Browning rifles with BOSS system

Is that maximum muzzle deflection when the muzzle axis angle is at either extreme from when it's straight out in a static condition and at either extreme of angular displacement due to the barrel bending from shock from firing?

Has Browning always bedded BOSS equipped rifles in hard rubber urethane?
 
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Yes ... the shock from firing initiates the vibration ... the frequency of the vibration is going to be the resonant frequency of the barrel system. To the best of my knowledge, Browning has always used Flexane 80 (or 85) ... at least that is what they disclosed in their patents. The Flexane will actually attenuate the vibration a little. It's kinda messy stuff to use, but it does work.

Saands
 
A 30 caliber 30 inch long 5.1 pound Palma barrel or a 26 inch 4.4 pound heavy sporter barrel is not as stiff as a 22 inch long 2.1 pound featherweight 30 caliber barrel. That Palma and heavy sporter barrels resonant frequency is about 39 Hz while the featherweight one's 64 Hz. They go through one 360 degree whip cycle in 1/39th or 1/64th second.

Typical barrel time for most bullets is 1/800th to 1/900th second. Bullets leave the barrel long before the muzzle axis moves 90 degree down which is its first direction with conventional stocks.

How is it possible for a bullet to leave at an extreme muzzle angle at those resonant frequencies in the range in what most barrels have?
 
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A 30 caliber 30 inch long 5.1 pound Palma barrel or a 26 inch 4.4 pound heavy sporter barrel is not as stiff as a 22 inch long 2.1 pound featherweight 30 caliber barrel.
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I'm not sure where you got your stiffness and resonant frequency values, but it seems very counter-intuitive that the skinny barrel is stiffer than the heavy barrel. Also, the values of the resonant frequencies seem awfully low. When you whack a barrel (of any shape) with a hammer, the sound it makes is not that of deepthroated tenor, it sounds like a high pitched "piiinnnnnng" ... It's getting to be bedtime here, but tomorrow I will grab my Roark's Handbook and run the numbers on a barrel. One last thought is that maybe it is the higher-order harmonic that we are hearing and if so, then it would be those that would be affecting the accuracy. I'll let you know what I find.

I will say that if your numbers are correct, then you are making a VERY good point.

Saands
 
Just did a quick calc on a 1" thick piece of steel that is 20" long (those numbers were easy to run) and its resonant frequency is 16kHz ... the first harmonic is just a tad more than 100kHZ ... Since the resonant frequency varies with the square root of stiffness/mass ... the tube's numbers should be even higher.

More to follow ...

Saands
 
In your calculations, be sure the bore diameter, the barrel's profile and section taper lengths and diameters are correct. Use fixed breech end formulas as barrels alone in space have different resonant frequencies than those screwed into receivers solidly affixed to the stock.

The high frequency made by sound waves bouncing back and forth (traveling about 16,000 fps in type 316 stainless steel) are not what barrels whip like fishing rods do when casting lures. Rods and barrels fixed at one end whip at very low frequencies typically under 100 Hz. Example below:

http://www.varmintal.com/amode.htm

There's other examples on his web site.

I'll use the software I asked Tom Irvine's company to make (rifle frequency) below:

http://www.vibrationdata.com/updates.htm.

to calculate a 24" long barrel weight and resonant frequency for a barrel dimensioned as follows:

1.2" dia. x 2" long reinforce (1" long tenon in receiver not used)
1.2" dia. x 2" long x .9" dia. taper
.9" dia. x 19" long x .6 " dia. main taper
.306" bore dia. (.0736 square inch area typical for 30 caliber)
316 stainless steel
Breech fixed

Chamber volume not used. If used, resonant frequency will be a little less. We can compare results. They should be very close, if not the same. Note that the mass of the stock and scope attached to the barrels breech end will alter frequency calculations because they're part of the whole rifle that wiggles when fired. It's best to assume a solid mounted receiver to see what the barrel alone vibrates at when fixed at its breech.

