What difference does a muzzle break have on accuracy?

[bikemutt]

I used to "permanently" mount my brakes, that is with Rockset and a good wrench. I had one rifle, an AR15 upper in 7.62x39, that started to lose accuracy. I decided to pull the brake and discovered it had allowed an asymmetrical buildup of carbon on the muzzle crown. After cleaning the crown and reinstalling the brake (with a jam nut) the rifle returned to it's customary level of accuracy.

Along the same lines, I recently picked up a used JP Supermatch upper in 5.56, it was outfitted with a Bennie Cooley JP brake. I decided to check the upper out a bit before shooting it, the muzzle crown was fouled with the same bizarre asymmetrical pattern noted above. I cleaned it up and reinstalled the brake with a jam nut. I have no accuracy reference with this one, I only mention it so as not to tar 7.62x39 as being remarkably"dirty".

In any event, to answer the OP's question, I would have to say a brake may alter the accuracy of a gun if it alters the muzzle crown in a meaningful way. I no longer use Rockset or any other thread locker on my brakes as I don't feel confident about muzzle crown carbon buildup. Pretty much I use some sort of jam nut which enables easy inspection and cleaning if needed.

 

[zb338]

I have two sons that have Weatherby hunting rifles. One is a .300 W' and the
other is a .340 W'. The muzzle breaks were bought already built and they were
installed by a professional gunsmith. Both rifles shoot very well and the breaks
really cut back on the perceived recoil.

Zeke

 

[benEzra]

A *symmetrical* brake should not hurt accuracy. Some asymmetrical brakes can reduce accuracy, though, such as the slant brake/comp on the AKM and many civilian lookalikes, if they impose non-axial net loads on the bullet. The AK slant brake in particular makes the bullet fly through an asymmetric supersonic gas flow for the first half-inch after muzzle exit, and IIRC can significantly increase group size due to the resulting nutation of the bullet.

 

[SwampWolf]

I have a Savage Model 116 SE, chambered in .338 Magnum that came equipped with a muzzle brake that can be turned on or off. I've seen absolutely no difference in terms of accuracy (or points of impact vs points of aim, for that matter) between the two settings. Can't say the same for muzzle blast in a bad sense or felt recoil in a good sense with the ports open.

 

[MachIVshooter]

MCMXI seems to have proven the reality, all the other posts are just a waste of time.

Well, I can see one post that was a waste of time

His experience is what we call anecdotal. When you combine it with that of myriad other shooters, you start to see a composite that is representative of the whole.

I have had brakes cause no discernible change in POI or accuracy. I've had brakes affect POI but not accuracy. And I've had brakes that noticeably increased group size.

 

[MCMXI]

His experience is what we call anecdotal.

True ... but my experience is with the same brake as the OP shooting the same cartridge. I never stated that my results are applicable to anything but my Dead Air brake on my rifle.

 

[macgrumpy]

Wow, a brake that causes no discernible change in point of impact? So every bullet impacts in the exact same place? That's pretty impressive, I sure wish you'd have taken pictures of that cuz you would be the very first shooter to have ever had that happen.

And you might call a picture of the groups anecdotal but you'd be wrong, anecdotal means something that isn't necessarily true or reliable and a picture of actual groups are absolutely true and a perfectly reliable image of what happened. A picture of an actual event is actually called empirical evidence- empirical means something that is a verified observation, I'd say a picture pretty much fits the bill.

I guess your comment is just another one of those wasted posts, thanks for proving my point. If I add a cute little face will that make my post kinder and gentler...

 

[270WSMANIC]

Who likes muzzle brakes?

My only experience with muzzle brakes was shooting a friends Savage 110 in 300 Win Mag. I shot several shots with his reloads I think 180 grainers. Recoil a bit more than maybe 243 Win. I was shooting off bags over the hood of his truck and yes was wearing ear plugs.
These muzzle brakes are wonderful thunk I, when hunting though you don't wear hearing protection though so I'll try a shot with no plugs in.
One of the biggest mistakes I ever made. Ear rang for a hour or so. Maybe wouldn't have bin quite so bad if not for the hood and windshield bouncing the sound back at me but that done it for me and the muzzle brakes.
My question are they all that bad or has somebody found a way to make them quieter, and if so how much quieter?
Edit- I meant to start a new thread with this post, some how it got put here???

