Did I hear correctly A broach is used for riffling ?

I would dig seeing this done , Its interesting I have a broach and would not mind learning how this is done . Jess

I think you are referring to button rifling. There are videos of the process online. They are usually pulled, not pushed.

Please let us know if you are successful.

Dan

No, there are plenty of broach rifled barrels out there.

Olympic Arms is one maker.. The Ultra Match models (416 SS) are broached..

It isn't difficult. A broach is pulled through the bore, the barrel has to be drilled and reamed first. After the broaching machine pulls the button through, the better barrel makers send out their barrels to be stress relieved.

Ummm you mean pull the broach through..

Broaching does not induce heavy stress in a barrel, like button rifling does.. In button rifling, the steel is being compressed into shape, not like cut (single groove) or broached (all or multiple grooves cut at same time) rifling..

So... post broach stress relief, would not be as important, as on a button rifled barrel....

The next step up in creating internal barrel stress, would be Autofrettage, Which actually uses interior barrel stress (applied by high pressure hydraulics or a button), to allow thinner lighter cannon tubes (but still durable) to be made...

I knew they broached shorter barrels like pistol barrels, did not realize they did longer barrels. A broach is designed for the length of cut...shorter cut is easier more or less. The chip formed is from the full cut, so for a very long cut you can only take a very tiny amount off.

A broach for a 20 some inch rifle barrel would be a lot longer than one for a 4-6 inch pistol barrel....maybe they use a series of broaches ?

Good conversation here , I will post a pic of my machine . I was thinking a carbide cutter .015 deep would be the bomb for not stressing out the barrel much. here's a video of the first spline I pulled on my machine , its 1 1/2 10 for refrence .

I think you could get make a device that turned the broach with a smaller cut 1/4 turn as it went thru the barrel pretty easily .

Barrels have been broached for years. While its a lot faster than cut rifling the quality of the barrels is not as good as button rifling so it has sort of fallen out of favor over the years for rifle barrels. The cleaner finish of the button rifled barrels outweighs the small amount of stress they have when compared to broached. A lot of pistol barrels are still broached. This video is pretty self explanatory.

Broaching Gun Barrel Rifling - YouTube

That is sweet

Tooling costs would be the killer. Custom broach for every bore size and twist rate.

My (inexperienced) opinion would be that the tooling costs would only be worthwhile if one were making a LOT of same barrels.

Anyone ever have a broach made? What's the cost like compared to a button on a tube?

Cheers
Trev

trevj said:

Tooling costs would be the killer. Custom broach for every bore size and twist rate.

My (inexperienced) opinion would be that the tooling costs would only be worthwhile if one were making a LOT of same barrels.

Anyone ever have a broach made? What's the cost like compared to a button on a tube?

Cheers
Trev

Click to expand...

Buttons are a couple hundred bux. A broach would be a couple thousand I should think. They broach pistol barrels because it's fast, you can't button a thin walled barrel and barrels for Saturday Night Specials don't have to be all that great.

You can always hammer forge. (if you have the big bucks)

BEHIND THE SCENES: DANIEL DEFENSE - YouTube

david n said:

You can always hammer forge. (if you have the big bucks)

BEHIND THE SCENES: DANIEL DEFENSE - YouTube

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I heard TJ's barrel liners are somehow hammer forged, but he uses a carbide mandrel only about 4" long?? Must hammer some, then move it, hammer, move it, etc. He can make a fairly long liner....at least 29" but I seam to recall reading even longer.

abarnsley said:

Ummm you mean pull the broach through..

Broaching does not induce heavy stress in a barrel, like button rifling does.. In button rifling, the steel is being compressed into shape, not like cut (single groove) or broached (all or multiple grooves cut at same time) rifling..

So... post broach stress relief, would not be as important, as on a button rifled barrel....

The next step up in creating internal barrel stress, would be Autofrettage, Which actually uses interior barrel stress (applied by high pressure hydraulics or a button), to allow thinner lighter cannon tubes (but still durable) to be made...

Click to expand...

" being compressed into shape" You mean like work hardened ? How could that be so bad with copper sliding on carbon.
God Bless Harry McGowan and buttons. I made a lit of money betting on single holes and .222

Doooglas said:

" being compressed into shape" You mean like work hardened ? How could that be so bad with copper sliding on carbon.
God Bless Harry McGowan and buttons. I made a lit of money betting on single holes and .222

Click to expand...

