Effects of "tunneling" on muzzle brake?

[CCM]

I read every now and then in the suppressor world about "tunneling" where the bore in a baffle is too long and can impart instability on the bullet. I can't find much outside information on the subject so I can't speak to it's legitimacy. It did, however, get me thinking about my shop brake design. It's essentially just a tunnel bored .02" over bullet diameter with ports drilled at 80⁰ to the bore. It's not a full radial as there are no ports top or bottom. I haven't experienced any accuracy issues thus far with it but I'm wondering if I should modify the design a bit? Most of the commercial brakes I see are drilled out to the thread minor diameter until at least the first baffle.
I'm leaning toward the train of thought of if it ain't broke don't fix it..

 

[gunsandgunsmithing]

Your brake looks good. From personal experience with a lot of brakes, I'd not worry about whatever tunneling is. Sounds like a solution looking for a problem to me.

 

[JMayo]

Gunsandgunsmithing knows guns. It's safe to Listen to him !

 

[DaveTooley]

I found that if you have an internal expansion chamber that length is critical. Anything longer than 1"-1.25" will allow gas to pass the bullet upsetting it. Even with a tight bore, +.020"- +040" over bullet diameter there's no need for a long brake. The first port does 80% of the work. Expansion chamber type brakes are a bit more efficient but we're talking minor differences between the different styles. When I make brakes like yours I have an expansion chamber but keep them short. And it's OK to have holes on top as well. I made many that didn't have holes on the bottom for varmint hunting and it had no affect on accuracy.

 

[CCM]

Your brake looks good. From personal experience with a lot of brakes, I'd not worry about whatever tunneling is. Sounds like a solution looking for a problem to me.

Thank you. That's the direction I've been leaning as well.

I found that if you have an internal expansion chamber that length is critical. Anything longer than 1"-1.25" will allow gas to pass the bullet upsetting it. Even with a tight bore, +.020"- +040" over bullet diameter there's no need for a long brake. The first port does 80% of the work. Expansion chamber type brakes are a bit more efficient but we're talking minor differences between the different styles. When I make brakes like yours I have an expansion chamber but keep them short. And it's OK to have holes on top as well. I made many that didn't have holes on the bottom for varmint hunting and it had no affect on accuracy.

I can see where an expansion chamber is more efficient, do you increase the diameter of the brake to keep up wall thickness/ surface area for the gasses to act on?

I've also built baffle brakes for large bore rifles that work amazingly well but they're a little violent on concussion.

 

[DaveTooley]

Thank you. That's the direction I've been leaning as well.


I can see where an expansion chamber is more efficient, do you increase the diameter of the brake to keep up wall thickness/ surface area for the gasses to act on?

I've also built baffle brakes for large bore rifles that work amazingly well but they're a little violent on concussion.

View attachment 1447370

You can get away with pretty thin walls as pressure drops quickly. I always used the tap drill size for the chamber. Quicker and lazier.
Now to give away some trade secrets. Muzzle blast. On radial brakes I angle the holes 5 degrees forward. No complaints about recoil reduction. On your baffle brake go to the inside of the closest edge to the muzzle and put a chamfer on it. It will direct a small amount of gas and keep the concussion out front. you can even put a small angle on the bottom to reduce muzzle jump.

 

[gunsandgunsmithing]

I've made and used a bunch of different designs and they all work. Measuring the performance difference is one thing and companies justifiably use this testing to tout their design as being best or better than others etc. But feeling the difference is a lot different than having a pretty substantial difference...measured vs what you can actually feel. I believe sail area is the biggest thing, next is location of that first baffle. I read a military test report several years back on this subject and it concluded that about 1 inch in front of the crown was where the sweet spot is on small arms in regard to where the back edge of the first baffle is. I tested that a fair bit and I agree with it.

Expansion chambers and exit hole diameter etc matters a small bit too but I don't think I can "feel" the difference in those things when kept in the right size range for the hole diameter and expansion chamber size.

Brakes are pretty amazing devices and can turn a 300 mag into a 30-30 or similar in terms of recoil. Of course this comes at a price, being noise level. I've read, and it makes sense, that the actual decible level stays the same. But sound travels through air and instead of the muzzle blast pushing the sound straight away from you, a brake dumps it laterally or slightly toward the shooter. The perceived difference is pretty huge. That little bit of "rocket effect" makes a big difference in how loud it seems but is only a small part of how a brake works. A brake literally pulls the gun forward. It's those gasses working on the sail area that does the real work. The other details get lost in the noise. Pun intended there. Lol! The run and gun guys, like USPSA 3 gun shooters benefit from a good brake that most of us. That game is all about speed and target re-aquistion. I've toyed with timing them to counter torque etc, too. Every little bit matters in that game but it takes a lot of effort to be able to tell the difference in the very best and just a run of the mill brake...IME.

When doing some measuring of brake performance, I made a brake that was actually better than by far, most brakes out there. It was simple, crude and kinda ugly but it was very effective. It was a 1 inch od piece of bbl cutoff and I put a .500 hole perpendicular to the bore with the front edge of the hole 1 inch in front of the crown and it was reamed .018 over bullet diameter...only ONE baffle. It tested better than some expensive aftermarket brakes. It was actually amongst the very best, believe it or not. It surprised me how well it did against the others. My intention was only to use it as a baseline against which all the others were to be compared. Goes to show the importance of that first baffle, it's area and location vs all the other smoke and mirror stuff.

I also did a few for handguns using a 5 axis cnc where I could go in and scallop the baffles inward to kinda form a cup around the bore, just to make them as effective as possible. Those were fantastic but expensive to make and very time consuming.

Bottom line though, they all work and I wouldn't get too caught up in all the details and pay a lot for those things, myself, on most any hunting or br type of rifle unless you just have too much money. Lol! The difference between a $30(at the time) Harrell's vs a $300 brake was hard to feel but it did measure quite differently.

 

[Steel Mover]

This is my 26" 45-70 Mauser with my counter bored reamer cut integral break, the ports of 2", it only shoots sub 1/2 inch. You do not just run a hand drill nto the muzzle. PTG sells counter bore reamers that are guided with internal crowns, like this barrel has. This one has a recessed target crown cut.