Gunsmithing Some barreling work.

[LRI]

I like sharing this kind of stuff as it seems to generate interest and lots of commentary/discussion. In the interest of keeping things interesting around here I thought I'd share how I plumb a barrel on a receiver.

1. Paperwork.

Documentation is a big deal for me. I build every rifle from a sheet that I've conjured up to record all the critical dimensions. This is nothing more than getting some numbers to work with off the action. I verify the thread pitch, measure the height from the receiver face to the bolt, barrel serial number, caliber, twist, the cartridge, etc.

Now its onto setting the barrel up in the turning center. This is the machine I use for all my barrel work. A Doosan Mecatec 10 tool slant bed CNC turning center. I've modified the machine a bit to work for barreling up actions. It's been equipped it with a Dunham 16C collet spindle nose that's able to be indicated just like a four jaw chuck. I like the idea of collets because it offers much more rigidity which means the potential for improved surface finishes. This is the "baby" of the shop.

Time to indicate the barrel and get to work! First we have to set up a special tool I made for doing this. Indicating a barrel is nothing more than getting the hole that the bullet travels down to rotate on the same imaginary center that the spindle of the machine rotates on. We want them to be <span style="font-style: italic">concentric</span> with one another. I do this a little differently. Since all barrels are "bent" to some degree I decided I wanted to be able to pick the place where I make the bore concentric with the machine. I figure where the bullet is going to be introduced to the lands is the best place. So I built a tool that allows me to do this. It has different adapters for each caliber and pivots on a gimbled base that fits in my reamer holder. Here's the tool being set up for this particular caliber. My method for determining how far to stick this up the barrel is pretty "scientific". I lay the reamer next to it and mark the shaft with a black marker. It's a visual "guess" where the freebore transitions to the throat. Paring them up I mark the stylus where the scribe mark is on the reamer. Then we cram the contraption up the bore like a rectal thermometer.

Here's the tool installed in my reamer holder in preparation of truing things up. The plumb weight is just to ensure the tool follows the bottom of the bore. Nothing here actually rotates, it just bobs up and down as the barrel flops around. Once the bore is concentric it'll quit moving.

Now I dial back the hydraulic pressure being exerted on the chuck so that I can move things around without stripping the heads of the allen set screws.

Barrel is all trued up now after some fiddling with the set screws and careful use of a craftsman deadblow mallet. A few taps makes pretty quick work of all this.

This particular action is new for me so it requires I write a new program for the lathe. I start with a simple CAD model of the tennon that I use to write a program with. This is where the "cheat sheet" comes in handy as all my dimensions are recorded. I write all my lathe code longhand so the model is just a convenient visual to pull dimensions from. With actions that I've used before I apply the same numbers from my "cheat sheet" and just edit values in a master program for that particular brand/type of receiver. Much easier/quicker that way.

Once done I'll load the program into the machine's control via the RS232 cable.

 

[LRI]

Re: Some barreling work.

Now it's matter of setting the chuck pressure, the tool work offset, and letting the program do it's thing. I start by contouring the tennon and qualifying the diameter with my 1"-2" Mitutoyo Mic.

Threading to fit the action starts with a generic G92 threading cycle. It gets the thread "close". Close means the bulk of the material is out of the way but not so much as to allow the action to actually thread on. From here it just cycle through additional thread cycles written to only take .001" at a time. Once I get to where the action will go onto the barrel just enough to not stick a thread I skip through the rest of the passes and move onto boring the breech/chamber to get it concentric for the reamer.

(I forgot to take this photo for the actual barrel I'm working on so I'm substituting this one just to illustrate.)

Barrel is now threaded for the action and its time (yet again) to do some inspection. I like to set breech clearances at .015" as it gives enough room for funk without running the risk of rupturing cases and what not. Since the web is still well inside the bore and fully supported I'm not too concerned about a case "sneezing" due to lack of support from the chamber. I like to keep inspection as simple and dumb as I can as they seem to work the best. In this case I leave the fancy math to the school teachers and stick a piece of soft lead solder to the lug face of the bolt. I'll hold it with a dab of grease. From there I'll just insert it in the action and rotate into battery. The camming action squishes the solder and when removed provides a no question dimension. I measure with a pair of calipers and record it. Easy stuff. . .

In this case I was off a bit. My clearance is only .003". No worries as I'll just edit the code and reface the tennon an additional .012" to get the .015" I'm looking for.

