This is how much an ID can be crooked in even a premium barrel.

[jackieschmidt]

I set up a new 1-17 30 caliber barrel this morning to chamber in 30BR.

I cut it to the 22.5 inch length, taking all of the length off the muzzle end.

When I chucked the barrel up to thread it for the crown and tuner, The OD would just barely true up within the range of my Set True Chuck, which is .015 inch.

in just 6 inches, this the ID was running out close to .012 inch from the OD. After I Got it true on both ends, this part part looked really true with its own self. However abut 2 or 3 inches from the throat, it had another spot that looked about this bad.

The Gun drill kinda took a mind of it’s own as it progressed through this blank.

I’m going to shoot it. You never know.

The ID between centers shows the runnout on the end I cut off. The original is in the Chuck Center. The OD and ID run dead true on that end.

 

[AlNyhus]

Jackie, my bet is that it will shoot fine. I still have a Kostyshyn 1:17 that gets that wonky 2" ahead of the throat. It was a killer good barrel.

I know you do routine throat freshen ups..might be the one hiccup.

 

[WayneShaw]

Kostyshyn's would make you sea sick looking down the barrel while spinning, but they sure did shoot!

 

[CJ6]

What do you think would cause this ? Hard or soft spots in material or feed speed of cutting tool ?

 

[Jonnyofalltrades]

I have heard that gun drills that don't have a counter rotating spindle are more prone to wandering....

 

[DaveTooley]

I have heard that gun drills that don't have a counter rotating spindle are more prone to wandering....

A lot of top shelf barrels are drilled with old Pratt Whitney's.

 

[Will Henry]

It could be a hard or soft spot, an inclusion, or simply a chip temporarily welded to the bit. If the guide is a bit loose, the bit may not get a straight start. Since the bit is influenced by the body of the bit running on the drilled hole, a bad start is perpetuated. There are a lot of those old Pratt and Whitney's in use. In fact, all of the barrel making shops I have visited had at least one. By the way, in the last fifty years, I have seen exactly one barrel which appeared to be perfectly straight. It wasn't absolutely perfect either. When I cut off four inches, it showed nearly four tenths TIR. It was beautiful barrel which shot OK. WH

 

[Jonnyofalltrades]

A lot of top shelf barrels are drilled with old Pratt Whitney's.

Yes, I believe Lilja runs two of them, rebuilt.
I read somewhere where Dan Lilja said that he was able to regularly have the drill exit within 10 thou of center. What it does in between is another matter, perhaps.

 

[DaveTooley]

Kreiger and Bartlein use them. Like most things in our precision world there is some art to what we do.

 

[jackieschmidt]

The straightness of the barrels ID is predicated on the path that the Gun Drill decides to take as it proceeds through the blank.
Every post drilling operation follows that hole.

The reason I posted this is I have never had what I called a premium barrel show anything near this type of run out. When cutting this far up the profile to make weight, I have seen the bore be out 2 or 3 thousandths, but never .012.

And I have done a lot of barrels.

 

[ChrisNZ]

..in the last fifty years, I have seen exactly one barrel which appeared to be perfectly straight...

Ironically, the straightest barrel my (now deceased) gunsmith reckons he ever saw was a Norinco rimfire I got him to put a suppressor on for my nephew. Shot well too.

A way-less-than-straight .30 cal Broughton I had fitted to my son's FTR rifle is an absolute tackdriver. My gunsmith indexed it "exit up" to avoid windage zeroing issues. Don't think barrels have to be straight to shoot well.

 

[L.Sherm]

Do you guys think there's any correlation to how wide or narrow nodes are to a straighter barrel vrs more run out?

 

[JPB3]

Years back I was doing a barrel and it offered up .017 of ID to OD runout.. Pulled it out of the lathe, it's still under my bench.

 

[urbanrifleman]

Doesn't mean a thing.

 

[jackieschmidt]

Doesn't mean a thing.

I tend to agree. Everything else looked great, the bore, the grooves, all even an on size as advertised.