Barrel Cutting...

[bobgengeskahn]

So I've decided to cut the barrel on my 180 series mini. Is there any consensus on what is the ideal lenght? I've read everything from 13" to increments between 15" and 16". Any advice?

[my1911s]

In theory, the shorter the barrel the stiffer it becomes and a stiff barrel is more accurate due to reduced harmonic vibration. Shorter barrels also reduce velocity, leaving a less effective cartridge. To be legal the barrel must be 16” minimum, which can be achieved by “permanently” attaching a comp or flash hider to a shorter barrel to bring it to 16”. The attachment method must meet ATF regs.

On my rifle I chose 16 5/16” because my muzzle bottomed in my Choate flash hider just as my flash hider reached the barrel step. This was the best thing I’ve done to this rifle, it should have been made with a 16” tube in the first place.

[rutro]

Bobgengeskahn if you are certain you want to shorten that barrel then this is something to read, http://www.perfectunion.com/vb/showthread.php?t=51631&highlight=where+to+cut+barrel. Whatever you decide to do I hope it works out for ya!!!

[Jaybird]

If it were me, I would ask the Gundoc. He has probably cut down more barrels to different lengths than most and can probably tell you what would work, along with degree of crown, threading, etc. He cut mine down and it shoots better than I can. I don't remember the length or I would tell you. The Smith brake he installed helps also. Besides, he is friendly and will "GIVE" you the advice.

[bobgengeskahn]

Thanks for the posts! Ruto, That post was actually the one that got me thinking about cutting my barrel in the first palce. Where would I be able to find acceptable methods for attaching a break, per ATF standards?

[fire for effect]

In theory, the shorter the barrel the stiffer it becomes and a stiff barrel is more accurate due to reduced harmonic vibration. .

This is not correct. Increasing stiffness does not reduce Harmonic Vibration. Increasing Stiffness raises the frequency at which Harmonic Vibration takes place. Increasing the Mass reduces the frequency at which Harmonic vibration takes place. It would be best that when shooting, the barrel is not in harmonic resonance, but this can be corrested any number of ways. Changing the impulse whch creates the Reasonance, (change your load) Adding barrel weights, (increasing mass).

[rutro]

Bobgengeskahn silver solder seems to be the method of choice. ATF says it must be permenant to be legal and a high melting temp silver solder is probably the easiest way to meet that requirement. I looked into that at one time and to do it right you dang near need an acetelyne torch to get the heat needed. I never did any measureing, how long is the barrel there at the step?

[my1911s]

fire for effect

Sorry to disagree with you but stiffer barrels do decrease harmonic oscillation. That is the point behind carbon fiber barrels, increasing rigidity without increasing mass. About two years I began tuning my Mini barrel with weights. With 100 grams of elastomer isolated weight behind a heavy flash hider the accuracy improved greatly. I did not like the look or the feel so I cut the barrel by 2 3/16” and installed a much lighter Choate flash hider. The accuracy was better than with weights and the look and feel was just what I was looking for.

[fire for effect]

fire for effect

Sorry to disagree with you but stiffer barrels do decrease harmonic oscillation. That is the point behind carbon fiber barrels, increasing rigidity without increasing mass. About two years I began tuning my Mini barrel with weights. With 100 grams of elastomer isolated weight behind a heavy flash hider the accuracy improved greatly. I did not like the look or the feel so I cut the barrel by 2 3/16” and installed a much lighter Choate flash hider. The accuracy was better than with weights and the look and feel was just what I was looking for.


You can disagree with me all you want but the Physics backs me up. Increasing Stiffness increases the Frequency (in Hertz)of resonant Vibration. Increasing Mass Decreases Frequency (also in Hertz) of Resonant Vibration. The Resonant Vibration still exists, but at a different frequency. Increasing stiffness, or increasing mass, is like changing the pitch of a bell, It still rings, just a different note. I have been in the business of Vibration, and vibration analysis since 1977, being trained at the University Of Iowa, the University of Wisconsin, and International Research and Design.

[my1911s]

I’ve cut the barrel and improved accuracy on more than one gun, so I know it works. Frequency is one thing, amplitude is another, and stiffer barrels reduce amplitude which reduces the movement of the muzzle in relation to the node. I’m impressed with your credentials but I’m the one with the hack saw, give it a try before you say it can’t work. You can listen to some liberal professor all day long but until you’ve actually put your hands on something you’re just giving your opinion. You know what they say about opinions.