 

[MachIVshooter]

True ... but my experience is with the same brake as the OP shooting the same cartridge. I never stated that my results are applicable to anything but my Dead Air brake on my rifle.

Your contribution in this thread is a very valid one. Mcgrumpy simply needed to have it pointed out to him that it's not the only valid one He stated, in a profoundly rude way, that your results are all that matter.

 

[murf]

macg,

photoshop ... you are wrong again.

lighten up and quit taking the low road. no personal attacks here.

murf

 

[macgrumpy]

murf -Photoshop? You're kidding right?

And gee, excuse me for pointing out when somebody uses words improperly. I'm not the angry person here, in fact, I'm chuckling at what a manipulative schemer you are - twisting the truth and trying to create an argument where there is none. All I did was point out how a word was used improperly and that makes me some kind of bad person? How pitifully silly.

 

[MachIVshooter]

And gee, excuse me for pointing out when somebody uses words improperly.

You may want to retract that statement.


Definition of anecdotal

1
a : of, relating to, or consisting of anecdotes <an anecdotal biography> b : anecdotic 2 <my anecdotal uncle>

2
: based on or consisting of reports or observations of usually unscientific observers <anecdotal evidence>

3
: of, relating to, or being the depiction of a scene suggesting a story <anecdotal details>


Your definition:

anecdotal means something that isn't necessarily true or reliable

Does apply to several words in our lexicon. But anecdote ain't one of 'em.

 

[denton]

In order to understand how brakes and the BOSS affect accuracy, it is necessary to understand barrel whip. Several posts have been close to the mark, but I think not quite on.

Sound travels about 10X as fast in steel as it does in air. The vibration of the firing pin drop, the ignition of the primer, and the ignition of the powder cause the barrel to vibrate. The vibrations get to the muzzle before the bullet does.

The tip of the barrel moves, probably in an ellipse or a straight line. Near the ends of these figures, the barrel moves much more slowly than it does in the center. Think about a swing, where the rider pauses for an instant at the front and back of the arc, but travels very fast at the center.

There are two effects at work, and I don't know if anyone has separately measured them. One effect is that the barrel is pointing in different directions at different times. The other is that the motion of the barrel imparts a sideways motion to the bullet. Both of these effects are minimum near the ends of the line or the ellipse. If the bullet exits the muzzle near the end, POI variation caused by muzzle velocity variation will be minimum.

The BOSS tunes the resonant frequency of the barrel so that the bullet exits near the optimum point.

Adding a weight at the end of the barrel--sometimes as much as 2 lb--supplies inertia that makes it harder to move the tip of the barrel, limiting the amplitude of the vibration.

So, typically, adding a mass such as a brake will possibly change both POI and group size because it re-tunes the barrel. However, it also presents an opportunity to tune the barrel to where you want it, by slightly adjusting the position of the brake, as the BOSS does.

 

[Reloadron]

To illustrate what Denton is saying in a cartoon format:

The "whip" theory suggests a barrel's thickness and length impacts how much it moves with each shot. Indeed, a short thick barrel mounted nearly in-line with the stock butt (as used on bench rest rifles) should produce far less "whip" then a field profile long hunting barrel with a high cheek piece.

A good write up and explanation in addition to Denton's fine explanation can be found here for the curious at heart. Wouldn't it be nice if we could tune the barrel so our bullets would always exit at the nodes? If I can tune a muzzle brake and shift the nodes I would have to think or believe that a muzzle brake when adjusted, can impact accuracy with accuracy defined as unbiased precision.

A good Google will bring up a wealth of information on "barrel whip".

Ron

 

[Bart B.]

Check out the link in post 24 then you may be able to understand how barrels whip before the bullet exits.

Another good bunch of info is in:

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

and

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

The best place for a given bullet leaving at a given velocity is the angle that compensates 100% for its velocity and drop at target range. It may not be in the center of the whip cycle as shown in the graphics above. Closer too the top on the upswing is often better. Besides the rate of angular change at mid point is the highest and that may cause excessive vertical swinging compared to leaving near the top where the rate's less.

Browning claims their BOSS system puts the bullet out at oone of those nodes when the barrel's straight, but they don't say if its on the up swing or down swing. If it's on the down swing, that's counter productive. I've asked them a couple of times and they have never responded to my queries.

