Chucking a Proof barrel

[kck]

Going to chamber a Proof CF barrel for the first time and was wondering if anyone had anything they might do different as far as chucking it. It obviously has plenty of room on the shank end to hold with the standard aluminum shims but as far as holding for threading and crowning the muzzle is where I'm a bit concerned. I know that CF is pretty dang tough so thinking brass shims would be OK to not bugger it up as long as it's not too terribly tight? Any help would be greatly appreciated!

[Cajun Blake]

go directly to the source … call PROOF and ask their GS's opinion and recommendations

[kck]

Going to do that as well but I always like to ask around in case the seasoned guys have some different little tips or tricks. Updates to come and I'll try to do a video based on what I find out.

[catslayer]

go directly to the source … call PROOF and ask their GS's opinion and recommendations

THIS... or call Stick1 and see if what he has exsperienced

[txfireguy2003]

I'm certainly not "seasoned", working on my first barrel job now, and waiting for ATF to call me about the FFL. Here's my thought, tell me what you think:

I built a jig for truing actions based on Mike Bryant's design. It's basically a piece of steel tubing about 3" long with a 1.75" ID and thick walls with eight 1/2"-20 cap screws for adjustment..... basically two spiders on one short section of tubing. I then made an aluminum collet of sorts that fit inside that fixture with about 25-30 thou clearance, and an ID that fit the front action ring close, cut four slots about 3/4 of the way down the collet so it'll clamp on the action. Now I can load the action into the collet and the collet into the fixture and align it to run true using the 8 jacking bolts without bending or stressing the action.

Now, back to your question, what's stopping me from cutting a collet to fit the barrel and holding it the same way? I can promise you that setting the action up in that fixture to run dead true was WAY FASTER than setting up my barrel by holding the chamber end in the 4 jaw chuck and rne muzzle in the outboard spider...... not to mention I'm pretty sure the barrel is under stress between the chuck and spider. I know the muzzle is way farther off center than it should be. I'm going to remove it from the lathe and turn a collet to fit the barrel and try it again that way.

Below is a picture of my fixture and collet.

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[Stick1]

Going to chamber a Proof CF barrel for the first time and was wondering if anyone had anything they might do different as far as chucking it. It obviously has plenty of room on the shank end to hold with the standard aluminum shims but as far as holding for threading and crowning the muzzle is where I'm a bit concerned. I know that CF is pretty dang tough so thinking brass shims would be OK to not bugger it up as long as it's not too terribly tight? Any help would be greatly appreciated!

That carbon fiber is indeed tough.......but it will compress as it sits under stress. Meaning that your perfectly indicated bore likely won't be perfectly indicated if you come back and check it 30 minutes later. This will kind of address TxFireguys issue as well concerning his steel barrel indicating.

First, we know that not many bores will run true to the outside dimensions of the barrel once you get very far from either end. They will generally have some degree of hook or cork screw that can cause a problem when indicating on the bore itself, but holding the barrel in the chuck's perfectly flat jaws locked against the barrel's perfectly flat outer surface. If the bore was dead straight there would be no issue holding it in the outboard spider and directly in the chuck jaws, but they aren't dead straight. By setting up like this, you are basically bending the barrel to conform as you are indicating it. Not a good idea. The barrel needs to be able to pivot at 1 end to keep from bending, but still be held securely enough to be able to dial in and perform the work that needs to be done. There are several ways to accomplish this. The old tried and true (and most economical) way to do this is by holding the barrel in your chuck jaws with some sort of ring around the barrel.

Number 4 copper ground wire works really well for this. Preferably really weathered wire that came off an old power pole The stuff is hard as woodpecker lips and will take a lot more pressure than any of the newer copper wire you can find today. You'll likely need a small hammer to form it around the barrel if it's the good stuff. I have a pile of rings for just about every size barrel sitting on my bench from when we chambered on the manual lathes. One for the breach end, and another smaller one for the muzzle end when the barrel is swapped around to work on crowns/muzzle threads. We use simple 1/8" thick aluminum pads on the outboard spider side.