[fire for effect]

You really need to re-read what you wrote and re-read what I wrote. I did not say that it does not work, I said that your statement, about stiffness and resonant frequency is not correct. You do not eliminate Resonance by increasing stiffness, you are simply increasing the frequency in hertz, or cycles per second, at which it occurs. The resonance will still be there but it will take energy at a different frequency to excite it. Amplitude is simply a function of the amount of energy input at the resonant frequency.

[my1911s]

Forgive me but I don’t recall using the term “resonant frequency”, for one thing, I lack the mental aptitude to understand such a concept. What I said was “stiffer barrels reduce harmonic oscillations”, meaning the muzzle center deviates a lesser degree from the node. In addition to shortening barrels for increased rigidity, barrel fluting is also used in the BR community to accomplish the same effect. They have found that a round barrel is less rigid that a fluted barrel of the same mass and consequently the latter being more precise with regard to random variation in grouping. I agree that a stiffer barrel would increase frequency but at a lower amplitude, meaning less muzzle movement.
Having said that, I bow to your expertise.

[Texas Patriot]

I'm gonna side-step the physics debate on barrel resonance and say that Gun Doc cut my barrel to 15" and installed a fh to make it 16+" overall. I've got it in a butler creek folder and love it. It is my favorite gun to go shooting with now. Also have a Bushnell Holosite sitting on an Ultimak rail. Really cool and accurate gun.

[fire for effect]

Harmonics are resonances. With regard to barrel fluting. If you take two barrels of the same size and weight, they have the same stiffness, and the same mass. Now if you flute the barrel you are reducing its mass, thereby increasing the frequency at which the barrel resonates. It is technically not getting stiffer, because it has the same stiffness as the unfluted barrel. It does weigh less and therefore has less mass. As stated in a previous post, Less Mass causes a Higher resonate frequency. More mass causes a lower resonate frequency. The second benefit of fluted barrels is the fact that the fluting increases the surface area of the barrel, which allows it to cool faster. As a barrel heats up it gets longer. If you think of the end of the barrel vibrating over time, it will produce a sine wave. Imagine the bullet leaving the muzzle as it vibrates. As long as the bullet leaves the muzzle at the same point on the sine wave it will hit the target in the same place. Now since steel expands as it heats up at a constant rate per degree, per inch, you will notice that the barrel actually gets longer as it gets hotter. This means that the bullet will be leaving the muzzle at a different point in the sine wave, and hitting the target in a different place. The muzzle is actually pointing in a different direction, if however minutely.

[my1911s]

No, round barrel = x mass, fluted barrel = x mass after fluting. Same weight, fluted is stiffer. Look it up.

[bobgengeskahn]

Patriot-
what series is your mini? That is actually the same set-up I am looking at. I have an Ultimak on there and now am just searching for an optic. I would like to get a folder, however until I move out of Cali that is not an option so Im just looking at different synthetic stocks for now. how much did your groups improve after the drop to 15" and what kind of break did the doc put on there?

[Texas Patriot]

Patriot-
what series is your mini? That is actually the same set-up I am looking at. I have an Ultimak on there and now am just searching for an optic. I would like to get a folder, however until I move out of Cali that is not an option so Im just looking at different synthetic stocks for now. how much did your groups improve after the drop to 15" and what kind of break did the doc put on there?

Mine is a 196 series ss regular model. I used a Choate fh front sight combo. I chose the black version of the Choate on my ss barrel for contrast and I think it looks really good. This also forced me to change the rear sight aperture, which I got from Ruger. The old sight did not work with the new front sight, so I needed an aperture that was drilled lower in the rear sight blade.
My new groups are probably about 1-1.5" at 50 yards shooting with the Holosite or open sights. Don't think I've tried it at 100 yards since the chop job. But with this set up, there is Zero recoil. My daughter loves to shoot this gun now since it is so compact with no recoil and its accurate. She also likes the Holosite set up.

[fire for effect]

No, round barrel = x mass, fluted barrel = x mass after fluting. Same weight, fluted is stiffer. Look it up.

You really need to read more carefully. What you have stated is not what I described in my previous post.

