Gunsmithing Re-contouring a barrel blank

[Blackcreek]

Due to not all barrel contours being available from the manufactures that I would like to use I'm asking about re cutting or contouring a new barrel blank. It looks like some of the straight contours or heavy m24 type blanks are available but not a varmint or sporter profile.
I have a cnc lathe so turning a different taper on a blank shouldn't be a problem but I've heard and read conflicting things regarding doing it.

I've read it's ok to re-contour a cut rifle barrel because they don't have the internal stress that a button rifle barrel has but I'm not sure how true this is. Same thing with fluting a finished contour barrel it's ok on cut rifle but not button rifled.

I tend to like Bartlein barrels for center fire not for any particular reason just always heard good things about them. I have done Shilen ratchet barrels on rimfire as they seam to dominate rimfire benchrest which is what I used to shoot.

Any advice on speeds and feeds and depth of cut for turning the contour on a barrel
IPR ?
RPM ?
DOC ?

 

[Huskydriver]

@Frank Green

 

[b6graham]

@bohem

 

[Jrb572]

I have an AR 10 that APA contoured the barrel blank for and it shoots extremely well.

 

[JBoomhauer]

I am not a gunsmith but there are way too many variables to give an answer.

For best luck qualify stock and steady rest.
Follower rest if no taper and held to decent tolerances.
Speeds and feed starting points will come from your insert mfg.

Length and diameter matter. 26-30xD without support will leave you very unhappy.

And it is usually IPR for lathe.

 

[Blackcreek]

edit for IPR yes that's right slight oversight on my part.

No steady or follow rest on my Haas so that could be a challenge. Had thoughts of turning it between centers but it could also be done 1/2 at a time in the chuck to cut down on vibration and length of stick out.

 

[Threadcutter308]

edit for IPR yes that's right slight oversight on my part.

No steady or follow rest on my Haas so that could be a challenge. Had thoughts of turning it between centers but it could also be done 1/2 at a time in the chuck to cut down on vibration and length of stick out.

You’ll find out quickly that an unsupported barrel in the center will start oscillating pretty quickly. You’ll also find that tool deflection will probably be an issue.

I’ve done it, but it’s a PITA and makes more sense to just buy a new barrel of the proper countour. Much cheaper/easier in the long run.

 

[DeathBeforeDismount]

There are VERY few smiths I would trust this to. One who CAN and does do this, and knows what he is doing is Greg at Southern Precision Rifles aka bugholes. He also has some of the fastest turn around times, but you will pay for it.

 

[whatsupdoc]

Button rifled barrels are contoured after the button is pulled through and plenty
of guys have built rifles that don't meet weight and have the barrel re-contoured.

It is not an uncommon process.

 

[Leebedford]

Toss her in the lathe and go to town.

 

[4O6shootist]

Make sure you have a good follower opposite your cutting assembly to keep deflection and stress as low as possible.

 

[iceng]

Hydraulic follower. This is one way of doing it. You really need machines specifically designed to do long shafts.

 

[Frank Green]

Due to not all barrel contours being available from the manufactures that I would like to use I'm asking about re cutting or contouring a new barrel blank. It looks like some of the straight contours or heavy m24 type blanks are available but not a varmint or sporter profile.
I have a cnc lathe so turning a different taper on a blank shouldn't be a problem but I've heard and read conflicting things regarding doing it.

I've read it's ok to re-contour a cut rifle barrel because they don't have the internal stress that a button rifle barrel has but I'm not sure how true this is. Same thing with fluting a finished contour barrel it's ok on cut rifle but not button rifled.

I tend to like Bartlein barrels for center fire not for any particular reason just always heard good things about them. I have done Shilen ratchet barrels on rimfire as they seam to dominate rimfire benchrest which is what I used to shoot.

Any advice on speeds and feeds and depth of cut for turning the contour on a barrel
IPR ?
RPM ?
DOC ?

Are you using a steady rest? If not chatter could be a big problem.

