Observation (likely not new) about muzzle brakes?

[ntsqd]

J E's post quoted partly truncated below from this thread: https://www.longrangehunting.com/threads/anybody-put-a-boss-on-a-custom-barrel.238022/ got me to thinking. When the bullet is moving down the barrel there is a column of air moving in front of it. Granted, it's not nearly as hot and expanding as the combustion gases behind the bullet, but since its moving down the bore ahead of the bullet at something close to the bullet's velocity I wonder how much effect it is having on recoil reduction before the bullet reaches the brake? I'm not expecting that it is a huge contribution, but I wonder if it is enough to be significant?

To a small degree they actually start working because some of the powder charge exits with the bullet but before it has enough effect on the bullet to effect the accuracy. the lower the recoil, the lower the harmonics/vibrations, and the less they effect accuracy. Normally the greatest improvement is shooter skill because he can concentrate on better trigger control and position, because he is not anticipating the recoil and flinching. The efficiency of muzzle brakes depend on many design factors. that Is the reason there is such a difference if muzzle brake performance.
........

J E CUSTOM

 

[rammac]

No.
The column of air in front of the bullet does not reduce recoil, it adds to the recoil but it's insignicant and isn't considered by anybody when they calculate recoil.

 

[ntsqd]

Presumably that column of air will act on the brake the same as the driving gases, just not with the energy that the hot gases have.

 

[rammac]

Lets put it this way, the column of air in front of a 168 grain, .308 Win bullet, fired from a 22 inch barrel, will produce about 0.5 inch pounds of recoil which is about 0.24% (a little more than 2 tenths of a percent) of the total force of recoil - so I don't think that it really matters.

Yes, I did the math using my QuickLoad software for the recoil data and simple estimates using the volume of the bore and how much mass air has per volume.

What's more, the actual force of recoil will probably be a little less since these are estimates using the total volume of the bore while in actuality the air column gets smaller as the bullet moves down the bore and gains momentum. My guess is that the column of air in front of the bullet for the last few inches will be the only air that has enough velocity to actually produce a measurable recoil force.

 

[ntsqd]

That last portion of travel is probably also the only portion where the pressure of that air is significant enough to impart any force on the brake, further reducing it's impact on recoil. Sum zero game or nearly so.

 

[Bart B]

Gas behind the bullet upon leaving the muzzle has a velocity a few times faster than the bullet. It will bounce off the muzzle brake and some will be deflected back onto the bullet while it's still in the brake. Hopefully evenly around the bullet without degrading accuracy.

The flash suppressor on M14 7.62 NATO service rifles was also used on the national match versions. Shooting the original M14NM in the rain soon revealed the supressor's bore diameter was too small. Bullets deflected off rain drops inside the supressor degrading accuracy. All the M14NM flash suppressors got reamed out.

Muzzle brakes need clearance too.