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Indexing a brake
- Thread starter Matt P
- Start date
Butch Lambert
Active member
28TPI means it moves 1" for 28 turns. I think ea. turn is .0393". If you need a quarter turn machine the barrel shoulder about .010". The shoulder that I'm speakinof is where the brake stops on the barrel.
Butch
Butch
D
Dennis Sorensen
Guest
Divide 1" by 28 = .0357" to a full turn.
Divided by 4 = .0089" to a quarter turn.
Divided by 8 = .0045" to one eighth turn.
First thread and screw the brake up tight... Inspect and make sure it is shouldered and not bottomed on threads. Then measure and remove slightly less than required to index it and re-install and tighten on the shoulder. Inspect and make very small adjustments working it back and forth until it is indexed and tight. Many will then take it off and add Loctite and tighten to the indexed point.
Divided by 4 = .0089" to a quarter turn.
Divided by 8 = .0045" to one eighth turn.
First thread and screw the brake up tight... Inspect and make sure it is shouldered and not bottomed on threads. Then measure and remove slightly less than required to index it and re-install and tighten on the shoulder. Inspect and make very small adjustments working it back and forth until it is indexed and tight. Many will then take it off and add Loctite and tighten to the indexed point.
Butch Lambert
Active member
I guess I need to quit doing math in my head. I was .0036" off. Glad you have a calculator Dennis.
Butch
Butch
J
Jkob
Guest
Here is the way I do it and recently put one on a 7mm lapua mag for a client. It was 24 tpi. one divided by 24 = .0417 divied by 360 = .000116, the amount for one degree. Next, I level the action and with the brake screwed on, measure the amount of turn needed, in degrees, to get it to orient correctly. I use a bubble protractor for this. Multiply the number of degrees times the .000116 to get the amount needed to take off either the barrel shoulder or the brake. Say 22 degrees needed, 22 times .000116 =.0028. Small amount and easy to take too much. My math may be wrong but I think you get the idea.
C
CGS
Guest
How do you feel about the use of peel washers? It's not as "pretty" of an install but it gets the job done. especially useful if you don't have a lathe.
How do you feel about the use of peel washers? It's not as "pretty" of an install but it gets the job done. especially useful if you don't have a lathe.
ONLY if you don't have a lathe...........OK for AR15 and AK47 type rifles, but shouldn't be on a fine BR or hunting rifle.
My research has found that SOME indexable muzzle brakes will hurt accuracy. I contend that those brakes that have no holes on the bottom, but holes on side and top, set up strange air resistance in front of the bullet as it exits.
The most accurate brakes I've experimented with have hole all around the brake. And if they are spiral they require zero indexing...........
Article on my web page.... www.rvbprecision.com
D
Dennis Sorensen
Guest
Roy,
If you cut and pasted the text from your article into the thread it would be so much better than having to try and find it searching through your web page.
If you cut and pasted the text from your article into the thread it would be so much better than having to try and find it searching through your web page.
Sorry, there is a lot of stuff on that site now. My son added a Table of Contents at the top that does make it a bit easier to navigate.
Here is a direct link to the MB article
http://rvbprecision.com/shooting/adventures-with-muzzle-brakes.html
Here is a direct link to the MB article
http://rvbprecision.com/shooting/adventures-with-muzzle-brakes.html
D
Dennis Sorensen
Guest
Copied and pasted...
A couple of years ago I got involved with brake development and
experimentation. This was purely for my own edification. I’m just a
hobbiest and needed something to do!
I bought a brand new Savage 112 in 308 with laminated stock and SS
fluted barrel to be used as a test bed. I threaded the barrel to 1/2-28.
This is the thread that most brakes are available in since it is the
standard AR-15 thread. I would be testing aftermarket available brakes
along with my own designs. I made a rifle rest that would allow the
rifle to recoil and the amount of recoil to be measured. I tried to set
up a scale to measure this recoil force, but it was inconclusive. I
made over a dozen brakes for this rifle. All different size port holes
from many, many small holes to just two huge holes on either side (sort
of like a military tank compensator). I would start out with the exit
hole a very few thousands over bullet diameter and ream it out in .005″
steps, testing between each enlargement. I tried different lengths. How
long is too long? Different materials. Different hole spacing and
location. Here is what I found….
Exit Hole- If the exit hole is too small, ie <.005″ over bullet
diameter, accuracy suffers. Accuracy really suffers if the exit hole is
more than .25″ deep. The depth of the exit hole creates a “tube” the
bullet must pass through on its way to the target. If the depth of the
exit hole is too shallow the metal around the hole will erode very
quickly. There is not much heat and pressure (5000psi) at the muzzle,
but over time a thin piece of any metal will fail.If the hole is too
small, I believe it is the air trying to get by the bullet that upsets
flight. Best accuracy and effectiveness of the brake was obtained with
.020″ over bullet diameter. There was no measurable reduction in recoil
between .005 and .020. Measurable change in recoil happened at .040″
over bullet diameter. Any exit hole over .040 and the brake began to
lose effectiveness rapidly.