What varmint or sporter profile are you looking for?

We do more contours than what is listed on our website. We could've made that page 12 pages long. If you don't see a contour listed you just have to call and ask.

Later, Frank
Bartlein Barrels

 

[Blackcreek]

My question was more of a hypothetical scenario of being able to order a heavy profile from a third party vendor and have it immediately and just turn it vs ordering one and waiting a few months for it.

 

[b6graham]

My question was more of a hypothetical scenario of being able to order a heavy profile from a third party vendor and have it immediately and just turn it vs ordering one and waiting a few months for it.

just order a barrel from someone who does it in house already (bugholes for cost, PVA it's included)

 

[Frank Green]

just order a barrel from someone who does it in house already (bugholes for cost, PVA it's included)

To my knowledge Bugholes does not recontour. I could be wrong but they order everything from us as contoured normally.

 

[strikeeagle1]

From the peanut gallery, I would be commissioning the likes of Mr. Green to contour my barrel. OP might consider getting an inexpensive barrel blank to trial contouring on his CNC machine, then compare the two ex post facto.

 

[ForgeValley]

Greg (SPR) has recontoured quite a few barrels for me.

 

[JBoomhauer]

From the peanut gallery, I would be commissioning the likes of Mr. Green to contour my barrel. OP might consider getting an inexpensive barrel blank to trial contouring on his CNC machine, then compare the two ex post facto.

I wouldn’t. I would wait until a run of the desired contour is in the pipeline, then just swap it out.

Maybe even charge a “re-contour” fee.

A one off is very expensive compared to making a run of parts.

 

[Frank Green]

Greg (SPR) has recontoured quite a few barrels for me.

We’ve done custom contours for him as well. In some cases we will do most of the contour work and he does the final touch up so the barrel will fit the stock inlet properly or have something to do with fitting specific items to the build and you need all the parts in front of you while doing the work.

 

[Frank Green]

I wouldn’t. I would wait until a run of the desired contour is in the pipeline, then just swap it out.

Maybe even charge a “re-contour” fee.

A one off is very expensive compared to making a run of parts.

The contour has nothing to do with the run per se. We contour the barrels 90% of the time or more before reaming and rifling etc…

Yes we have received barrels back on customers and recontoured them for the customer for a fee. Just got one in today from an ammo maker. They had one of our 1.250” straight blanks. Now it will become a modified Barrett MRAD contour. Plus all the chamber and threading work to go with it.

 

[Frank Green]

Hydraulic follower. This is one way of doing it. You really need machines specifically designed to do long shafts.

Looks like a Schunk steady rest. That’s what we run. Made in Germany. You can run them hydraulic or with air pressure.

 

[bohem]

I will recontour your barrel for $60 or you can give me your requested contour and we can cut a blank that I have in stock here. If it's not in our list of standards then the contour price will be quoted with the blank, it's typically about $25 unless you're looking for a toothpick that I'll have to run for 40 minutes.

Quite literally every button barrel that I've cut in the last 5 years has been contoured in house, going on 10,000 of them. Our "bad barrel" reject rate is under 0.5%. Yes, Bartlein is a much bigger operation than we are but I think we've gotten enough data at this point to make a statistically significant analysis of our experience. No, I'm not attempting to argue with Frank and what they do there. Bartlein makes great stuff, they do it differently than I do.

Button barrels can be contoured/recontoured so long as the material is properly stress relieved to start, which is a requirement of a good barrel anyway. Buttons do like being rifled in the uncontoured state and then contoured AFTER being properly normalized, but properly normalizing is paramount to a good barrel anyway so it's a moot point by the time a chamber reamer sees that breech.

 

[DeathBeforeDismount]

To my knowledge Bugholes does not recontour. I could be wrong but they order everything from us as contoured normally.

Last time I talked to Greg, he told me if they only had it in a 1.3 instead of a 1.25 barrel, he would recountour it down.

I think it has more to do with availibility. Such as certian bore and twist rates being in stock vs waiting a year.