The issue with using the ring on the muzzle end of a carbon fiber barrel goes back to material compression. We made a series of 1.5" long aluminum "sleeves" with an internal taper to match all of the Proof and Hardy barrel profiles and a ring to fit over the sleeves. The sleeve distributes the stress of the ring over a larger area and allows it to be held very securely without compromising the barrel. Simple but effective. There are a million ways to skin this cat, but maybe this will give you some ideas to work with.

-Robert

[txfireguy2003]

That carbon fiber is indeed tough.......but it will compress as it sits under stress. Meaning that your perfectly indicated bore likely won't be perfectly indicated if you come back and check it 30 minutes later. This will kind of address TxFireguys issue as well concerning his steel barrel indicating.

First, we know that not many bores will run true to the outside dimensions of the barrel once you get very far from either end. They will generally have some degree of hook or cork screw that can cause a problem when indicating on the bore itself, but holding the barrel in the chuck's perfectly flat jaws locked against the barrel's perfectly flat outer surface. If the bore was dead straight there would be no issue holding it in the outboard spider and directly in the chuck jaws, but they aren't dead straight. By setting up like this, you are basically bending the barrel to conform as you are indicating it. Not a good idea. The barrel needs to be able to pivot at 1 end to keep from bending, but still be held securely enough to be able to dial in and perform the work that needs to be done. There are several ways to accomplish this. The old tried and true (and most economical) way to do this is by holding the barrel in your chuck jaws with some sort of ring around the barrel.

Number 4 copper ground wire works really well for this. Preferably really weathered wire that came off an old power pole The stuff is hard as woodpecker lips and will take a lot more pressure than any of the newer copper wire you can find today. You'll likely need a small hammer to form it around the barrel if it's the good stuff. I have a pile of rings for just about every size barrel sitting on my bench from when we chambered on the manual lathes. One for the breach end, and another smaller one for the muzzle end when the barrel is swapped around to work on crowns/muzzle threads. We use simple 1/8" thick aluminum pads on the outboard spider side.

The issue with using the ring on the muzzle end of a carbon fiber barrel goes back to material compression. We made a series of 1.5" long aluminum "sleeves" with an internal taper to match all of the Proof and Hardy barrel profiles and a ring to fit over the sleeves. The sleeve distributes the stress of the ring over a larger area and allows it to be held very securely without compromising the barrel. Simple but effective. There are a million ways to skin this cat, but maybe this will give you some ideas to work with.

-Robert

Yessir, I used the copper wire ring method around my barrel, and felt like it pivoted on the wire fairly well, adjustments seemed to be predictable etc. Then, I went to determine which side of the bore was "pointing up" so I could clock the barrel on the action with it pointing to 12 o'clock. That's when I noticed how far off center it was..... enough that my Inrerapid indicator won't read it, even on the outside of the barrel..... it's easily visible runout. I'm going to try my collet idea and see how it works, otherwise it's back ti the drawing board. The wire I used was actually 1/4" copper rod (round) and seemed hard, very hard to bend, but maybe it's soft enough that it's gripping the barrel still and causing the heavy sporter barrel to flex some. I may also try just releasing the tension on the spider and see if it changes my runout on the chamber end. If not, I'll just snug it back up without bending the barrel, but i'm afraid as soon as I let the tension off, it's going to move all around.

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[Stick1]

Yessir, I used the copper wire ring method around my barrel, and felt like it pivoted on the wire fairly well, adjustments seemed to be predictable etc. Then, I went to determine which side of the bore was "pointing up" so I could clock the barrel on the action with it pointing to 12 o'clock. That's when I noticed how far off center it was..... enough that my Inrerapid indicator won't read it, even on the outside of the barrel..... it's easily visible runout. I'm going to try my collet idea and see how it works, otherwise it's back ti the drawing board. The wire I used was actually 1/4" copper rod (round) and seemed hard, very hard to bend, but maybe it's soft enough that it's gripping the barrel still and causing the heavy sporter barrel to flex some. I may also try just releasing the tension on the spider and see if it changes my runout on the chamber end. If not, I'll just snug it back up without bending the barrel, but i'm afraid as soon as I let the tension off, it's going to move all around.

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"Then, I went to determine which side of the bore was "pointing up" so I could clock the barrel on the action with it pointing to 12 o'clock. That's when I noticed how far off center it was..... enough that my Inrerapid indicator won't read it, even on the outside of the barrel..... it's easily visible runout."

