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bubbas4570

Thinning a barrel

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 I have a I have a question for you guys, I'm going to take my 16 in heavy barrel and my APF 308 AR and send it into APF to have it machined down to a pencil profile. My question is what do you think I'm going to actually lose in weight taking off that much metal off of that Barrel?

Before I get a bunch of comments about just go buy a different Barrel, I cannot find a 16 inch barrel with the rifle length gas system in a pencil profile. I couldn't  find a medium weight with a rifle length, maybe my gun Foo or search skills really suck. Either way I've not been able to find something that comes in the 16 in length with the rifle length gas system.

And part of this is what we were talking for the cost if machining my barrel down...... I can't replace a barrel for that cost.

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7 minutes ago, bubbas4570 said:

Before I get a bunch of comments about just go buy a different Barrel, I cannot find a 16 inch barrel with the rifle length gas system in a pencil profile.

X-Caliber can make that for you, depending on what dimensions you are associating to pencil profile. I got my 16 inch rifle gas from them several years back. Hopefully they have learned a bit about port sizing by now, mine came seriously under gassed but it was an easy fix. They get about $300, plus $120 if you want fluting.

http://x-caliber.net.revlis.arvixevps.com/ar-10

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 I'm having my currently owned the barrel milled down, so I don't need anyone to Make me one. This Barrel shoots good, it works without fail, so I already know that much of it is correct.

 

What I was looking for is personally how much weight do you think I'm going to drop off of this Barrel?

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3 hours ago, bubbas4570 said:

 I have a I have a question for you guys, I'm going to take my 16 in heavy barrel and my APF 308 AR and send it into APF to have it machined down to a pencil profile. My question is what do you think I'm going to actually lose in weight taking off that much metal off of that Barrel?

Before I get a bunch of comments about just go buy a different Barrel, I cannot find a 16 inch barrel with the rifle length gas system in a pencil profile. I couldn't  find a medium weight with a rifle length, maybe my gun Foo or search skills really suck. Either way I've not been able to find something that comes in the 16 in length with the rifle length gas system.

And part of this is what we were talking for the cost if machining my barrel down...... I can't replace a barrel for that cost.

The only way you will know how much weight is lost from milling is to weigh it now and then after milling, it is hard to calculate weight without knowing some critical dimensions and the mass density of the steel. So, just mill away!

1 hour ago, bubbas4570 said:

 I'm having my currently owned the barrel milled down, so I don't need anyone to Make me one. This Barrel shoots good, it works without fail, so I already know that much of it is correct.

 

What I was looking for is personally how much weight do you think I'm going to drop off of this Barrel?

 

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I had a feeling there were no quick and easy answers. There usually isn't for questions that come from my mind.....

 

I was going to look up some of Faxons' specs just to see a proximal amount....and thank you.

 

And I am not going after ounces, just some good weight loss.....wish it were that easy for my body....."just mill a lot off there!"😆

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I had a 16" heavy rifle length 556 barrel milled down  from .925 to .625 between the fsp and extension.  It cut the weight in half. 

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You could do the math. Solve for volume before and after.  The weight will be the same ratio. 

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I wonder about the barrel maintaining accuracy after taking that much off of it. It's been said that removing material can have an effect on the internal stresses of a barrel. I have no idea if that's true or not.

My DPMS LR308 has a heavy barrel on it and it was a straight cut at the muzzle, no threads. It's diameter behind the gas block is 1" and it WAS .930 in front of the muzzle. I had a machinist friend of mine cut it down to .750 in front of the gas block and thread the muzzle 5/8-24. I couldn't see any deterioration in the accuracy afterwards but I'm not a good enough rifleman to wring a lot of accuracy from a rifle to start with.

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4 minutes ago, 392heminut said:

I wonder about the barrel maintaining accuracy after taking that much off of it. It's been said that removing material can have an effect on the internal stresses of a barrel. I have no idea if that's true or not.

Yep, it's gonna change the harmonics of that barrel, and exactly why you stated - stress relief.  Stress relief is an important aspect of barrel manufacturing, and when it occurs in the machining process.  You can't just cut a barrel down like that, and do nothing else.  At a minimum, your zero will change. At the maximum, the accuracy of that barrel goes to shiit.

I'd love to hear from @308kiwi on this, because I know he's a barrel-machining Ninja. 

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On 6/2/2019 at 11:53 AM, 98Z5V said:

Yep, it's gonna change the harmonics of that barrel, and exactly why you stated - stress relief.  Stress relief is an important aspect of barrel manufacturing, and when it occurs in the machining process.  You can't just cut a barrel down like that, and do nothing else.  At a minimum, your zero will change. At the maximum, the accuracy of that barrel goes to shiit.

I'd love to hear from @308kiwi on this, because I know he's a barrel-machining Ninja. 

Yep, will definitely change the harmonics of the barrel, more than likely in a negative way.

Depending on who and how the barrel is machined could well even destroy it, in accuracy terms.

