Muzzle brake clearance
- Thread starter bat119
- Start date
Depends on how true it is to the bore. For 308, I have machined a slightly tapered rod I insert into the muzzle and verify concentricity and clearance. Gunsmith supply shops like PTG and Manson sell rods with interchangeable bushings on 1 10 thou steps to do the same.
I can't understand Sako making a brake for 308 and clearancing it to .390. Doesn't that significantly reduce effectiveness? EDIT: According to tests done by ultimate reloader, excess clearance doesn't have a dramatic effect on the recoil reduction. They tested up to .200 clearance. Interesting.
I can't understand Sako making a brake for 308 and clearancing it to .390. Doesn't that significantly reduce effectiveness? EDIT: According to tests done by ultimate reloader, excess clearance doesn't have a dramatic effect on the recoil reduction. They tested up to .200 clearance. Interesting.
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I'll find somebody to check the opening diameter and alinement before I try it.
Finding a brake 14x1 .366 is not easy only one I can find is from Australia, he does good work although it takes a few months to get the item, at -25 I'm really not in a hurry.
Finding a brake 14x1 .366 is not easy only one I can find is from Australia, he does good work although it takes a few months to get the item, at -25 I'm really not in a hurry.
I made a bunch of 4 inch "spuds" for checking minimum clearance. 2 inches with the diameter turned to slide in the bore freely and the other 2 inches with the diameter turned 20-25 thou over bullet diameter. These spuds were finished turned between centers.
In theory you should be ok but with only .012"/side clearance it would be worth checking. Best to dial the bore in on a lathe then install the brake and take a light cut with a small boring bar to ensure clearance and concentricity. Should be one hour job at most.
You need to specify if that is .020 between the bullet and bore or .020 overall (.010) clearance.
Why not just bore out the brake you have. Its not rocket science to run a drill bit through the brake.
ca. .400 is pretty small to for a boring bar. I had to specially grind my smallest boring bar for the .466" bore required for 1/2-28 threads.
The easier way is to just run a drill through the brake. The drill will follow the bore so fine alignment isn't required. If one has the lathe and tooling then that's the best way, but its not the only way.
FatCatsDad
CGN Ultra frequent flyer
Is there a difference between chucking the brake so it rotates and bringing in a stationary bit and feeding by hand versus chucking the drill bit so it rotates a d feeding in the stationary brake by hand ?
If the brake is true the drill will follow it... if the brake is not true the drill will follow that... it takes a boring bar to correct an untrue brake. You may have to alter or make a boring bar for small diameter boring. I bored as small as .22 caliber brakes.
As little clearance as possible and there shouldn't be an expansion chamber before the "exit hole"
The extra clearance is IMHO to leave room for discrepancies in manufacturing, such as threading and misalignment
All sorts of things happen right after the bullet exits the muzzle when a muzzle brake is attached.
If there is an expansion chamber, it reduces the effectiveness of the brake and keeps the still-expanding propellant gasses closer to the bullet, which creates conditions that "might" have negative effects on it as they quite violently work around it before leaving the muzzle of the brake.
Properly built and attached brakes can make a rifle a pleasure to shoot, or as often happens, create conditions that inhibit good accuracy.
The extra clearance is IMHO to leave room for discrepancies in manufacturing, such as threading and misalignment
All sorts of things happen right after the bullet exits the muzzle when a muzzle brake is attached.
If there is an expansion chamber, it reduces the effectiveness of the brake and keeps the still-expanding propellant gasses closer to the bullet, which creates conditions that "might" have negative effects on it as they quite violently work around it before leaving the muzzle of the brake.
Properly built and attached brakes can make a rifle a pleasure to shoot, or as often happens, create conditions that inhibit good accuracy.
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There are small indexable tools that will handle that quite well. For boring the actual bore of the brake itself there are solid carbide boring bars available (not the brazed carbide ones) in many sizes that cut minimum bores way smaller than we ever need for muzzle brakes. Being carbide for the entire length they are very rigid and cut nicely without chatter. I bore most all of the brakes I install. There is usually at least a wee bit of runout otherwise. It only takes an extra couple of minutes. As guntech said a drill will only follow the runout of the existing hole. They are available at most tool shops and on the internet. I think I bought mine from KBC Tool. I just Googled "micro boring bar" and whole pile show up.
That is an awfully small clearance between bullet and brake. 0.010" doesn't leave any room for carbon buildup or peening or projectile yaw. Such a fine clearance would also require the brake to be final bored to size after being mounted to the barrel.
Probably not. It'd be a lot easier to get the brake straight if it is in a chuck rather than hard mounted to the tool post.
Which requires a lathe and the OP didn't seem to have a lathe ... or he'd likely not be asking such a question.
I probably installed a thousand brakes over the years. I dialed the bore at the muzzle to as close to ten thou as I could in a 4 jaw chuck. Then the barrel was threaded to fit the brake. Then the brake was installed and while in place bored 20 thou (minimum) over bullet diameter up to maybe 30 thou. Brakes can be cleaned, the same as the bore. Bullets are not wobbling when they leave the muzzle. I don't know what you are referring to when you say, "peening".
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I do things the same as Dennis, because that is the right way to do it. I make brakes with an expansion chamber and like them like that. The gases don't buffet the bullet around while they struggle to exit the muzzle. Instead, they simply take the easy way out and exit the side, through holes made for that purpose. I've machined brakes as part of the barrel and these always have an expansion chamber with a restrictor in the muzzle end giving the .020 tolerance. On one I made; the restrictor could be replaced with a liner which effectively turned the brake off.