 

[MCMXI]

So, typically, adding a mass such as a brake will possibly change both POI and group size because it re-tunes the barrel.*

But the likelihood of a brake changing the point of impact is a function of the mass and length of the barrel, the mass and design of the brake and even the type of ammunition being used. A 4oz brake on the end of a #0 sporter barrel will have a much greater affect on harmonics than the same brake on the end of an MTU #10 barrel. That being said, I would never have expected such a small POI shift (group center) for my POF P308 when comparing suppressed to unsuppressed, particularly when you consider that the suppressor weighs 20oz and is almost 8" long. The group center only moves about 0.5" left and the same up. My AI in. 308 Win with a 13oz titanium suppressor has about a 3" shift down (no windage shift) with the suppressor attached. The POF barrel is 20" compared to the 26" medium Palma on the AI.

 

[MCMXI]

Wouldn't it be nice if we could tune the barrel so our bullets would always exit at the nodes?

That's what we try to do when we work up a load for a rifle.

The tip of the barrel moves, probably in an ellipse or a straight line.*

I believe that the muzzle moves in a spiral pattern (possibly an elliptical spriral) up to some maximum diameter or axis then back to the center and repeats at some frequency.

 

[denton]

I believe that the muzzle moves in a spiral pattern (possibly an elliptical spriral) up to some maximum diameter or axis then back to the center and repeats at some frequency.

Could be an ellipse, straight line, figure 8. Since the gun is moving backward, in 3 dimensions it could be a spiral. Sure. Good point.

If it's on the down swing, that's counter productive. I've asked them a couple of times and they have never responded to my queries.

That's because it is not the objective of the BOSS system to compensate for bullet drop.

The best reference I have on the subject is Harold Vaughn's Rifle Accuracy Facts. He did some Finite Element Modeling that suggests that the quest for barrel stiffness is counterproductive. What counts is the amplitude of the barrel vibrations, so it's mass that is important. His conclusion was that if you could build a barrel out of something more squishy, like lead, you'd get better accuracy. This would indicate that fluting a barrel may not be helpful, since it reduces mass while keeping stiffness. Browning puts vibration damping material in the barrel channel of the stock, and that seems to help.

 

[Bart B.]

The only way Browning's BOSS (with or without the brake) can possibly work is changing the frequency the barrel whips at to compensate for greater drop slower bullets have by launching them at a higher angle. People have been doing that for decades; moreso with 22 rimfire rifles than centerfire ones.

Fluting a barrel may not be helpful, since it reduces mass and stiffness. It removed strips of metal from the barrel's outer limits that has weight and resisted the barrel bending. After fluting, there's less metal to resist bending and it's lighter. It'll whip at a lower frequency than it did before. Fluted barrels are always less stiff.

Browning puts vibration damping material in the barrel channel of the stock, and that seems to help? Please explain how it works.

 

[CANNONMAN]

Yeah, OK, But... Harmonics aside, wasn't the brake designed for recoil? Wouldn't type and # of riflings affect harmonics? Wasn't the role of flueting supposed to alleviate harmonics? Why not design a barrel to counter whip if not the bull or fluetted? If the goal is for the bullet to leave at an upswing node then why not a shock absorber prior to the break? Free beer and BBQ to all who want to come over for a possible endless number of what-ifs.

 

[denton]

The only way Browning's BOSS (with or without the brake) can possibly work is changing the frequency the barrel whips at to compensate for greater drop slower bullets have by launching them at a higher angle.

Bart, no disrespect, but that just isn't the case.

Even closely matched cartridges will vary in bullet transit time down the barrel.

If the resonant frequency of the barrel is such that bullets are exiting near the center of the muzzle's arc, then a small change in transit time will result in a relatively larger shifts in POI from bullet to bullet. Groups will be larger.

If the resonant frequency of the barrel is such that bullets are exiting near the ends of the arc, then a small change in transit time will result in relatively smaller shifts in POI from bullet to bullet. Groups will be smaller.

Near the center of the arc, the barrel is moving faster. Near the ends it is moving slower, and even stops for an instant.

Browning puts vibration damping material in the barrel channel of the stock, and that seems to help? Please explain how it works.

The damping material reduces the amplitude of the barrel oscillation/whip by absorbing energy.

Harmonics aside, wasn't the brake designed for recoil?

Yup.

Wouldn't type and # of riflings affect harmonics?

Not so you'd notice.