With regard to barrel fluting. If you take two barrels of the same size and weight, they have the same stiffness, and the same mass. Now if you flute one barrel you are reducing its mass, thereby increasing the frequency at which the barrel resonates. It is technically not getting stiffer, because it has the same stiffness as the unfluted barrel. It does weigh less and therefore has less mass. As stated in a previous post, Less Mass causes a Higher resonate frequency. More mass causes a lower resonate frequency.

A fluted barrel will have more stiffness then an unfluted barrel of the same weight and length, but this is not what I was describing in my text. Perhaps the misunderstanding is because I wrote, "Flute the Barrel". rather than "flute one Barrel".

[mini-mizer]

You can disagree with me all you want but the Physics backs me up. Increasing Stiffness increases the Frequency (in Hertz)of resonant Vibration. Increasing Mass Decreases Frequency (also in Hertz) of Resonant Vibration. The Resonant Vibration still exists, but at a different frequency. Increasing stiffness, or increasing mass, is like changing the pitch of a bell, It still rings, just a different note. I have been in the business of Vibration, and vibration analysis since 1977, being trained at the University Of Iowa, the University of Wisconsin, and International Research and Design.

Fire For Effect: I appreciate your input and sharing your knowledge regarding this subject here on the board.

I've done a bit of experimenting with the mini14,
and have had good results in getting good field accuracy from
mine via adding a BOSS type tuner and also in shortening the barrel
and adding a shop made tuner (sort of a bloop tube).


Would you please explain how the vibrations travel up and down the barrel and at
what speed they travel, interact with each other, ect.

Also the end of the new target model had a series of grooves machined into the muzzle (there's a photo
link off of another post). Any thought on those?

I have experimented in adding different sized weights and have found that size, shape, &
length all make a difference in the way the rifle groups. There seems to be a certain design that yields the best result, not just
bigger is better.

Tnks MM

[fire for effect]

No, round barrel = x mass, fluted barrel = x mass after fluting. Same weight, fluted is stiffer. Look it up.


Fluting is a reduction process. you are removing mass to create the flutes in the Barrel. So if the finished product has the same mass as an unfluted barrel, then the fluted barrel had to have more mass then the unfluted barrel before the fluting process took place.
IN other words, the fluted barrel had to have more mass and stiffness then the round barrel to begin with, so that after fluting the mass was the same, but the greater stiffness remained. Is that understandable??

[fire for effect]

Fire For Effect: I appreciate your input and sharing your knowledge regarding this subject here on the board.

I've done a bit of experimenting with the mini14,
and have had good results in getting good field accuracy from
mine via adding a BOSS type tuner and also in shortening the barrel
and adding a shop made tuner (sort of a bloop tube).


Would you please explain how the vibrations travel up and down the barrel and at
what speed they travel, interact with each other, ect.

Also the end of the new target model had a series of grooves machined into the muzzle (there's a photo
link off of another post). Any thought on those?

I have experimented in adding different sized weights and have found that size, shape, &
length all make a difference in the way the rifle groups. There seems to be a certain design that yields the best result, not just
bigger is better.

Tnks MM The vibrations travel at an instantaneous speed, since the molecules of the steel are in contact with each other. an example would be the feeling in your hand when you strike an anvil with a hammer. The problem I see with the mini 14 is that the Barrel is held rigidly by the receiver and the gas block, but the remainder of the barrel is vibrating like a bell. We all know that a free floating barrel is generally much better because it allows the entire barrel to vibrate naturally. This is hard to do with the Mini 14, so the other solution ha been to increase the barrel diameter past the gas block to change its resonance.

[Marlin 45 carbine]

Sounds like you know of what you speak, for what it is worth I have free-floated my M-30 barrel (floated the gas-block) and tightly shimmed the receiver/stock/trigger group lock-up. Haven't been to the range with it and can't make it for at least couple more weeks due to work requirements but will post findings. Oh yeah, have to load some rounds to try out also.

[my1911s]

mini-mizer
In answer to your question, I would offer the following:

http://www.rifle-accuracy.com/harmonics.htm

or

http://www.snipersparadise.com/tsmag/may2005.htm

for a slightly different take

http://www.precisionshooting.com/psm_2005_03_issue.html

[mini-mizer]

1911----Thanks for the links, outstanding information, that
answers it all and then some..
Regards MM