Barrel Contour vs Accuracy

[BartsBullets]

So for us mere mortals, where did we settle on this? The heavier the contour the better for accuracy?

Mike,

From my perspective there’s a lot more that goes into barrel that makes it shoot then it’s contour. Not throwing credentials but I have shot World Records with straight 1.450 barrels, HV contoured barrels as well as LV barrels. I think most of this post is due to cabin fever and theoretical BS!

To the OP and his orginal post I’d get the heaviest contour the rifle can stand and go from there.

Bart

 

[gunsandgunsmithing]

Now that he's quoting barrel times I'm seeing some divergence Ohh Well )

A

What!!?!! Now ya being foolish!

 

[Phil3]

Mike,

From my perspective there’s a lot more that goes into barrel that makes it shoot then it’s contour. Not throwing credentials but I have shot World Records with straight 1.450 barrels, HV contoured barrels as well as LV barrels. I think most of this post is due to cabin fever and theoretical BS!

To the OP and his orginal post I’d get the heaviest contour the rifle can stand and go from there.

Bart

Yep, looking at a Varmint Match #9. 6.5 lb. weight should also help minimize recoil.

 

[Alex Wheeler]

Al,
I do not disagree with your support of Mike, and Im not backing Bart. Thats not how I took your post. But if you think Im just out to be friendly and have not proven any of my ideas I have to strongly disagree with you on that. Advancing the sport does not happen on the internet as you know. If you have good ideas and they work, someone with take them up and put them into production, you dont have to be friendly you just have to prove them. Usually that requires being unfriendly, at least at first. And by the way, I would like it if you could make it to a match out this way. Im always up for heated discussion and its better in person.

 

[Bart B.]

And furthermore I said that Bart B was engaged in a technique I call "baffling them with bullshit" and that he was incapable of "making himself more clear" because he didn't have the facility. And furthermore that quoting Geoff Kolbe's opinions do nothing to further his agenda.....

The answer to this part is quite simple..... for BART B to step up and show me wrong. Of course he didn't and couldn't and won't....he went on to tell as how "we got to the moon via computer modeling"

again I say..... SERIOUSLY??

I'm glad you find a kindred spirit in Bart B but that just ain't what I'm about. This is a public forum. I'd rather be W R O N G and shown to be wrong than to be spewing untruth. And BTST I dislike it when opinion is sold as "truth" because I've spent tens of thousands of hard-earned dollars testing other people's opinions, believing "The Experts".... Only to find out they're just goobers like me.

Of course, you feel better bad fingering me on your keyboard instead of asking for an explanation you might understand.

Whatever. Have a good day in spite of your limitations.

 

[alinwa]

Just a cautionary note -- like many physics "calculations" this is more of an estimate than a to-the-millisecond take-it-to-the-bank number. I assumed that the gas escaping from the muzzle is traveling at the same velocity as the bullet (gas is really traveling faster), that the bullet accelerates uniformly in the bore, that the rifle recoils without friction, etc.

At any rate, with typical bullet weights, powder charges, rifle weights, barrel lengths, and resistance to recoil (friction, shouldering, etc.) the rifle is moving a small fraction of an inch (not multiple inches) while the bullet is in the barrel.

Hey Toby.... glad to see you're still willing to seat-of-the-pants it my man

Be SWAGgin', our Toby........

So, because I find barrel time to be fascinating. And because I don't believe a man can shoot well until he TRULY BELIEVES that "it all happens AFTER you pull the trigger!!"

I'll opine some more about recoil and barrel time, against my better judgement but "In for a penny" and all that....

I use the description "a quarter inch for BR rifles, 1/2 inch for hunting guns" as my baseline for passing on my ideas re how to avoid steering the gun.

I believe the true "safe" to be more like 1/10" for 6PPC BR rifles, 1/8" for something like my 6X47L and 3/16" for hunting rifles. Very broad strokes but,

The Problem Exists Folks!!!