First study on a barrels low frequency vibrations in the vertical plane was made over a century ago. Enjoy the math but the last page is the overall conclusions:

https://archive.org/details/philtrans05900167

99% of all the rifle barrel vibration stuff on the internet is bogus babbling developed to satisfy an incorrect assumption. It's well understood that slower bullets have to be launched at a higher angle than faster ones to strike the same place on target. The only part of the vertical muzzle axis swing that does that is the upswing. It's impossible if bullets leave at the extremes where the axis reverses as half would leave on the upswing and half on the downswing due to normal spreads in barrel time and muzzle velocities.

Fluted barrel stiffness blasphemy is common, too.
 
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Then there was the Model 70 with the bulge in the barrel. About 8 years ago there was the 'dog knot', it was the rage, just slide it back and forth to obtain the sweet spot?

Then there is the ugliest rifle ever "sporterised". I did not think anyone could build something that ugly without knowing more than his critics...about guns. I bid and won the auctions, $120.00. I went to the range with 12 different loads 10 rounds each. After firing all the ammo over a period of a day I applied the leaver policy, I decided to leaver the way I purchased-er. the rifle was purchased for parts, not easy to build a rifle with a better predictive accuracy.

F. Guffey
 
As long as bullets leave anywhere on the muzzle axis upswing, the velocity spreads they have will be fairly well compensated for.
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You say Browning "hasn't proven" the bullets leave at an upward swing of barrel movement

You say it HAS been proven the best accuracy is when the bullets leave on an upward swing

It HAS been proven the "BOSS" improves accuracy, so that in itself proves the bullets must be leaving on an upward swing

All the talk about what can be done with powder charges is meaningless, since the majority of shooters do NOT reload.

The whole premise of the BOSS is you can choose the load first, and adjust the gun, and not vice versa
 
99% of all the rifle barrel vibration stuff on the internet is bogus babbling developed to satisfy an incorrect assumption
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The same could be said about most posts on internet forums.
The longer the posts, the more likely it's babbling ;)
 
It HAS been proven the "BOSS" improves accuracy, so that in itself proves the bullets must be leaving on an upward swing.
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I disagree. Accuracy can also be improved when bullets leave on the muzzle axis down swing. That's done by shifting their exit point from the middle portion of the swing arc where the axis angle rate of change is the greatest to near the extreme where rate of change is the smallest.

My point is based on Browning's claim that a perfectly adjusted BOSS lets bullets exit when the muzzle axis is straight out with the original bore axis before firing. They don't know if its on the axis down swing or up swing. If they do, they chose not to tell me; in fact they never answered my queries about it at all. It will help if it's on the up swing, but make it worse if on the down swing. I don't think they understand how the trajectory path changes for bullets leaving slower or faster than average on the axis down swing that worsens down range accuracy.
 
My point is based on Browning's claim that a perfectly adjusted BOSS lets bullets exit when the muzzle axis is straight out with the original bore axis before firing.
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That's not what you said before, and I've never seen Browning make any such claims:

Browning claims their BOSS adjusts the barrel whip frequency so the bullet leaves when the barrel's stationary.
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I disagree. Accuracy can also be improved when bullets leave on the muzzle axis down swing.
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If you "disagree" then you're disagreeing with yourself, because again you've changed what you said:

'Twas proved over a hundred years ago that the best place for bullets to exit is just before the muzzle angle reaches its highest value as it swings up.
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It will help if it's on the up swing, but make it worse if on the down swing
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Now you're just flip flopping all over the place ;)
 
It's ugly as sin!

I thought when I purchased my model 70 Winchester with a boss it wouldn't matter, well it does matter, I hated mine.. The boss changed the look and profile of what I consider a classic hunting rifle that Jack O'Connor had been writing about for years. To me it didn't matter if the boss were on or off it ruined the profile of a classic rifle plus it changed the way it felt and balanced. I couldn't get rid of the rifle fast enough. Thumbs down, this was difficult to write because everyone wanted the riflemans rifle when I was a young man. Now I can afford to buy what I want, I still want the classic look of the model 70 Winchester in the rifle I buy. I'm giving some thought about another Winchester model 70 in 30/06 maybe for Christmas, if I do it will be number four!! William
 
There has been talk of "upswing" and "downswing" in regard to the vibrations of a barrel. Being ignorant on the specifics of barrel vibration, can someone tell me if the vibrations are always oriented vertically? Are some horizontal (side to side), or even both (a figure eight)? And, how does one know?
 
