Can switching muzzle brakes change muzzle velocity??

[TXAoudadKlr]

Personally I didn't think the muzzle blast was all that bad with my 338LM and T3. I do remember getting some dirty looks when I touched off round number 2 with my 300AX and a PK brake but I was also setting off 16 more grains of powder at higher pressures vs my 338 which runs a pretty mild load.

 

[Doublezranch]

I know I'm late but hoping to be fashionably late. I have shot Assassin brakes since they came out with their 50 bmg prototype. I think they are so wonderful. I've shot lots of brakes but never one that would let my (12 year old) at the time shoot a 7 RUM comfortably. I just built a 378 Weatherby Improved for my now 15 year old. He never wants to stop shooting. Between my 11 year old daughter shooting a 25 wssm with a assassin, and my son with his 378 imp, the assassin brake really knocks down the recoil and makes life easy for the shooter.

 

[adrexco]

from a point of view of fluid dynamics, a brake must have an effect on the projectile velocity, The supersonic fluid column accompanying the projectile has to extend past the end of the barrel. A portion of the recoil energy is the thrust created from the exiting fluid column. Otherwise a brake would have no effect. Redirecting the laminar fluid column flow to a significantly different vector (like close to 90 deg) must have an effect on the projectile velocity. The more efficient the brake is on redirecting the fluid column thrust (reducing recoil), the less of the fluid column energy is available to assist the projectile against the static friction of atmosphere.
I haven't really thought about this before, but I think there is more going on in the first foot or so of external ballistics then I've considered in the past. A very interesting thread!

 

[IdahoCTD]

Go look at the video link I posted. I tested numerous different brakes with different baffle angles and effectiveness and there is no significant change in velocity. The ES was less than 20fps on a 338 Lapua even without a brake. The pressure drop is so drastic when the bullet leave the barrel because the gases have somewhere else to go besides right behind the bullet, the path of least resistance. The gases have to be contained to effect the bullet and that is why suppressors are faster than a brake or nothing at all. A brake doesn't effect the gases that follow directly behind a bullet, only the gases that deviate from the bullet path. Once the gases deviate from the bullets path they can't alter the speed of the bullet in any way shape or form but they can be used to reduce recoil.

If you've watched slow motion video of a bullet exiting a barrel you'd see how fast the gases dissipate and sure the gases will continue to accelerate a bullet slightly once it leaves the barrel. Like I already said, the gases that effect a bullets velocity can't be touched by a brake.

 

[Timber338]

Go look at the video link I posted. I tested numerous different brakes with different baffle angles and effectiveness and there is no significant change in velocity. The ES was less than 20fps on a 338 Lapua even without a brake. The pressure drop is so drastic when the bullet leave the barrel because the gases have somewhere else to go besides right behind the bullet, the path of least resistance. The gases have to be contained to effect the bullet and that is why suppressors are faster than a brake or nothing at all. A brake doesn't effect the gases that follow directly behind a bullet, only the gases that deviate from the bullet path. Once the gases deviate from the bullets path they can't alter the speed of the bullet in any way shape or form but they can be used to reduce recoil.

If you've watched slow motion video of a bullet exiting a barrel you'd see how fast the gases dissipate and sure the gases will continue to accelerate a bullet slightly once it leaves the barrel. Like I already said, the gases that effect a bullets velocity can't be touched by a brake.

Ya you've done some very cool tests/videos!

In theory I have to agree with what adrexco said, but it's certainly is hard to argue with your real world testing... Especially since you have tested such a similar setup to my 338 RUM shooting 300 grain bergers in the RUM cartridge. It's more or less the same as a Lapua.

In my mind just shows I don't know what the heck is going on! And also still leaves me confused at the real source of my 47 fps velocity drop. I did not test side by side on the same day with the different brakes. But it is a thoroughly tested and consistent rifle. Since all rifles and setups are different, my mind is going to lean towards the brake being the cause (even if I'm wrong) until I figure something out that proves true root cause.

Idaho, you certainly have a lot of experience testing a lot of different brakes and thanks for chiming in here and sharing your videos. They are very helpful. So please don't think I'm arguing with you or saying you're wrong. I think you've got a better grasp on this than most of us my brain just takes a while to catch up and figure things out.