At the very least if I was to re-profile a barrel I would use a travelling steady on the lathe carriage directly opposite the cutting tool to minimise deflection and tool chatter of the barrel as the tool moves along its length, the same can be said for fluting barrels, the tool load required to remove the material, whether fluting or profile turning, will deflect/flex the barrel as the tool moves along, the question is...is the barrel going to return to it's original 'true'? And what other extra stresses is the turning inducing into the barrel, stresses that you cannot relieve after the fact.

The thinner profile you go the worse these issues become.

Purpose built barrel profiling machines, (lathes), turn the profile from at least two cutting points, opposite each other and the tools open or close, depending on which direction the barrel is being turned to create the taper, in the case of a parallel barrel the tools simply remain at one point in relation to their travel.

When turning a parallel barrel I used a travelling steady, If I have a job come in that requires taper turning, and we are talking barrel length tapers here, I outsource it to a friend that has a CNC lathe that also runs a steady but the steady is advanced with the taper by the lathe controller.

IMO, don't do it unless the person doing the work for you is aware of what they are doing.

 

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Timely discussion, I just picked this up from my mate after he profiled it for me from a parallel blank, he did the work in a freakin expensive and very flash CNC lathe that his machine shop just installed this year, does a beautiful job.

This was profiled from a 1:8 twist 24" .224 stainless blank that's destined for a 220 Swift bolt rifle build I'm working on.

 

220 Swift barrel.jpg

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That's a great looking profile!...  Tell that guy...     :hail:

I saw in the news today that a total of 530 guns have been turned in so far.  Keep up the fight, brother.   :thumbup:

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47 minutes ago, 98Z5V said:

That's a great looking profile!...  Tell that guy...     :hail:

I saw in the news today that a total of 530 guns have been turned in so far.  Keep up the fight, brother.   :thumbup:

Will do, 1.250" at the chamber end, .875" at the muzzle, it's going to be a heavy monster😎 

Yeah, 530 guns 'handed in', we are betting that the 530 that have been 'handed in' are just a few personal rifles of police officers, they had no choice, hand them in and set an example or your career is over, this is the sort of crap and corruption that is going on, as far as I am aware none or at the very least only a small handful of civi rifles have been handed in. And rough estimates are that there are in excess of 75,000 AR15's in NZ, let alone all the other semi auto's of which there could be 250,000+.

I remember back in the 80's and 90's the 20ft containers of Norinco SKK's, SKS's and 56S's that arrived in NZ, these guns are still out there, they don't just go out of circulation. So 530 doesn't even figure as a statistic as far as the volume that potentially are still out in circulation, our Govt just don't have a freakin clue. Idiots.

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We have to fight "feelings" - and "feelings" is what is driving all this mess, everywhere, here too  Our dipshiit politicians keep trying to prey on feelings, and use images, stories, and complete made-up bullshiit that doesn't even matter-just trying to get those "feelings" to enact another law-on-top-of-laws that we have here.  Like that would make a single difference, when they already have a law for everything.  Then another one, and.... 

I feel bad for you, brother, because everything that was just enacted in your country was "feelings."  You already had laws in place, and they preyed on "feelings" of idiots that don't know any better. As gun owners vs/ populace, you are outnumbered over there.  Here in the US, gun owners outnumber the populace - but that doesn't matter.  Not when they're trying to play the feelings of the weak.  We're as fukced as you're been, it's just a matter of time, before they can get the feelings on their side and vote some shiit through. 

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"We're as fukced as you're been, it's just a matter of time, before they can get the feelings on their side and vote some shiit through."

 

Unfortunately this is a very accurate statement.

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Sad thing is, the last count showed that only 22% of the Population of the US owned the 400 million firearms in this country. That means there is only 77 million people owne them. There is far greater numbers now that want to take them away. I am not sure how real the new on Fox has been of late, but they just said that 56% of the American people want a assault weapons ban. I say bullpoopy, but not sure what to really believe anymore from the media. Also back in the 70's there where 42% of the population that owned firearms. So what changed, well more laws, more gun free zones & more liberal brainwashing in our schools in the last 3-4 decades since then. I do find it awesome that Texas did add pro gun laws to their books allowing more people to carry in areas that where gun free zones, only unless the place of buisness allows it. 

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On 6/1/2019 at 4:53 PM, 98Z5V said:

Yep, it's gonna change the harmonics of that barrel, and exactly why you stated - stress relief.  Stress relief is an important aspect of barrel manufacturing, and when it occurs in the machining process.  You can't just cut a barrel down like that, and do nothing else.  At a minimum, your zero will change. At the maximum, the accuracy of that barrel goes to shiit.

I'd love to hear from @308kiwi on this, because I know he's a barrel-machining Ninja. 

Lance is the guy for this !!!

I don't think it's worth the effort, " if It ain't broke don't fix it !". Buy another barrel just like you want it and build another gun. I have actually done this on a couple customer's guns and it turns out nice but the weight loss of a pound is probably not the best use of money.

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MikedaddyH, my initial problem was that I couldn't find ankther barrel like i wanted.....medium to thin profile, 16" length, and rifle gas length......very rare animal indeed. Add to that, I am a very cheap screw, and I/we had a problem.

 

My solution.......sell the rifle and get something else. Problem solved.

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