in the bore, for example, causing maybe 20% of the rounds to step outside of the parallel node.......so the ammo just wallered.


CYA friends, if your muzzle had been fully stopped, you would not have seen such a drastic difference between the two days of shooting, or maybe any difference at all.




And one other thing here.....which can give a completely false picture of how a MD works.

Say as the shooter starts shooting on that second day, and finding the ammo wallering, they reach up and turn the MD, and get lucky and turn it in the correct direction to move the ammo back into the length of the parallel node, and the ammo goes back to shooting again.


That shooter immediately develops the mind set, that a MD needs to be adjusted for various shooting conditions.


No it does not................not if the muzzle is stopped.


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CYA friends, when one understands the physical laws of how a gun barrel vibrates when fired, and how a MD works, there's not a quote, "tuning issue problem", that doesn't have an explanation.



Your friend, BC
 
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The luxury of a stopped muzzle

The luxury of a stopped muzzle




CYA friends:


The greatest example of "the luxury of a stopped muzzle" has to be Wiley and Janet Westfall.


I built them a RFBR gun back in the 90's.......

I tested the build, set the MD and shipped it to them.


Over the next ten years those two won countless State, Regional, National Championships, and set World Records with that build.

No telling how many different lots of ammo passed through that rifle during those ten years.


I got a call from Wiley one day saying the Lilja on their build had finally laid down, and would I re-barrel it....I said, "of course".


So Wiley shipped me the rifle.......


The MD had an old, yellowed piece of duct tape wrapped around the adjustment readings, and, I couldn't get it off the barrel.

I finally had to make a tool to slip over the barrel and drive the MD off, the aluminum MD had oxidized to the steel barrel.


So I called Wiley and asked him when was the last time he had the MD off the barrel?

He told me he had never had the MD off the barrel in the ten years he owned the rifle, and he had never moved the MD a single click of adjustment from the way I had shipped it ten years earlier........that's why he had the masking tape around the MD.


This is the luxury of a stopped muzzle.
 
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