Threading a barrel and its effects on accuracy

[DRM6000]

Would threading a barrel affect the rifle's accuracy? I have a precision rifle that shoots great (~0.25MOA), but I was thinking about threading the barrel to accept a muzzle device. Also, would a thread protector affect accuracy?

I understand that there will be a POA/POI shift with a muzzle device, but what is the likelihood of the rifle maintaining its accuracy?

[RobG]

If done correctly it should have zero impact on accuracy. The brake may or may not shift your POI.

[Fjold]

Any machining or change to a barrel can effect accuracy. You don't know the result until you do it though.

[FourT6and2]

I've read that it won't affect "accuracy" per se. But adding weight, reducing weight, adding length, or reducing length to your barrel can affect how the barrel vibrates. The barrel is a giant tuning fork that vibrates at a specific frequency for a given load. And every object (not just a barrel) has a resonant frequency at which it vibrates and resonates with the most ease. The reason people do load work ups to find an accuracy node is to find that resonant peak at which the barrel vibrates a certain way to provide the best consistency or group. Changing the barrel topology in any way will change this node. So while it might not reduce accuracy, it will seem that way until you do a new load work up. I think. I'm not an expert. But having briefly studied acoustical engineering, it makes sense.

At the very least, I would expect a POI shift.

[milotrain]

From what I understand 46&2 is correct. However there is a case where reducing the diameter of the muzzle too much will cause it the bore to expand at the muzzle and ruin accuracy. I wouldn't cut a 5/8-24 thread on a .30 cal barrel built for accuracy.

[DRM6000]

Thanks for the info guys.

Milotrain, I read about removing too much material and having the muzzle bell out. I was considering threading the muzzle to 5/8-24 on the .30 cal. bore. I'll play it safe and leave things as they are.

[MongooseV8]

You can cut a larger thread if you have a 1" bull barrel. I have a few 3/4x28 muzzles that shoot itty bitty groups. If done correctly there should be no noticeable change in accuracy potential. Poi shift and maybe a slight powder charge adjustment to compensate for new harmonics, at most are the only affects I have seen.

[DRM6000]

I know I can get the threads cut larger, but I have in mind a muzzle device that doesn't come in that size. Plus, many of the popular devices come in 5/8-28 so having other options is appealing.

[musketjon]

This, to me, sounds like a perfect case of '' If it ain't broke, don't try to fix it''.
Jon

[desert dog]

This, to me, sounds like a perfect case of '' If it ain't broke, don't try to fix it''.
Jon

Yep, if he is shooting tiny sub .25 MOA 5-shot groups regularly right now - leave the barrel alone! I would not change my load, shooting technique, cleaning schedule, bench rest, or ANYTHING on that gun at this point. I have rifles that I have dumped many thousands of dollars into to do that.

[Whatisthis?]

I've read that it won't affect "accuracy" per se. But adding weight, reducing weight, adding length, or reducing length to your barrel can affect how the barrel vibrates. The barrel is a giant tuning fork that vibrates at a specific frequency for a given load. And every object (not just a barrel) has a resonant frequency at which it vibrates and resonates with the most ease. The reason people do load work ups to find an accuracy node is to find that resonant peak at which the barrel vibrates a certain way to provide the best consistency or group. Changing the barrel topology in any way will change this node. So while it might not reduce accuracy, it will seem that way until you do a new load work up. I think. I'm not an expert. But having briefly studied acoustical engineering, it makes sense.

At the very least, I would expect a POI shift.

Correct me if I'm wrong because I haven't studied acoustical engineering, but wouldn't a resonant frequency with an object such as a barrel imply that the amplitude of the oscillation increases with that frequency, and therefore, is not what you want?

[FourT6and2]

Correct me if I'm wrong because I haven't studied acoustical engineering, but wouldn't a resonant frequency with an object such as a barrel imply that the amplitude of the oscillation increases with that frequency, and therefore, is not what you want?

Yes. That is what I was implying. I just didn't outright say it (and maybe the wrong word choice on my part). I'm guessing you'd want to find the load that makes the barrel vibrate in such a way as to give you the best groups. That doesn't necessarily mean you want to hit the barrels actual resonant frequency. Because as you imply, then the barrel would be whipping like crazy.

It's like noise-canceling headphones. You want the barrel to vibrate the least (I guess). So you want a load/charge that imparts a frequency into the barrel that cancels out that vibration. It's basically phase cancellation, no?

[jeremyro]

Yes. That is what I was implying. I just didn't outright say it (and maybe the wrong word choice on my part). I'm guessing you'd want to find the load that makes the barrel vibrate in such a way as to give you the best groups. That doesn't necessarily mean you want to hit the barrels actual resonant frequency. Because as you imply, then the barrel would be whipping like crazy.

It's like noise-canceling headphones. You want the barrel to vibrate the least (I guess). So you want a load/charge that imparts a frequency into the barrel that cancels out that vibration. It's basically phase cancellation, no?

Its not phase cancelation, its just finding the zero crossing point, like trying to make clean edits in protools. You just want the setup that makes the barrel's muzzle stay closest to zero. (Zero being the zero point on a sine wave graph or the original starting position of the barrel, not like on a scope) The rest of the barrel will move, there is nothing to be done about that, but ideally the muzzle is near a null point. If your muzzle is near the peak of a wave you will get the most chance of dispersion when shooting groups.

Adding a brake WILL change the resonance of the barrel, but it may or may not have a large impact on accuracy with your current load. You should be able to get back to the same performance if you work up a new load. Both of my long range rifles have brakes and they both shoot very well. I am not that into the idea of shooting a 338LM without a muzzle device.

[FourT6and2]

Its not phase cancelation, its just finding the zero crossing point, like trying to make clean edits in protools. You just want the setup that makes the barrel's muzzle stay closest to zero. (Zero being the zero point on a sine wave graph or the original starting position of the barrel, not like on a scope) The rest of the barrel will move, there is nothing to be done about that, but ideally the muzzle is near a null point. If your muzzle is near the peak of a wave you will get the most chance of dispersion when shooting groups.

Ok so then it's kinda like just shifting a sin wave left or right until the zero-crossing point lines up where you want it (at the muzzle)? I guess I thought it was about finding a load that creates an impulse that makes the barrel vibrate the least.

[jeremyro]

Ok so then it's kinda like just shifting a sin wave left or right until the zero-crossing point lines up where you want it (at the muzzle)? I guess I thought it was about finding a load that creates an impulse that makes the barrel vibrate the least.

Exactly right. Most loads create about the same impulse (amplitude) , you just get to move around the frequency (wavelength) of the waves.