The other day I swapped scopes on my browning xbolt. Sighting in, the first rounds were with a muzzle brake, the last few were without. All rounds were chronographed, and it was a beautiful sunny day. Rounds with the muzzle break were 69 fps faster on average than without. Odd?

Hmmm....🤔

Sounds to me like the outcome of random chance when dealing with a statistically insignificant sample size.

That or something is up with my chronograph. 3180 fps with a 160 Accubond is trotting along a little hot in a 7mm rem mag.

This...

What chronograph ?

I’ve seen that several times over the years with my braked rifles. Some rifles do it, some don’t.

Something could be broken besides the muzzle.

Very well done!

^

Brake: a device for arresting or preventing the motion of a mechanism (like the reward travel of the rifle)

Break: to separate into parts with suddenness or violence. (like the gas leaving the muzzle)


They both work.

They both are derived from the same word.

Just based in the thread title alone.

Adorable, I used the wrong term of break instead of brake. Yall so punny.

It's a Shooting Crony "gamma master".

Defiantly something broken besides the muzzle then. #chronographsmatter

Poking the bear aside, Shooting Chrony doesn't have a great reputation for consistency. Were lighting conditions different between shots?

Muzzle blast --- just saying !!

Thanks for the info. I don't know much about different chronographs, this unit is one my buddy bought and left at my house.

Lighting conditions were generally the same, full early afternoon sun. I had the poles and sunscreens setup. I set the chronograph about 11 feet away and have the angle set so that my horizontal reticle crosses all four brass connectors on the sunscreen poles and the vertice is through the center and on the target.

Maybe the unit is junk.

Try setting it 20 feet from your rifle. Muzzle blast from the brake can interfere with bullet velocity measurements.

[ this unit is one my buddy bought and left at my house.] - I like those kind of buddies!

[Maybe the unit is junk] - It might or might not be "junk", but if it repeatedly and consistently shows you get higher velocity with the brake installed than without, it is still telling you an interesting fact. I suggest you repeat this effort any time you go to the range and find out.

Have you ever pulled a travel trailer with someone following closely? When the air is disturbed the vacuum is broken, velocity will increase.

Wouldn't the muzzle blast from the brake be headed away from the crono.....?

You'll often see similar changes in velocity with two different people shooting the same rifle/load. You can also see significant changes in velocity shooting the same rifle/load prone, benched or standing. The more the rifle moves rearward as the bullet moves down the barrel the slower the muzzle velocity will be. Brakes reduce the velocity of the rifle rearward so will often increase the bullet velocity at the muzzle. If you were to prevent the rifle from moving rearward by placing the butt against a rigid object, you would in theory see the maximum velocity possible because more energy is available to push the bullet down the barrel rather than being used to push the rifle rearward.

I would agree it was being "Defiant" 😁 My truck has "breaks" and when I apply them it never speeds up 😂

Don't all the effects of using a brake happen after the bullet has left the muzzle and the brake alters the flow of the gasses escaping behind the bullet?

Okay.............ummmm

Trystan - Hanco - Pete 53 = Trystan - Hanco - Pete 53

Yea campfire.


Jerry

Yes, but if the expanding gasses in the barrel only push the rifle rearward when the bullet is in the barrel, would brakes have any effect at all?

I’m not so sure about all this. Muzzle velocity is not relative to the position of the bore. It’s relative to the fixed position of the measuring device.

"... you would in theory see the maximum velocity possible because more energy is available to push the bullet down the barrel rather than being used to push the rifle rearward."

For every action there is an equal and opposite reaction. Doesn't matter where your butt is.

This is your main problem.

The muzzle brake diverted a lot of the blast, but the bare muzzle probably allowed gas to reach the chrono. Muzzle blast definitely messes with the readings on optical chronographs, and the Shooting Chrony brand seems to be more sensitive to stuff like that.

My suggestions - step back to ~20 yards (not feet) to eliminate muzzle blast issues and try again. I get more consistent results standing at least 10-15 yards away with magnum rifles, and a little farther is better.

Also, buy a better chrono when you get a chance. For about the same price the Pro Chrono DLX is pretty good, or you can spend a lot more of course.

Yes. After the bullet leaves the barrel, the gasses push forward on the brake; that force counters some of the rifle's rearward movement.

Think of it like this:
You have your car in reverse, and want to back up at a certain speed. You stab the throttle and it jumps backward too much, so you then apply the brake to slow it down a little. The brakes in your car are doing the same thing as a muzzle brake. (and the word brake means the same concept in both cases.)

Yes. Sorry for the confusion, my point was that the difference in muzzle blast directed toward the chrono between braked and un-braked can mess with the readings of two bullets of identical velocity.

Yes, thank you. I don't know what I was thinking when I posted 20 feet. I typically have the chrono set at 15-30 meters to completely eliminate any problems related to muzzle blast. That should have read 20 yards, not 20 feet, though 20 feet is a lot better than 11 feet

This is very true, and the bullet's velocity should be the same either way. The rifle is set in motion and gains momentum while the bullet is in the bore, and when the bullet leaves the bore, the rifle has a certain amount of rearward velocity. This is regardless of whether or not there is a brake on the muzzle. This answers MCMXI's point about conservation of momentum affecting the bullet's velocity. Then after the bullet exits the muzzle, the blast radiates outward from the muzzle and hits the ports of the brake, pushing the rifle forward, as Yondering described, but that takes place after the bullet has exited the muzzle and has stopped being accelerated by the pressurized gas in the bore.