 

[IdahoCTD]

The theory is sound but like I said, the brake can't touch the gases that directly effect the bullets velocity until they deviate from a bullets path. Typically a brake is opened up .020-.030" over bullet diameter. If the brake could close down behind the bullet as soon as it goes through the first baffle then yes it could effect the velocity. That would really be beneficial to big bores as they allow more gases to escape behind the bullet, due to the bullet diameter, and are less effective. The likelihood of being able to do that with a brake is pretty low and the potential velocity loss wouldn't make it worth while.

 

[Pdvdh]

As J E recommended, unscrew the brake and compare MV to what you had with the brake installed. No simpler way to settle all the discussion as to whether or not the muzzle brake is affecting MV to any extent.

Based on what you've posted so far, I wouldn't leave the MagnetoSpeed unit out the list of possibilities. Fasten your MS to one of your other rifles and confirm the MV is consistent with your prior MVs.

The muzzle brake affecting MV is low on my suspect list of possible causes for the 50fps loss in MV. That's a pretty substantial drop in MV. You might get that much by dropping to a 210 primer, compared to a 215, but you have already verified the correct primer is in use.

 

[Wedgy]

I am going on the record as not volunteering to test the unbraked .338

 

[adrexco]

IdahoCTD
What happens to the velocity if the rifle is held stationary? The law of conservation states that energy is neither lost or created. The energy of the rifle moving is going somewhere. It will either be in the projectile and or gases expelled if the rifle doesn't move. I think a better test would be a load cell to measure pounds force so the rifle doesn't move rather then a slide.

 

[Timber338]

As J E recommended, unscrew the brake and compare MV to what you had with the brake installed. No simpler way to settle all the discussion as to whether or not the muzzle brake is affecting MV to any extent.

Based on what you've posted so far, I wouldn't leave the MagnetoSpeed unit out the list of possibilities. Fasten your MS to one of your other rifles and confirm the MV is consistent with your prior MVs.

The muzzle brake affecting MV is low on my suspect list of possible causes for the 50fps loss in MV. That's a pretty substantial drop in MV. You might get that much by dropping to a 210 primer, compared to a 215, but you have already verified the correct primer is in use.

Thanks for the feedback, I think you know how stubborn I can be at times unfortunately I lack the tools to properly remove and then reinstall my brake and I know I'll also screw up the Cerakote if I try. But I agree this would be the most simple test...

So overall it sounds like it's unlikely to be the brake... What I'm planning is going out and shooting at 600, 800 and 1000 yards using my new muzzle velocity. Then point of impact on the target will tell me if the new muzzle velocity is correct or not.

This close to hunting season I don't have the time to tinker with anything to see how my handloads might be the culprit. Even though I want know the cause of the FPS drop, I'm more motivated to prove out the predictability of my rifle for hunting.

Might not have time to shoot at my long distance range for a couple of weeks, but I'll certainly report the results. Too bad life is so busy!

 

[adrexco]

IdahoCTD
I think a better way to state it is that with your test you are measuring the change in energy by the travel distance of the rifle. So it would make sense that the muzzle velocity would be consistent. The total kenetic energy goes somewhere. If the rifle doesn't move something else has to.

 

[Timber338]

I am going on the record as not volunteering to test the unbraked .338

Hahaha. Smart man.

 

[Timber338]

IdahoCTD
I think a better way to state it is that with your test you are measuring the change in energy by the travel distance of the rifle. So it would make sense that the muzzle velocity would be consistent. The total kenetic energy goes somewhere. If the rifle doesn't move something else has to.

Actually might be on to something that a small change in muzzle velocity might be missed (or absorbed in the system) given that the rifle is moving more/less with different brakes. There are a lot of variables at play here and difficult to understand them all.

 

[IdahoCTD]

IdahoCTD
What happens to the velocity if the rifle is held stationary? The law of conservation states that energy is neither lost or created. The energy of the rifle moving is going somewhere. It will either be in the projectile and or gases expelled if the rifle doesn't move. I think a better test would be a load cell to measure pounds force so the rifle doesn't move rather then a slide.

That would basically be the same as shooting from your shoulder through a chronograph. The velocity doesn't change.

The energy (or gases) that a brake uses to reduce recoil aren't gases that effect the muzzle velocity of a bullet. Those gases flow linear with the bullet and follow the bullet out of the brake untouched. Once that gases deviate from that linear path then a brake redirects them to counter act the recoil.

Yes I could build a set up to measure the force exerted by the rifle and have the rifle not move. Is it going to be any better, not likely, and most people want to see a measurable result rather than a number generated from a pressure pad. Felt recoil can be much different then Ft/lbs of recoil too. The recoil velocity effects felt recoil to a large degree as well.