Holes- Most effective braking was with a
brake 1″ in diameter with a 3/4″ exit hole on each side, just infront of
the muzzle. The bullet passes through a cone of 35 degrees before it
exits the brake. (Like the tank example), Incredible reduction of
recoil. But loud and ugly. Very easy to make since you don’t need a spin
fixture or a dividing head. As far as individual holes, it make no
difference the diameter or amount as long as they are large enough and
plenty enough to bleed off all the gas trapped in the brake. I’ve built
brakes with 48 – 1/8″ holes and 30 – 3/16″ holes and they both work
identical. I’ve drilled the holes completely random around the brake
(looks like hell!) and in straight patterns and helix patterns….no
difference on accuracy or reduction. I now use a left to right helix of
3/16″ holes .010″ apart at a 2 degree off set. A total of 5 holes in a
row, six rows for a total of 30 holes. The brake ends up at 2 3/4″ with
a 1/2″ thread depth for an overall extension of the barrel of 2 1/4″.
The helix keeps the brake tight and it doesn’t need to be indexed. If
the brake is indexed so the holes line up with the barrel, after
removing it a few times the holes will shift a few degrees and look less
than professional.
Material- I’ve made them of Stainless, CM, and
Aluminum…No difference at all. The Aluminum brakes harden somehow
after repeated firring and I have one on an AR-15 with over 12,500
rounds (Moly test gun) and the brake is perfect.
Holes on top only- In
my tests, not having holes all around the brake effects accuracy a bit.
I believe it does something to the bullet by the air pushed ahead of the
bullet creating unequal turbulence in the bullet path. I’ve tried a few
brakes where I drilled only holes on the top, test fired, and then
completed holes on the bottom and in every case, accuracy improved. Put
an old blanket down if you don;t want to kick up dust in the prone
position.
Expansion Chamber- A brake bored out to thread diameter
right up to the exit hole is much more effective than a brake where the
bore is exit hole for the full length, Having the bullet traverse this
large expansion area somehow improves accuracy and there is a marked
reduction of recoil.
Effectiveness- The higher the pressure of the
particular round, the more effective the brake. I have over 20 rifles
with brakes. The 220 Swift is the king of reduction. Followed very
closely by the 25-06, 6mmRemington, any Weatherby small bore. With a
proper brake and a hot handload under a 40 gr bullet, the Swift will
move 1/2″ to the rear and 0 muzzle rise! Big boomers with low pressure
like 45-70s and shot guns benefit the least. I have two identical
Remington 700s both with identical brakes. One in 308 and the other in
300 Win Mag. Both shooting 155 Sierra Palma bullets, the Win Mag about
300FPS faster, and the Win Mag has measurably less recoil! Must be the
pressure / amount of gas available.
Length- After 3″ there isn’t enough
gas left to do anything. The longer the brake, the harder it is to hold
concentricity of bore exit hole. If the exit hole isn’t +-.0005″ ,
accuracy will suffer.
A couple of years ago I got involved with brake development and
experimentation. This was purely for my own edification. I’m just a
hobbiest and needed something to do!
I bought a brand new Savage 112 in 308 with laminated stock and SS
fluted barrel to be used as a test bed. I threaded the barrel to 1/2-28.
This is the thread that most brakes are available in since it is the
standard AR-15 thread. I would be testing aftermarket available brakes
along with my own designs. I made a rifle rest that would allow the
rifle to recoil and the amount of recoil to be measured. I tried to set
up a scale to measure this recoil force, but it was inconclusive. I
made over a dozen brakes for this rifle. All different size port holes
from many, many small holes to just two huge holes on either side (sort
of like a military tank compensator). I would start out with the exit
hole a very few thousands over bullet diameter and ream it out in .005″
steps, testing between each enlargement. I tried different lengths. How
long is too long? Different materials. Different hole spacing and
location. Here is what I found….
Exit Hole- If the exit hole is too small, ie <.005″ over bullet
diameter, accuracy suffers. Accuracy really suffers if the exit hole is
more than .25″ deep. The depth of the exit hole creates a “tube” the
bullet must pass through on its way to the target. If the depth of the
exit hole is too shallow the metal around the hole will erode very
quickly. There is not much heat and pressure (5000psi) at the muzzle,
but over time a thin piece of any metal will fail.If the hole is too
small, I believe it is the air trying to get by the bullet that upsets
flight. Best accuracy and effectiveness of the brake was obtained with
.020″ over bullet diameter. There was no measurable reduction in recoil
between .005 and .020. Measurable change in recoil happened at .040″
over bullet diameter. Any exit hole over .040 and the brake began to
lose effectiveness rapidly.