Most of the barrel vibration amounts are in the vertical plane as the recoil axis is above the center of the butt plate. But there are smaller ones in all axes. Google "varmint al a mode" and click on the tuner analysis link. The barrel harmonic movie link shows vibrations at all the major harmonic frequencies above the low resonant one the barrel has.

Browning states the BOSS tunes their barrels such that bullets leave between vibrations. In my opinion, that's when the barrel is as straight as possible with minimal bending when vibration amplitudes are smallest. The barrel is never still or stationary as Browning claims when the bullet exits. There are several frequencies barrels vibrate at simultaneously. The amplitude of lower frequencies are larger than higher ones.

The best tests proving horizontal vibration were Audette's verifying out of square bolt faces impact on shot stringing. With. Vertical positioned locking lugs, their lack of back thrust of case heads against the sides of the closed bolt allowed greater amplitudes of barrel whip in that axis.
 
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Would like to understand, aside from barrel trim length, if there is any realistic control for timing Bart B's bullet release to up-side climb?

I suppose examination of all the physics of firearm dynamics has long been evaluated, but seeking to control the bullet release seems to be more an Artillery concern and likely one for 10-16" naval or railroad car positioned guns? I understand that benchrest shooters, at least those firing the traditional 100/200yd match, have long proven that 20-22" barrel length is about optimum for accuracy/precision results due to barrel weight & contour reducing muzzle whip and smoothing-out vibrational wave-form.

Bart, are you saying the optimum is bullet release on the climb of the vibrational wave? How is that actually measured with so many influential variables? Almost seems like a philosopher's "how many angels could dance on head of a pin" issue...


As for the BOSS system, I would prefer a more rugged lock nut. Something like two opposing nuts that could be wrenched together for improved stability and assure that the setting remained constant. The lock ring is very flimsy.
 
Yes, there is realistic control of the timing the bullet exits the muzzle. Longer barrels have longer barrel times. Different powders have different pressure curves which determine when the bullet leaves a given length barrel. Changing the barrel's weight, length and profile changes its resonant and harmonic frequencies.

The optimum is bullet release on the climb of the muzzle axis, not just a vibrational wave. The Brits proved that a century ago with manual mathematics in the following link (click on the PDF file link on the left side):

* https://archive.org/details/philtrans05900167

No wonder their SMLE .303's shot more accurate at long range than our M1903's. Even with twice the muzzle velocity spread their cordite-powered bullets had.

...and more recently by computer software:

*http://www.varmintal.net/aeste.htm

* and the following links on the left side of that page:

Esten's Rifle & Tuner
Light Rifle & Tuner
Barrel Harmonic Movie
Barrel Tuner Analysis
6PPC Barrel Dynamics

It's fairly easy to figure out what part of the muzzle axis vertical swing axis is best for the bullets to leave at. The angular rate of change is largest when that axis is straight out; smallest and going through zero at the top and bottom of its arc. Slower bullets leave later that faster ones about the average barrel time from case mouth to out the muzzle. Faster bullets of the same BC drop less at given points down range; slower ones drop more.

16 inch battleship 66' 8" long gun barrels have enough "droop" at their muzzle (point at a lower angle than the breech axis from weight) that it's calculated for in gun elevation orders by the Mark 8 Range Keeper (mechanical ballistic computer) and the elevation angle's increased a bit to compensate for it. Their powder charges are three 110-pound bags for reduced loads or six bags for full power loads with 1800-lb. HE or 2700-lb. AP projectiles. No barrel whip vs bullet exit tests were ever done on them as far as I know.