I used to shoot with Del Bishop (RIP Dear Man) and he had some awesome cool workarounds... He used foam pads. He adjusted his clothing. He experimented endlessly with how/where/when and how hard to use the forend stop......He used pointy rubber "fingers" and whittled out little soft rubber "touch-points" and was looking for something "stiff enough to stand out like a stiff, ummmm, 'thing', but soft like a gummy bear or a rubber sticky hand" (Del didn't say 'thing')

He also taught me about "kid, that gun wants to shoot, LET IT SHOOT!!!!"

But I digress

My figure of "one tenth of an inch for BR rifles" comes from several sources and is subject to several obvious variables.

And some not so obvious.

Sources;
-Robert Rinker in 'Understanding Firearm Ballistics' uses the figure of "about 60 thousandths for a typical hunting rifle".... imprecise but in general agreement with Toby.

-Robt McCoy details how to figure it and,

-I got a figure of "1/10th of an inch is safe" from Harold Vaughn, because I ASKED HIM..... (As Toby points out, it's all subject to some eddicated guesswork)

AND..... experience lately with 30" barreled 338's in light (7-9lb) rifles is leading me to believe that 1/10th inch isn't always enough...

It's an amalgamation of things..... just like a quarter-mile racecar, every car will get thru the quarter but some faster than others. Some obvious differences are cartridge energy, rifle weight and barrel length. The first time I saw a guy fire a 50BMG pistol I was concerned he'd stuff the thing into his eyesocket cuz I'd fired me some 20 pounders and I KNEW how hard and long they recoiled! But the short-barreled pistol didn't have time to produce much backward acceleration so it was safe to shoot. Plus, since the 50BMG pistol was braked and had tons of leftover gas to work with, it actually flipped up less and came back less than a 500 S&W.

BUT.....

This isn't why I'm posting

I'm asking for help here.... I'm a guy who TESTS stuff and this is one y'all can TEST with me.

When you go shooting take along a hunk of wood dunnage, like a cut off beam end or a hunk of firewood. At the end of the day set up the rifle in the bags and set your dunnage behind the butt angled 45 degrees. Use some rubber sheeting or a piece of leather or whatever but set it up so the gun will hit a glancing blow as it recoils. Using a caliper gage up some pieces of lathe of various thicknesses to set your recoil spacing and fire a few at your groups. Find out for yourself how much room you've got with YOUR setup before it starts spitting shots.

 

[alinwa]

Al,
I do not disagree with your support of Mike, and Im not backing Bart. Thats not how I took your post. But if you think Im just out to be friendly and have not proven any of my ideas I have to strongly disagree with you on that. Advancing the sport does not happen on the internet as you know. If you have good ideas and they work, someone with take them up and put them into production, you dont have to be friendly you just have to prove them. Usually that requires being unfriendly, at least at first. And by the way, I would like it if you could make it to a match out this way. Im always up for heated discussion and its better in person.

OK...... I'm gonna' severiously disagree with something right now

You say "Advancing the sport does not happen on the internet as you know." and this I must disagree with, because what I "know" is that the internet has done more to advance accuracy in a shorter time than any other force in history...

I've BEEN here..... to paraphrase an American Hero, "Hell, I Was HERE!"

I KNOW where this website came from, whence it was spawned and why, because I was part of it.

I KNOW that pre-internet I spent beaucoup dinero on books and 'wayyy more beaoucoup'er dinero ACTING on those books.... and I've watched the information steamroller gather speed for these last 20yrs until we can't MAKE stuff fast enough to respond.....

And I KNOW you know this, because you're one of those DOING IT

(I don't think we disagree here afterall)


LOL



al

 

[mauser284]

Ok, I'm gonna wade in here just a little bit.
You hit the nail on the head when you said that amplitude reduces with mass OVER TIME. The barrel is already deflecting downward before a shot is even fired, due to gravity, though. So, it's first movement is downward as the bullet begins it's travel down the bore. Because the barrel is pre loaded by gravity, it will come up and ultimately, the travel be larger..due to the energy held with the material. Replace travel with amplitude. INITIAL amplitude is increased, but you are right, over time it is less. We are not talking about natural frequencies of a cantilevered beam here, either and we certainly are not talking about much time.