Wasn't the role of flueting supposed to alleviate harmonics?

Nope. It's supposed to reduce weight while retaining practically full barrel stiffness. It's also highly decorative. As I said earlier, many people mistakenly think that it's barrel stiffness that counts, when it is actually barrel mass.

If the goal is for the bullet to leave at an upswing node then why not a shock absorber prior to the break?

That's not the goal. But shock absorption is exactly what Browning does, to reduce the amplitude of the barrel vibration.

 

[Bart B.]

OK, if BOSS times the barrel whip so bullets exit at one extreme of its whip, which one is it?

Top? Or bottom?

How many whip cycles does the barrel at its muzzle axis does it go through before the bullet exits?

I'll assume that because all bullets of the same load don't have the same barrel time because of muzzle velocity spread yet the barrel's resonant and harmonic frequencies are constant for each BOSS setting, they'll bracket their exit points about one extreme or the other. OK?

 

[denton]

OK, if BOSS times the barrel whip so bullets exit at one extreme of its whip, which one is it?

Top? Or bottom?

Barrel whip can be up and down or side to side or diagonal. It does not matter whether bullets exit at the top or the bottom, the left or the right. What matters is that they exit near one of the extremes. That produces the smallest groups. Then you adjust your optics so that POI aligns properly with POA.

How many whip cycles does the barrel at its muzzle axis does it go through before the bullet exits?

I don't know. Fortunately, it's not important.

I'll assume that because all bullets of the same load don't have the same barrel time because of muzzle velocity spread yet the barrel's resonant and harmonic frequencies are constant for each BOSS setting, they'll bracket their exit points about one extreme or the other. OK?

I'm not sure I'm understanding you correctly. But the right idea is that bullets that exit near the ends of the arc will be more tightly grouped than bullets that exit near the center.

 

[Bart B.]

Yes, bullets leaving near the top and bottom of barrel whip arc will depart in a smaller angular spread. But if it's at the wrong place, it'll distribute bullets in a greater vertical spread on target than at the right place.

Did you check out these links I mentioned earlier?

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

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

It an others on that page, they clearly show that most of the barrel whip axis is in the vertical plane. Therefore, bullets leaving at the extremes of vertical whip cycles will depart at certain angles relative to the line of sight as follows:

If bullets leave about the upper limit, those with faster velocities will leave on the last part of the up swing and slower ones on the first part of the down swing. Fastest ones are positively compensated for their departure angle as they leave at a lesser angle on the muzzle upswing than those not quite as fast closest to the cycle apex. Slower ones will leave later after the muzzle axis is at its peak on its down swing. The slowest ones leave later at a lesser angle to the LOS than those not quite as slow leaving at a higher angle; they are negatively compensated for because the slower ones need to leave at a higher angle to compensate for their greater drop at target range.

If the bullets leave about the bottom of the barrel whip cycle, the effect is opposite of the above.

Should all the bullets leave just after the muzzle axis is at its top most point and on the down swing, all bullets are improperly compensated for because the faster ones leave at a higher angle to the LOS than the slower ones. This increases the vertical shot stringing at target range.

If all bullets leave on the upswing, they are all positively compensated for their velocity. Fastest ones leave at a lesser angle sooner than slower ones leaving at a greater angle. This is positive compensation for all bullets. This reduces vertical shot stringing at target range. Mid range stringing will be greater but that's not where the target is. Positive compensation is at its best at only one range. So a happy medium is often a good compromise.

Varmint Al referenced this article:

http://www.ozfclass.com/articles/1/psm_2005_03.html

... which is often thought correct but's been proved wrong many times. You can see the realities of barrel whip angle versus bullet exit points using the following:

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm

It all boils down to the fact that only when bullets leave on the muzzle axis up swing are all fired shots compensated for their drop at target range; slower ones at a higher angle, faster ones at a lower angle. Any bullet departure on the down swing is contrary to the objective of having all bullets land close together in the vertical axis.

 

[MCMXI]

It an others on that page, they clearly show that most of the barrel whip axis is in the vertical plane.

It makes sense that the long axis of an elliptical spiral (muzzle movement) would be in the Y direction due to gravity acting on the barrel and the fact that a free floating barrel is a cantilever beam. But the barrel is free to move in any direction that isn't constrained. It's simplistic to assume that muzzle movement in the X direction can be discounted.