If you are trying to use the "clock the barrel" approach, you are almost always going to see that kind of runout by default. Since the method hinges on indicating over an entire section of the bore instead of a single point in the bore running parallel with your set up. Basically you have a straight barrel with crooked bore in most cases, so anything you do to get the crooked bore running "straight" will just manifest itself as runout on the outside of the barrel. Most guys using this approach will ignore what the other end of the barrel is doing at this point as it will be dealt with in the same manner when it's flipped to work the other end. They will simply mark the "high spot" and do the clocking as a separate step at the end of the process, after the barrel has been test fitted to the receiver under actual torque values to determine where the high spot will land. I get the theory to the method - the bullet enters a "straight" section of the bore and leaves a "straight" section of the bore. I have used it with good results many times, but I'll never do one like that again. I find it an overly complicated method that has several potential pitfalls, and provides no advantage over a couple of other methods that produce much more consistent results. With any method using an outboard spider, you will need that pivot point to minimize bending forces being applied to the barrel to some degree.

[txfireguy2003]

"Then, I went to determine which side of the bore was "pointing up" so I could clock the barrel on the action with it pointing to 12 o'clock. That's when I noticed how far off center it was..... enough that my Inrerapid indicator won't read it, even on the outside of the barrel..... it's easily visible runout."

If you are trying to use the "clock the barrel" approach, you are almost always going to see that kind of runout by default. Since the method hinges on indicating over an entire section of the bore instead of a single point in the bore running parallel with your set up. Basically you have a straight barrel with crooked bore in most cases, so anything you do to get the crooked bore running "straight" will just manifest itself as runout on the outside of the barrel. Most guys using this approach will ignore what the other end of the barrel is doing at this point as it will be dealt with in the same manner when it's flipped to work the other end. They will simply mark the "high spot" and do the clocking as a separate step at the end of the process, after the barrel has been test fitted to the receiver under actual torque values to determine where the high spot will land. I get the theory to the method - the bullet enters a "straight" section of the bore and leaves a "straight" section of the bore. I have used it with good results many times, but I'll never do one like that again. I find it an overly complicated method that has several potential pitfalls, and provides no advantage over a couple of other methods that produce much more consistent results. With any method using an outboard spider, you will need that pivot point to minimize bending forces being applied to the barrel to some degree.

Sorry to have hijacked your thread OP.

So, basically, I got my chamber end running true by measuring runout with the long contact indicator as far in as it would reach, and right at the edge of the bore. I adjusted the 4 jaw chuck, clamping against a copper ring running around the barrel shank, af well as the outboard spider bolts on the muzzle, until the chamber was running true. Measuring on top of the lands, I'm running as true as my eye can see on the Interapid .0005" indicator, over a span of 2.75". Checked numerous places in between. I then cut off about 1/2" of barrel to make the taper fit my stock channel a bit better, threaded and cut a counter bore, then measured runout again with no change (except now i can reach further into the barrel) still no runout that I can measure. During all that, I completely ignored the muzzle end after I got the chamber end running true.

My plan was to figure out how the barrel needed to be indexed, although I don't know why, since I'm going to cut 4-5" off when done, the bore might not be pointing the same way in that section as it is at the end of the full length blank. My thinking though, is that I needed to do it now, since the only way I know to clock the barrel is by removing material from the barrel shoulder, so that needs to be done before chambering. The more I think about it though, how do the guys that run prefits clock their barrels? They don't worry about it, they set headspace and lock down the barrel nut. I may take that approach and go ahead and chamber with the current setup, then flip it around and indicate on the muzzle end and cut it off, cut my crown and go shoot.

I still want to try my collet idea, but I'll do it on a take off barrel first. My basic idea is that it keeps all the stresses and what not over a shorter, thicker and stiffer section of barrel, reducing the chances of bending to nearly zero. I'm fairlycertain I'm seeing bending now, even with the wire pivot ring. I'd love to buy one of the Truebore Alignment chucks, but I think I'd be better served by spending my money on practice stock at this point. That dude is proud of that chuck...... my collet idea sort of acts the same way though, you clamp onto a section of barrel maybe 2-3 inches long, then adjust the clamp around until you're running true, and let the other end "float" out there wherever it needs to be so the chamber section is running true when the reamer goes in. Basically, it would take the pivot ring out of the equation and replace it with a 3" long sleeve cut to fit the barrel taper. Then, since I'm using 1/2" bolts on both ends of that sleeve, I can pivot the whole assembly around as needed. Am I way off base, or even making sense?