Holes- Most effective braking was with a
brake 1″ in diameter with a 3/4″ exit hole on each side, just infront of
the muzzle. The bullet passes through a cone of 35 degrees before it
exits the brake. (Like the tank example), Incredible reduction of
recoil. But loud and ugly. Very easy to make since you don’t need a spin
fixture or a dividing head. As far as individual holes, it make no
difference the diameter or amount as long as they are large enough and
plenty enough to bleed off all the gas trapped in the brake. I’ve built
brakes with 48 – 1/8″ holes and 30 – 3/16″ holes and they both work
identical. I’ve drilled the holes completely random around the brake
(looks like hell!) and in straight patterns and helix patterns….no
difference on accuracy or reduction. I now use a left to right helix of
3/16″ holes .010″ apart at a 2 degree off set. A total of 5 holes in a
row, six rows for a total of 30 holes. The brake ends up at 2 3/4″ with
a 1/2″ thread depth for an overall extension of the barrel of 2 1/4″.
The helix keeps the brake tight and it doesn’t need to be indexed. If
the brake is indexed so the holes line up with the barrel, after
removing it a few times the holes will shift a few degrees and look less
than professional.
Material- I’ve made them of Stainless, CM, and
Aluminum…No difference at all. The Aluminum brakes harden somehow
after repeated firring and I have one on an AR-15 with over 12,500
rounds (Moly test gun) and the brake is perfect.
Holes on top only- In
my tests, not having holes all around the brake effects accuracy a bit.
I believe it does something to the bullet by the air pushed ahead of the
bullet creating unequal turbulence in the bullet path. I’ve tried a few
brakes where I drilled only holes on the top, test fired, and then
completed holes on the bottom and in every case, accuracy improved. Put
an old blanket down if you don;t want to kick up dust in the prone
position.
Expansion Chamber- A brake bored out to thread diameter
right up to the exit hole is much more effective than a brake where the
bore is exit hole for the full length, Having the bullet traverse this
large expansion area somehow improves accuracy and there is a marked
reduction of recoil.
Effectiveness- The higher the pressure of the
particular round, the more effective the brake. I have over 20 rifles
with brakes. The 220 Swift is the king of reduction. Followed very
closely by the 25-06, 6mmRemington, any Weatherby small bore. With a
proper brake and a hot handload under a 40 gr bullet, the Swift will
move 1/2″ to the rear and 0 muzzle rise! Big boomers with low pressure
like 45-70s and shot guns benefit the least. I have two identical
Remington 700s both with identical brakes. One in 308 and the other in
300 Win Mag. Both shooting 155 Sierra Palma bullets, the Win Mag about
300FPS faster, and the Win Mag has measurably less recoil! Must be the
pressure / amount of gas available.
Length- After 3″ there isn’t enough
gas left to do anything. The longer the brake, the harder it is to hold
concentricity of bore exit hole. If the exit hole isn’t +-.0005″ ,
accuracy will suffer.
C
Chip Soles
Guest
Hi Dennis,
WOW! That is a lot of work, and data to gather. This is probably the most informative piece, that I, have read on this subject. Thank you. Did the "best" brake, improve upon the initial accuracy, of any of the test rifles, or was the main benefit, recoil reduction?
Regards,
Bob
WOW! That is a lot of work, and data to gather. This is probably the most informative piece, that I, have read on this subject. Thank you. Did the "best" brake, improve upon the initial accuracy, of any of the test rifles, or was the main benefit, recoil reduction?
Regards,
Bob
dennisinaz
New member
Not having the time nor resources to make all those test models, I blatantly plagiarized the design used by the Apache helicopters (plant is 3 miles from my house). I have a friend that works in an aerospace shop and he had a lot of down time. I just gave him barrel drops and a blueprint. He made a number of brakes for me; most of them went on 300 Weatherby chambered rifles.
The design we settled on is a straight cylinder about .7" diameter. We drilled either 2 or 3, 1/2" holes all the way through. The brake is timed so that the holes are at 3 and 9 o'clock. The exit hole is reamed with a chucking reamer to .015" over bullet diameter.
This design proved to be very effective at recoil reduction and doesn't blow out the bottom. When hunting from a prone position, a brake with holes all the way around is a very big handicap. Another downside is that you cannot shoot them off the hood of your truck.
As for making them from Aluminum, a local gunsmith in town made a few on request and all them them have blown up to date (300 RUM chambered rifles) I think if you want to use Al, you need to make them much beefier than a steel or Ti brake.
I don't currently have any brakes on any of my rifles as they are simply too noisy to shoot a rifle such equipped without hearing protection. For big game hunting, this is a deal killer.
The design we settled on is a straight cylinder about .7" diameter. We drilled either 2 or 3, 1/2" holes all the way through. The brake is timed so that the holes are at 3 and 9 o'clock. The exit hole is reamed with a chucking reamer to .015" over bullet diameter.
This design proved to be very effective at recoil reduction and doesn't blow out the bottom. When hunting from a prone position, a brake with holes all the way around is a very big handicap. Another downside is that you cannot shoot them off the hood of your truck.
As for making them from Aluminum, a local gunsmith in town made a few on request and all them them have blown up to date (300 RUM chambered rifles) I think if you want to use Al, you need to make them much beefier than a steel or Ti brake.
I don't currently have any brakes on any of my rifles as they are simply too noisy to shoot a rifle such equipped without hearing protection. For big game hunting, this is a deal killer.