Re contouring a barrel blank

[turkn8r1]

Hey folks I have a probably dumb question but here goes anyway. I have a 30 cal button rifled barrel blank. It is 32" rough length 1.250" and it is fluted (straight flutes). Can it be re contoured to say a Sendero contour. or am I stuck with what I have. Not trying to start anything just an honest question. FWIW I have already ordered another barrel for my re barrel. If I can't use it i guess I will sell it. It is a Pac-Nor. Thanks in advance.

 

[J E Custom]

Yes with a few qualifiers.
Depending on how deep the flutes are, and how much shank you want.

Typically, straight barrel need some contouring. With this one being fluted, the chances are that it is straight. (No Runout).

J E CUSTOM

 

[tim_w]

I agree if it was properly stess relieved its doable. What mamf will tell you alot.

 

[sable tireur]

I have a 30 cal button rifled barrel blank. It is 32" rough length 1.250" and it is fluted (straight flutes). Can it be re contoured to say a Sendero contour. or am I stuck with what I have. It is a Pac-Nor.

If this is a button rifled barrel which Pac-Nor is, no matter what the contour is, I don't recommend any contouring at all. Button rifling adds an enormous amount of stress to the finished barrel. Contouring after rifling unloads some of the stress and the barrel can warp or change shape.

Sell this one as is since you need to get another contour and be happy when the new barrel arrives and you don't have to do any more work except thread, chamber and crown.

Enjoy the process!

Regards.

 

[J E Custom]

I did not know that "all" buttoned rifles were not double stress relieved. the billet comes from the mill stress relieved and then after the barrel is drilled and rifled, it receives another stress relief then it is lapped.

It is standard procedure for most to stress relieve after the buttoning process to remove these stresses. This normally adds 2 weeks to the delivery but is worth the wait.

Cut rifling does not require the second stress relieve, but sometimes the billet may not be fully stress relieve and the second stress relief assures that it is correct.

J E CUSTOM

 

[sable tireur]

Agree or disagree as you wish. Go ahead and put your money into a button rifle blank which claims to be 'double stress relieved' and then contour on your equipment but record the starting dimensions accurately as well as the interior curvature form from breech to muzzle. Most gunsmiths aren't equipped to do this which is why you see so few incidents of rejected re-contouring. The new technologies applied to the older manufacturing techniques often open a lot of eyes to what really takes place.

Measured accurately and recorded then contoured, then remeasured, you will discover that there will always be a shift from the original shape with button rifled barrels.

I don't offer this as an opinion but from someone who has made barrels for a living and has tested nearly every makers offerings with regard to their claims.

Do as you see fit.

Enjoy the process!

 

[mtbullet1]

Agree or disagree as you wish. Go ahead and put your money into a button rifle blank which claims to be 'double stress relieved' and then contour on your equipment but record the starting dimensions accurately as well as the interior curvature form from breech to muzzle. Most gunsmiths aren't equipped to do this which is why you see so few incidents of rejected re-contouring. The new technologies applied to the older manufacturing techniques often open a lot of eyes to what really takes place.

Measured accurately and recorded then contoured, then remeasured, you will discover that there will always be a shift from the original shape with button rifled barrels.

I don't offer this as an opinion but from someone who has made barrels for a living and has tested nearly every makers offerings with regard to their claims.

Do as you see fit.

Enjoy the process!

how does this change in interior curvature affect anything?

 

[J E Custom]

Some might think that I am a buttoned rifling guy, But not so.
I use both typs of barrels depending on the need and requirments. Both have there strong points if the proper one is chosen it will perform well.

If you chose a cut rifled barrel that Is not stressed relieved properly, It will give you many headakes. The same is true for a buttoned rifle barrel, and If the manufacture does not do a follow up stress relieif it will give you trouble also.

Cheep brands of rifle barrels are no bargin because they skip many steps to save cost. they generally use the same materials as do the top brands, so the blanks cost the same. Only the quality and requirements are more stringent with the top quality barrels.