Now I'm ready to chamber. My reamer holder never changes position. It stays in the machine and I've checked it enough times to know that it repeats. (It better for what the machine cost). One thing I did forget to mention is the spindle of this machine. When starting one of these jobs on a cold machine I'll let the spindle run in at 1000 rpm for about 15 minutes. The casting that the bearing cassettes run in warm up and pick up about .003" from ice cold. This is an important step for the chambering part since we are using a tool that depends on a reliable center position. If the tools used in turning/threading are above/below the part a bit its not nearly so critical since that can be compensated for with some easy edits in the tool wear offset page. Machine is all warmed up by the time the chambering part comes.

I start by selecting the right pilot size. (I own every pilot size Pacific Tool makes from 17 to 338 caliber) From there it's a matter of establishing a start point, setting the RPM of the spindle, and then hosing the tool down with the home brew cutting fluid I use. A 50/50 mix of Castol Moly D tapping fluid and Marvel Mystery oil. Our chamber today is a 6mm 22-250 Remington Ackley Improved with a .274"ND and .098"FB. Easy stuff...

 

[LRI]

Re: Some barreling work.

Chamber is now cut to depth. Again the dumb/simple process is what I resort to. When I get close to my depth I'll pull the tool out of the way, screw the action onto the barrel partially and then drop the bolt on the GO gauge. I'll then screw the action on until the gauge hits the chamber/bolt face. Then just measure the gap between the receiver/shoulder and add that to my last depth. I do however have to compensate a couple thousandths for crush when the barrel gets pulled up tight on the action. I torque all my 1.0625" OD tennons to 125lbs. That nets about .002-.0025 of crush. I'll add an additional .0035" to my final reamer depth which should give me a "GO+.001" chamber depth once I'm all done. It's very, very rare that I have any issues with chamber surface finish so I just use some 320 emery and green scotchbrite to buff the chamber up when I'm done. This ensures I'm not altering the internal dimensions or rolling corners in the shoulder/case body/neck area. The other part of this to pay attention to is surface finish. I personally don't advocate a chamber polished to a mirror finish. they look pretty and guys get all hot/bothered by it, but in my experience its actually hurting things (brass) a little bit. Reason is the flow of material. Brass wants to typically move towards the neck/shoulder over a period of time. The resizing process does it and so does firing. I like to have a sort of cross hatch pattern typical of an engine's cylinder so that the little scratches "bite" the brass and hold it. It's a fine line though as going too coarse means that the brass ends up looking frosty after being fired. I also use a shot of Kroil or WD40 as it keeps the chips/abrasive in suspension and helps prevent it from loading up in the chamber. 1K RPM and some quick strokes back and forth.

Once it's all done it looks like these:

6mm 22-250 Remington Ackley Improved:

300 Remington Ultra Magnum:

Now we move onto the inspection process. Are things the way I want them?

 

[LRI]

Re: Some barreling work.

Inspection is a process of checking the total indicated runout (TIR) of the chamber and the barrel tennon. I check the chamber in two locations. Up by the shoulder/body junction and back at the web just in front of the breech. I check the tennon at behind the shoulder where there's no threads. (recoil lug sits here)

I use a Brown and Sharp "best test" indicator with a .00005" resolution.

Lets see how this one came out.

Case web area looks to be .00005" TIR. (I can live with that)

Close up view:

Now onto the body/shoulder junction:

Zeroing the indicator since it moved due to the taper in the case:

Here's our number, .00015". Most chambers are considered "good" if TIR is held to within .001". In this case its about 6 1/2 times inside of that dimension.

Now the tennon. .00015" again is the number.

With everything checked and completed now its onto flipping her around and getting the crown tuned up.

 

[JSTARSZ]

Re: Some barreling work.

For us novices that is a great tutorial on the process. I have read books so I have a clue but you really explained the process for my level of understanding - thanks for taking the time and great pics by the way.

 

[LRI]

Re: Some barreling work.

I basically use two different crown styles. A true 11* target crown and a recessed 11* crown. Application drives what gets used. In this case my customer is an Avid BR shooter who likes to use cartridges that aren't "mainstream". I'll be cutting an 11* target crown for this barrel.

Set up is essentially identical to chambering only now I'll just use the indicator to fine tune. no need for the tool since I know where the bullet is going to be when it exits the barrel. I'll chop the barrel to length with a parting tool, use a chamfering cutter held in my hand to nick the burrs off and then go about getting the bore centered up.

From there its touch the tool work offset again, load the right program, and let her rip.