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[Stick1]

That probably explains why you were seeing so much runout if you were trying to measure the bore from the throat area all the way back to the end of the barrel and get it all running true. Everything from the throat back doesn't really matter. What does matter is where your bullet will actually make contact with the bore. Indicate on that point. Your chamber will clean everything up from there back, and it will all be running concentric to your bore where the bullet actually sits. I would also recommend taking your readings off the grooves rather than the lands, especially on 5R barrels.

[txfireguy2003]

That probably explains why you were seeing so much runout if you were trying to measure the bore from the throat area all the way back to the end of the barrel and get it all running true. Everything from the throat back doesn't really matter. What does matter is where your bullet will actually make contact with the bore. Indicate on that point. Your chamber will clean everything up from there back, and it will all be running concentric to your bore where the bullet actually sits. I would also recommend taking your readings off the grooves rather than the lands, especially on 5R barrels.

Okay, I see how measuring where the throat will end up will make the chamber concentric at that point, but it won't be aligned axially necessarily. Are you then going to the muzzle end and aligning it there, or just getting it concentric at the one spot? I feel like measuring at the two points gives the same axial alignment that running a bushing on a tapered indicating rod into the bore and measuring runout on the rod in two spots would.

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[kck]

The issue with using the ring on the muzzle end of a carbon fiber barrel goes back to material compression. We made a series of 1.5" long aluminum "sleeves" with an internal taper to match all of the Proof and Hardy barrel profiles and a ring to fit over the sleeves. The sleeve distributes the stress of the ring over a larger area and allows it to be held very securely without compromising the barrel. Simple but effective. There are a million ways to skin this cat, but maybe this will give you some ideas to work with.


Gotcha. Yessir, this is kinda what I was looking for as I also felt that it would be best to distribute the pressure over a greater area when trying to hold the muzzle end. Great input and much appreciated. May make an aluminum slotted sleeve with internal taper to match the contour of the muzzle similar (I think) to what you did. I'll try to update as I go as well.

[HDWRENCH]

Not a gun smith but machine engine parts we have to hold +/- .0001 on avg over a large bore and it has to straight and round once final hone..

So with that in mind am I reading this right.. Check OD with TIR of barrel and you find that the bore is not centered ?? ?? I mean we see it all the time , but for us its not a factor cylinder can move some and piston can slide on wrist pin .

[txfireguy2003]

Not a gun smith but machine engine parts we have to hold +/- .0001 on avg over a large bore and it has to straight and round once final hone..

So with that in mind am I reading this right.. Check OD with TIR of barrel and you find that the bore is not centered ?? ?? I mean we see it all the time , but for us its not a factor cylinder can move some and piston can slide on wrist pin .

That's correct, sort of. The barrel bore isn't necessarily centered, and never dead straight. It may be centered in one spot on one end, then 1/2 way down the tube, it may be several thousandths off center. The issue is not in placing the hole to start, it's that it's impossible to drill a perfectly straight hole that's 50-60 times the diameter. The bit wanders, but you know that. So for that reason, gunsmith's indicate to the ID, not the OD. There's are several methods of taking that measurement, and that's what Stick1and i are discussing. I've seen where some guys get it running concentric at the chamber end and the muzzle end and ignore what's in the middle. I've seen some that use an indicating rod riding on the bore and hanging out the chamber end and the measure tir on the rod. I've also seen a method that uses a bushing on a rod ands ther rod is held in the trailstock. The bushing is run into the bore a certain distance and the TIR is measured right where the rod enters the bore, then it's repeated in several spots throughout the chamber area of the barrel..... this one makes the least sense to me, but I understand it gets good results for those who use it.

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[kck]

Heard back from DJ at Proof a bit ago. He said that brass shims in a 4 jaw should be just fine as long as I don't crank the hell out of if. Should be able to update through the next week.