I re-contour alot of barrels for just as many reasons and a poor barrel is just that, a poor barrel, no matter the type of rifling. It is very important to verafi the quality control of a barrel maker to get what you pay for.

Some of the buttoned rifling makers void the warenty if any countouring or fluting is done to there barrel. (This tels me that they may not stress relieve after the button process) but I have also seen cut rifled barrel go bad if they were altered in any way. (This tells me that they did not check each blank for proper stress relief before rifling.

Now days the order of the day seems to be to cut corners and/to save cost. "You Get What You Pay For as long as you demand it).

J E CUSTOM

 

[yobuck]

Pac nor will recontour a barrel if sent to them as ive had it done by them with a different brand barrel.
So id be calling them about it.
Ive also had Hart redo as I recall 2.
Brux also turned a new in stock barrel to my specs before shipping it to me. I think it was the most accurate barrel ive ever owned.
Im told that barrel makers grind as opposed to turning, which might make a difference.

 

[shortgrass]

yobuck, I believe the machine tool of choice these days is a lathe similar to, if not, the Haas TL series of CNC lathes. After turning, the barrel is put on a barrel spinner and 'polished' against a belt sander. You might be surprised how nice of a finish that you can get , straight off of a properly tooled machine, these days. Before the CNCs, there were 'tracer' lathes, where a sensor followed a 'pattern'. Regardless of what kind of lathe, current practice is to use a pneumatic follow rest to help prevent deflection. Grinding is just too slow.

 

[J E Custom]

yobuck, I believe the machine tool of choice these days is a lathe similar to, if not, the Haas TL series of CNC lathes. After turning, the barrel is put on a barrel spinner and 'polished' against a belt sander. You might be surprised how nice of a finish that you can get , straight off of a properly tooled machine, these days. Before the CNCs, there were 'tracer' lathes, where a sensor followed a 'pattern'. Regardless of what kind of lathe, current practice is to use a pneumatic follow rest to help prevent deflection. Grinding is just too slow.

I countour on a Lathe and dont want to sand or grind at all on the lathe because of the abraisave dust that gets on everthing. It will excelerate wearing of ways, lead screws and anyother moving parts. If I have to do any sanding or grinding, I cover the ways and lead screws with paper towels to keep the grit off my lathe and remove it very carefully
when done.

This requires specal tooling and spindle speeds to end up with a finished cut that needs no sanding or grinding. Mostly, I use carbide tools for ruffing and high speed tools for finishing. if everything is done right, the barrel will end up with a very nice finish and won't require any sanding or grinding.

The last contouring cut requires a .005 to .007 thousandths cut with a specially ground high speed tool. (Carbide doesn't like to take this light of a cut and will not do as nice of a finish) so the high speed tool is the best choice. I have not tried the shear grind on the finish tool yet, but If anyone has,comments would be welcome . The reason the manufactures sand/grind the finish on there barrels is because they use carbide tools to contour and take large cuts for speed, so the finished cut is less than desirable and has to be sanded. It is common to find flat spots where the sanding was not done correct on some custom barrels. You can feel or the dial indicator will show these places when rotated between centers even though the eye cannot see them.

Grinding tools has almost became a lost art with all of the pre-ground tools and CNC machines and I find it very satisfing when I grind a tool for a special use and it does realy well.

J E CUSTOM

 

[msalm]

For all the naysayers on re-contouring a button rifled barrel, you do realize they are contoured after rifling by the manufacturer (and most often after a second heat/stress relief). If you choose to turn it down some more, it's nothing that doesn't happen anyway. Sure you might want to cast a lap and ensure the muzzle didn't grow on you but that can be lapped back too. I've read all the cautionary tales of what might happen, but have never experienced any ill effects and only read of a few. The reality is the vast majority of recontoured barrels shoot just fine to as good as they did originally.