Now that were essentially done all that's left is polishing up the barrel and stickin her into the CNC mill to engrave the caliber and the shop name.

.

Finished!

Here's a sample photo from an older job. I run my engraving in batches of 4-5 so our little 6mm guy will get shelved till I get a few more done.

Thanks for looking. Enjoy your Memorial Day gents.


Chad

 

[SDWhirlwind]

Re: Some barreling work.

Nice write up Chad. Thank God I am a shadetree metal butcher. I damn sure don't have the knowledge and machines for that much detail and would probably be tooo lazy to put that much work into it if I did just to kill a coyote or p dog. At least with your experience and tooling you give your customers what they pay for. The shooting community should be thankfull for the anal perfectionists

that troll this site and share their ideas and techniques. Thanks for the time and pics.

Have a super Memorial Day yourself.

Respectfully,
Dennis

 

[JimT]

Re: Some barreling work.

The cabinet for the reamers is SWEET. I would love to acquire something like that. An organized shop is a more efficient shop.

 

[Bacarrat]

Re: Some barreling work.

I love threads like these where craftsmen show how they do what they do.

Never knew they made dial indicators that can go in the hundred thousandths.

 

[coldboremiracle]

Re: Some barreling work.

Some times I wonder if I have enough time left in life to catch up to some of you guys! Beautiful work!

 

[LRI]

Re: Some barreling work.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bacarrat</div><div class="ubbcode-body">I love threads like these where craftsmen show how they do what they do.

Never knew they made dial indicators that can go in the hundred thousandths. </div></div>

Brown and Sharp Best Test Model 7033-5

 

[nashlaw]

Re: Some barreling work.

Thank you, Sir! That was an education. I appreciate you guys that build precision rifles for a living taking the time away from production to share with us. Great looking work.

David

 

[Cinch]

Re: Some barreling work.

That's some pretty interesting stuff, Chad. You're a true craftsman. Thanks for posting this.

 

[bigwheeler]

Re: Some barreling work.

Thanks also. It's a pleasure to see guys willing to go for the best they can do.
You are a true craftsman.

 

[usmcMT]

Re: Some barreling work.

Brother Dixon, great writeup.

 

[dinc]

Re: Some barreling work.

Beautiful. The finish on the tennon alone makes me want to send some work. Thanks for sharing.

 

[Bryan27]

Re: Some barreling work.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">
Time to indicate the barrel and get to work! First we have to set up a special tool I made for doing this. Indicating a barrel is nothing more than getting the hole that the bullet travels down to rotate on the same imaginary center that the spindle of the machine rotates on. We want them to be <span style="font-style: italic">concentric</span> with one another. I do this a little differently. Since all barrels are "bent" to some degree I decided I wanted to be able to pick the place where I make the bore concentric with the machine. I figure where the bullet is going to be introduced to the lands is the best place. So I built a tool that allows me to do this. It has different adapters for each caliber and pivots on a gimbled base that fits in my reamer holder. Here's the tool being set up for this particular caliber. My method for determining how far to stick this up the barrel is pretty "scientific". I lay the reamer next to it and mark the shaft with a black marker. It's a visual "guess" where the freebore transitions to the throat. Paring them up I mark the stylus where the scribe mark is on the reamer. Then we cram the contraption up the bore like a rectal thermometer.

Here's the tool installed in my reamer holder in preparation of truing things up. The plumb weight is just to ensure the tool follows the bottom of the bore. Nothing here actually rotates, it just bobs up and down as the barrel flops around. Once the bore is concentric it'll quit moving.
</div></div>

When you dial in the bore, are you running a bushing up to the point where the bullet will eventually meet the rifling to accomplish this?

When you say that nothing actually rotates, does that include the barrel or are you speaking only of the measuring set up? I'm not following you on the plumb bob and everything just bobbing up and down rather than rotating. Would you mind expanding on this part?

 

[Jeff808]

Re: Some barreling work.

Awesome write up!! One of these days I would like to learn how to build precision rifles, just don't have the time right now. By the way, what's the cost of that specific CNC you got there?

 

[Furtaker_.223]

Re: Some barreling work.

Kinda makes me sick to my stomach that I didn't go farther in school............


Awsume work

What is it going to cost me to have my rifle re barreled?