Well IMHO the issue with creating stress in the finished product, is what does it do when you warm it up with a shot string ??

Bill

Re compressed into shape..

I am trying to keep things simple..

Simply bending a hacksaw blade back and forth, work hardens the steel until it snaps. Molecules are being compressed and released...

You saw the word autofrettage...

Similar stress is caused by running a button through a rifle bore, bore surface work hardens.. Bores that are button rifled, tend to have a longer accuracy life, than broached..

Yes hammer forging is done with work(barrel) moving over stationary button/mandrel.. A big $$$$ operation..

Stess can be good (as in autofrettage) or bad. Bad stress in a rifle barrel, would be uneven amounts of stress over its length, thus POI changing a barrel heats.

A problem with barrels (especially button rifled) is they are most often rifled as a blank. Then turned to needed profile, this changes the internal stress (and often bore dimensions) to a small degree.

There will never be a 100% perfect stress free, long lasting accuracy, tapered barrel. 99.8% is good enough..

Pedersoli broaches their barrels, then pulls a button through to iron out any imperfections. They have a video of the process up on YouTube.

abarnsley said:

Re compressed into shape..

I am trying to keep things simple..

Simply bending a hacksaw blade back and forth, work hardens the steel until it snaps. Molecules are being compressed and released...

You saw the word autofrettage...

Similar stress is caused by running a button through a rifle bore, bore surface work hardens.. Bores that are button rifled, tend to have a longer accuracy life, than broached..

Yes hammer forging is done with work(barrel) moving over stationary button/mandrel.. A big $$$$ operation..

Stess can be good (as in autofrettage) or bad. Bad stress in a rifle barrel, would be uneven amounts of stress over its length, thus POI changing a barrel heats.

A problem with barrels (especially button rifled) is they are most often rifled as a blank. Then turned to needed profile, this changes the internal stress (and often bore dimensions) to a small degree.

There will never be a 100% perfect stress free, long lasting accuracy, tapered barrel. 99.8% is good enough..

Click to expand...

But one source says that a barrel to be buttoned, is softer than it needs to be if it will be cut rifled.

Bill

Anvil Jenkins said:

But one source says that a barrel to be buttoned, is softer than it needs to be if it will be cut rifled.

Bill

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There are several more factors at play in a barrel.

Firstly, a designer of barrels will be looking for material strength characteristics that allow a barrel to bulge with excessive pressure rather than to undergo brittle failure and shatter. That imediately places a limit on the hardness that a barrel material should have.

second, depending on the use a barrel is intended to have, the hardness at room temperature might not be a very good guide to barrel life. The carbides of iron, loose a significant amount of their strength at little over 100 C, a material which is softer at room temperature but which contains the carbides of alloying elements such as Chromium, molybdenum and vanadium, could very easily be harder at a little over 100 C, and in the case of a machinegun barrel, stellite liners are sometimes used, which are significantly softer than typical steel barrels at room temperature, but which last significantly longer than steel bores.

Swaging a barrel either by forcing a button through it, or by hammer forging it, causes work hardening of the bore, though how beneficial that additional hardness is to barrel life will depend on the composition of the steel used, and what the barrel will be used for; one shot a season or ten thousand in an hour.

The locked in stresses resulting from button or hammer forged rifling can have a very beneficial effect in countering the stresses set up during firing.

The stresses caused by bore heating, also act to counter the stresses of firing and the weakening of the barrel steel by heat. This allows machinegun barrels to be significantly lighter than if they were designed simply taking account of the hot strength of the steel and the stresses imposed by firing. The effects and the maths are described in a paper from the late '60s by Roy e. Rayle, called "Gas Barrel Design" , it's reproduced in Rayle's book "episodes in the life of a weapons developer"

interestingly, with hammer and with button rifling, it is possible to get a slight taper to the bore, high end air gun makers achieve that by turning down the barrel to within a few inches of the muzzle, and leaving the muzzle full thickness. the turned down part of the barrel de stresses and expands slightly, while the bit near the muzzle stays tight.

Of more limited use for accuracy, but still interesting, hard chroming in a bore can be made to taper, by withdrawing the barrel from the plating tank slowly, so a slightly greater thickness of chrome is deposited near the muzzle.