But, at a given frequency, more muzzle deflection, initially, is equal to more initial amplitude. Forget what happens over time as we are dealing with not only natural frequencies but the forced deformation that happens while the barrel is under pressure and slightly after.

To the point...more muzzle deflection equals more amplitude and a larger arch or barrel oscillation. This is clear on target by the large out of tune groups vs. a stiffer barrel and this alone is evidence that the amplitude during the small amount of time involved is increased, not decreased. The larger radius or arch, for lack of a better word, is how mass widens the tune window. This is why a somewhat heavier tuner is best, IMHO. It both increases INITIAL amplitude and decreases frequency. In a nutshell. It slows the barrel down and makes it move in a larger "radius" at the node.

I found this interesting when doing the vibration analysis testing for my tuners because it is counter to common physics studies that mostly address amplitude "over time." But bottom line...initial muzzle deflection is increased by having a mass at the end of the barrel when fired. We measured the amount and times to the point that this was visible when testing different media in my tuner than the tungsten powder matrix that I use for dampening. Regardless of the point you are making, during the time that matters, amplitude is increased by having more muzzle deflection. The only caveat I'll add is that we were testing the affects of adding a mass to the end of the barrel. I don't see much difference though, as adding mass simply makes the barrel act less stiff.

I'm not gonna debate this because I physically measured it and one of my New Year's resolutions is to stay out of pissing matches on here. We'll have to see how that one goes..."over time."

I do like to read your posts and you are a smart man. This is very much a less than obvious result to expect if going strictly by what most research involving vibration will tell you. The key is time. There just isn't enough time before bullet exit occurs to see a net reduction in amplitude. I'm sure the numbers can vary a bit with different barrel stiffness's and the forced deformation that occurs both with and without weight added at the muzzle though. --Mike

So Mike please correct me if I misunderstand you as I want to learn from the knowledge you just dropped for free! If the two resulting barrels had the same final mass and length would it be correct to say that your research indicated it is better to have a Rem' Sendero profile barrel with a heavy tuner on the end than to say have a 1.40 inch straight cylinder barrel all things otherwise being equal? Thanks for your time Mike!

 

[Nick Caprinolo]

I admit I have not read the entire thread and this may have been said before.

It is my experience that the heavier barrels will not heat up as fast as those that taper below .925 at the muzzle. This heat build up will cause bullets to move the aim point, the hotter it gets. Take for instance a hunting barrel. It is designed to place the first cold shot at the point of aim. The second shot will usually be touching it but the third shot will fly away. Fire the first two shots and wait ten minutes before firing the third, and it will go back very close to the point of aim.

If you are worried about weight, then expecting small groups at any range is not gonna happen.

Heat is a barrels worse enemy. It's the major cause of shot out breaches in barrels.

Common sense will tell you that when metal heats up, it changes demolitions. The thicker the barrel, the less it will flex.

This is just my opinion, proven to me through countless treks to the shooting range, with every concealable rifle configuration. I have no science to prove my theory.

 

[Richard Coody]

A whole lot of variables here to think about.

Sure a heavy barrel handles long strings of fire better than sportster profiles. But.what is the intended use. What is too heavy to be practical.

Rifle balance is also a consideration. Sure you can add weight to the buttstock to compensate but when is it too heavy to be practical

I would say anything from a light varmint to a full bull from a top of the line barrel maker you would find more accuracy difference going through 10 barrels of the same contour then you would between all the different contours. Sometimes you just get a hummer and some neevef make the grade

 

[fantastic]

How many times in a hunting situation are you going to get off more than 3 shots. I know it can and does happen, but if I can put 3 shots where I want them and don't have game down, the animal is either out of my range ability wise, or not presenting a type of shot I should be taking. I would worry much more about the accuracy of the cold bore first shot on a hunting rifle compared to where shots 4 and 5 are going. But that's just me. Good luck on your quest.