 

[jwSubMOA]

Re: Some barreling work.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan27</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">
Time to indicate the barrel and get to work! First we have to set up a special tool I made for doing this. Indicating a barrel is nothing more than getting the hole that the bullet travels down to rotate on the same imaginary center that the spindle of the machine rotates on. We want them to be <span style="font-style: italic">concentric</span> with one another. I do this a little differently. Since all barrels are "bent" to some degree I decided I wanted to be able to pick the place where I make the bore concentric with the machine. I figure where the bullet is going to be introduced to the lands is the best place. So I built a tool that allows me to do this. It has different adapters for each caliber and pivots on a gimbled base that fits in my reamer holder. Here's the tool being set up for this particular caliber. My method for determining how far to stick this up the barrel is pretty "scientific". I lay the reamer next to it and mark the shaft with a black marker. It's a visual "guess" where the freebore transitions to the throat. Paring them up I mark the stylus where the scribe mark is on the reamer. Then we cram the contraption up the bore like a rectal thermometer.

Here's the tool installed in my reamer holder in preparation of truing things up. The plumb weight is just to ensure the tool follows the bottom of the bore. Nothing here actually rotates, it just bobs up and down as the barrel flops around. Once the bore is concentric it'll quit moving.
</div></div>

When you dial in the bore, are you running a bushing up to the point where the bullet will eventually meet the rifling to accomplish this?

When you say that nothing actually rotates, does that include the barrel or are you speaking only of the measuring set up? I'm not following you on the plumb bob and everything just bobbing up and down rather than rotating. Would you mind expanding on this part?


He's refining an old school machining trick.The probe and indicator is stationary while he manually turns the chuck and indicates using the four screws on his collet chuck to move the barrel around.Once the indicator shows the minimum runout of the probe he is dead nuts.The plumb bob just keeps the probe against the point on the bore ID he wants to indicate,hope that made sense.

</div></div>

 

[SavageStag]

Re: Some barreling work.

Awesome write up, thanks for taking the time to share with us.

 

[LRI]

Re: Some barreling work.

I'll attempt to shotgun the answers to questions.

Yes, the "old school" machining trick explanation is spot on.

School? What's a school? I barely graduated H/S and lasted a month in college before dropping out/quitting. The vast majority of all this is self taught. I do have friends/colleagues that help me from time to time when I get stuck, but by and large its me, a manual, and a piece of scrap material sorting stuff out. It can be done with persistence/stubbornness!

A lathe like that one run in the 60K range in terms of cost. Then figure another 5-10K to get it here, 3K to set it up, and another 10K+ to tool it up. I don't like talking about it. It just brings on the buyer's remorse and nausea feeling. . .

This one is a 2006 model. Its a demo that a dealer had set up.


Thanks guys.

Chad

 

[Bryan27]

Re: Some barreling work.

Makes sense to me now. The point of the probe rides the bottom of the bore, as you turn the chuck, the probe rises at the high points and falls at the low points until it is adjusted to zero. But with a piloted reemer and a floating reamer holder, is this going to make a difference? It seems to me that it may be better to dial in the barrel at two points, the point the bullet meets the rifling and the point the reamer enters the bore, having them both running in the same plain if the barrel isn't perfectly straight. If only indicated at one point, 3" deep into the bore, wouldn't it be possible that the bore is runnig out of concentricity where the reamer begins to cut? By the time the pilot reaches full depth, wouldn't it taper wider toward the breech end of the cut?

Sorry to be hijacking the thread, I have a tendancy to think out loud. I'm just trying to learn all I can about this stuff, not argueing or doubting it one bit.

 

[LRI]

Re: Some barreling work.

That'd be why I single point bore the hole behind the bullet's engagement point to the breech face. Since we know we are reaming a banana the center point changes an arbitrary amount at any given linear position. The reamer will do its best to follow whatever hole its shoved into. If the boring operation is done correctly the reamer will naturally want to run concentric to that hole as it feeds into the material- to the point that a pilot up front really isn't even needed. I've tested and proven that one as well. When I get to the new building and have the room for my "psychomatic" high pressure/high volume coolant pump I plan to run my reamers pilot free so that I have more fluid delivery through the nose of the tool.

All I'm wanting to do is keep the bearing surface of the bullet as tangent to the bore as I can. Assuming the loaded ammunition is reasonably good the rest should follow along accordingly.

Thus far I've seen no reason to change the process. Everything is coming out pretty dern good. Guns shoot very well, they still run fine (feeding/extraction) and customers are very pleased. All pointing in the right direction.

 

[border_reiver]

Re: Some barreling work.

Chad,

Nice work, good to see we have a class act goin on back home in SoDak..