How many angels could dance on head of a pin? That depends on the size of both the pin head and angles as well as the dynamics of the dance. There's at least three variables involved. And more, probably on a flat head pin than a round one.
 
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Does the BOSS really work?

I just joined this site, and saw a lot of interesting views on the BOSS device used on many Browning rifles. My working knowledge of accurate firearms comes from my 31 years as a LEO and using heavy barreled 308 sniper rifles. I became a firearms instructor about 8 years into my career. I don't profess to be the worlds authority on accurate rifles, be few people have the importance of an accurate shot placed on their shoulders like a police marksman has. If you miss a deer or a paper target....oh well, try again. You miss a hostage taker, or hit the hostage, your life as you know it will change forever. I stated that above to set the stage for any information I may interject into this discussion. What ever I report has been done by me, or by a student with me. So I'm not into stories or BS. Now about the BOSS. First BOSS equipped rifle I owned is a Browning Composite Stalker, in 7MM Rem Mag. This rifle was bought used but not fired. The owner was killed in a fatal MV. So I went through the recommended break in procedure. (shoot one, clean the bore at least 10 times) So the rifle shoots very well. First rounds of 120 Gr. Sierra Spritzer W/ 65.8 Grs of I 4350. I started here and had a 4 in spread on two rounds. Adj the BOSS a tenth turn at a time worked it to two rounds touching at 100yds. The rounds almost the same hole. (center to center about 3/8 in)This was done on a Lead Sled to remove the human error. This group was stable out to 350 Yds. This is the max distance at my shooting club. What it does beyond that is not known for sure.(by me) The 350 yd group was about 3/4 in. I said the group was stable not still on top of each other at 350yds.I would not be afraid to shoot a Prong Horn out to 600 yds or more. I would want to shoot the real distance before attempting that shot, to dope the scope.
I have kept the heat down on the rifle by not shooting more than 2 to 3 rounds at a time. Moving on when back to ambient temp. Next load was Nosler 150 Gr. BT (red tip). 61.0 Grs. H 4350. at 350Yds. was just under 2.0 in. I failed to state the BOSS settings. First load 120 Gr = 1.0 to 1.1. the 150 BT = 3.0. The last round I tested was 168 Berger VLD 71.Grs H-1000 w/Boss set at 7.0. The vld round seamed to be open to 2.0 in at 200 Yds. and closed to under an inch at 350Yds. I have heard that the berger takes more distance to fully stabilize. This could be true, I'm not done working this round yet. To make a long story short, does the BOSS work? I say yes, can this kind of accurate shooting be had with custom loading. I say yes to that also, depending on the accuracy of the barrel. If your rifle isn't perfect, and many are not, the Boss can help that drive to perfection. By the way I went through 8 different sniper rifles (Dept money of course) to find a 308 to fit my need for an accurate stopper of EVIL deeds. I am now retired and I miss my rifle. But I own a BOSS life is good. Just got an 06 with a BOSS, will let you know how that works out.

Remember "The 2nd amendment is in place, in case they forget the others."
 
Hawkeye53, have you ever shot several 2- or 3-shot groups a few minutes apart (to cool the barrel down) to see how many shots would group at 300 yards?
 
Response to Bart.B about BOSS

I found that if I shot several rounds in a short span of time and really heated the barrel the groups would open up. The heavier bullets would string out. I try to do any testing with hunting in mind. The chance of taking more than 2-3 shots in a row, have been remote. My 7mm has a sporter barrel, it heats up quick. So I like to test under conditions of a hunt. I have been very happy with the cold bore performance of the 7mm. I don't hunt with a just cleaned bore. I will fire a couple of fouling rounds then case the rifle. So far that has worked for me.
Just for added info I shoot a Rem 700 308 168Gr. A-Max w/ 44gr of BLC-2 with a stainless fluted barrel and have not had a heat problem at all. This rifle will shoot a dozen rounds in a row and hold a very tight group. I don't hunt with the 308, a bit heavy to walk all day. Great if you have a bench.
 
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