 

[Earnhardt]

I have an AR 10 that APA contoured the barrel blank for and it shoots extremely well.

Was it on an unchambered barrel blank? Or was it a pre-chambered, heavy contoured barrel you profiled into a smaller profile? Thanks.

 

[ACard]

I will recontour your barrel for $60 or you can give me your requested contour and we can cut a blank that I have in stock here. If it's not in our list of standards then the contour price will be quoted with the blank, it's typically about $25 unless you're looking for a toothpick that I'll have to run for 40 minutes.

Quite literally every button barrel that I've cut in the last 5 years has been contoured in house, going on 10,000 of them. Our "bad barrel" reject rate is under 0.5%. Yes, Bartlein is a much bigger operation than we are but I think we've gotten enough data at this point to make a statistically significant analysis of our experience. No, I'm not attempting to argue with Frank and what they do there. Bartlein makes great stuff, they do it differently than I do.

Button barrels can be contoured/recontoured so long as the material is properly stress relieved to start, which is a requirement of a good barrel anyway. Buttons do like being rifled in the uncontoured state and then contoured AFTER being properly normalized, but properly normalizing is paramount to a good barrel anyway so it's a moot point by the time a chamber reamer sees that breech.

@bohem I have a Schneider hvy varmint 6.5 with P5 rifiling barrel blank, while I love Schneider barrels the finish is always rough as a cobb. Would you consider, for a fee of course, cleaning that up for me and possibly removing just a bit of metal?

 

[Jrb572]

Was it on an unchambered barrel blank? Or was it a pre-chambered, heavy contoured barrel you profiled into a smaller profile? Thanks.

They said I was a 30cal blank

 

[bohem]

@bohem I have a Schneider hvy varmint 6.5 with P5 rifiling barrel blank, while I love Schneider barrels the finish is always rough as a cobb. Would you consider, for a fee of course, cleaning that up for me and possibly removing just a bit of metal?

Sure. Send me an email to discuss please
[email protected]

 

[ACard]

Sure. Send me an email to discuss please
[email protected]

Roger that, will do.

 

[Yondering]

I make a lot of my barrels from blanks (maybe 20 or so at this point, peanuts compared to somebody like Frank Green) and have recontoured a handful of factory heavier barrels as well. My 2 cents:

It's fun to do yourself and a great learning experience, so it's worth a try on an inexpensive barrel at least, since you have your own lathe. I wouldn't try to learn on a high end barrel though. But there are some pitfalls, chiefly vibration as mentioned earlier. With an AR barrel an easy solution is to turn it in two sections, divided by the gas block journal. With a tapered bolt action barrel that's more difficult though; clamping the chuck on a tapered section of barrel has it's own issues, and any time you turn a shaft, even a straight one, in two sections there's always a likelihood that the two sections won't match up correctly.

One way I've done it is to make fairly heavy cuts at low speed in back gear (i.e. about 200 rpm or slower) to rough out the shape within a few thousandths, then use the very sharp "aluminum cutting" carbide inserts to finish it. When the finish cut is only a few thousandths deep vibration is not as much of an issue. I've also used gentle hand pressure as a "soft follower" on the barrel to eliminate vibration; it doesn't take much. Sometimes a small patch of leather is handy for this depending on the finished surface, just make sure it's not something big enough to catch on the barrel and wrap up your hand; there is some danger involved with this so be careful.

About fluting - I've done a bit of that as well, and my best advice is to do it in increments, rotating around to cut each flute to a certain depth in a pattern like you'd tighten lug nuts on a wheel. Maybe something like .020"-.030" deep on each flute, then start back at the first one again and cut to the next depth, etc and leave the final pass to about .005" or so. This seems to give more consistent results than just cutting each flute to full depth before moving to the next. Of course production machines designed for this will do it differently, but the above advice is based on working with home shop machines like a Bridgeport and common 12"-14" lathes.

Hope that helps.