Are you using PTG 3 flute roughers, or straight to finish reamer? Are you pecking the chamber to finishh headspace or is it a straight shot to a dimension, then measure and finish? Also, is the a flush thru barrel set up? haha, all good stuff. later man

 

[LRI]

Re: Some barreling work.

I don't use a rougher. I feed the reamer by hand. I used to try and keep depths on record and write peck cycles but it bit me once or twice so now I just feed by hand in .0001" increments. I'll plunge about 3-4 hundred at a time, rapid out, blow it off, and then go back for more. I don't have a pressurized set up yet. I've got the pump (it's a monster!) and the filter enclosures made, but no room for the thing in this shop. My new shop will be able to facilitate it so I'm saving it for there. I still have another CNC mill, a monster of a Brown/Sharp hydraulic surface grinder, Sunnen hone, and the coolant pump along with a bunch of other odds/ends (hardness tester, grinders, etc) in storage. I've run out of room here!

Brevard County? I lived at Patrick AFB as a wee lad back in 79-83. Great place for a snotty kid to grow up. Ocean on one side and the river on the other. Small world! Is "Penny Annie" subs still in the little strip mall in Sat Beach? or the Chinese place called Dragon Lady Inn? Pelican Point seafood restaurant still open in Cocoa?

Thanks for the kind words.

C

 

[UrbanMyth]

Re: Some barreling work.

Great post.

 

[Bryan27]

Re: Some barreling work.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">That'd be why I single point bore the hole behind the bullet's engagement point to the breech face. Since we know we are reaming a banana the center point changes an arbitrary amount at any given linear position. The reamer will do its best to follow whatever hole its shoved into. If the boring operation is done correctly the reamer will naturally want to run concentric to that hole as it feeds into the material- to the point that a pilot up front really isn't even needed. I've tested and proven that one as well. When I get to the new building and have the room for my "psychomatic" high pressure/high volume coolant pump I plan to run my reamers pilot free so that I have more fluid delivery through the nose of the tool.

All I'm wanting to do is keep the bearing surface of the bullet as tangent to the bore as I can. Assuming the loaded ammunition is reasonably good the rest should follow along accordingly.

Thus far I've seen no reason to change the process. Everything is coming out pretty dern good. Guns shoot very well, they still run fine (feeding/extraction) and customers are very pleased. All pointing in the right direction.



</div></div>

I've been reading this thread with great interest, several times and somehow I managed to miss it in your second post where you said, <span style="font-style: italic">"Once I get to where the action will go onto the barrel just enough to not stick a thread I skip through the rest of the passes and move onto boring the breech/chamber to get it concentric for the reamer."........</span>It makes all the sense in the world now! I had my mind wrapped around the idea of the pilot following the banana shaped hole and throwing off the chamber dimensions, which it would still do even if you dialed it in in two places. What I was stuck on was if the pilot was following the banana shaped bore, then it wouldn't really matter where you indicated from....the chamber would end up concentric with the ending point of the pilot, but would be dimensionally incorrect and tapered "open" the closer you get to the breech. Hell, it even occurred to me that you could single point cut the bore to straighten out the banana and I just didn't see where you already said it. I need some glasses!

When you single point bore the chamber, are you just removing enough material to make the length from your indicated point to the breech concentric or do you go on and single point "rough" the chamber while you're in there already? I have wondered if it would be doable to bore a chamber with a CNC turning center rather than ream the chamber. Write a program for the chamber dimensions and let'r rip? I imagine tool distortion wouldn't allow it, but I'm not up to speed on what's all out there either, I'm sure someone could figure it out. Thanks for taking the time to post all this and answer my stupid questions.

Bryan

 

[LRI]

Re: Some barreling work.

The only time I've ever single pointed a chamber was a long time ago on a 9mm rimfire shotgun. It was a pre WWII Anschutz "rat gun" used for "weeding" the garden/barn of pests. A vet brought it home demilled and when he passed it was given to a grandson and he sent it to me to restore.

Tool deflection would certainly be the big item to overcome with something like this in a centerfire cartridge. I think even a solid carbide boring bar would have problems. I use the CXS series of inserted solid carbide from Sandvik and while they are quite good (awesome actually) the small ones are prone to squealing when the reach gets much past an inch.

Thanks for the kind words.

Chad

 

[border_reiver]

Re: Some barreling work.

Yeah, you could probably get away with boring the case body, but as you said tool deflection once you get into the meat and potatoes could prove reliably unrepeatable. Hard to go wrong with a piloted form tool for that particular feature.