Bore run out in a new barrel

[JRB]

A friend a I have just finished chambering our second barrel, so we are very new to this,
Both barrels are in 20 cal, one chambered in .204 and the other in 20 PPC.

We have set up the barrels in a 4 way adjustable pipe, in the 4 way chuck and used the range rod to reduce the run out of the bore to just about zero before we start.
Now the finished result, looks real nice and has worked very well, the result has been better than we could have hoped, but i have two questions,

1. in getting everything perfect at the chamber end, at both ends of the exposed range rod, we than removed the rod and proceeded to start the chambering, after we had finished, we fitted it to the muzzle end, and noticed that the first barrel had .024" runout. As this was our first barrel we did not think much more about it as the chamber end was spot on. we did not index it, so it is sitting at about 10 o'clock?

2. With our second barrel we set it all up, ready to chamber, and then checked the muzzle end, and found the run out to be .040", so we indexed it to 12 o clock, and then chambered the barrel.

What it an acceptable amount of run out for a bore, at what stage dos it affect the accuracy?
Do you always index the barrel, to 12 o clock?

Jim

 

[JerrySharrett]

How did you index it before you chambered it?

If you are going to do the GG method you will have runout, some much greater than what you posted.

 

[alinwa]

To JRB.... I always index prior to chambering and I use settings near to the vertical plane. I have had barrels bent so badly that they were 30" off at 100yds that shot perfectly........ you get the vibrations right and there's no barrel "too crooked" IMO

In fact, I've got a hangup with straight barrels. I WILL trade my straight ones straight out for anybodies crooked one any day.

"bent barrels shoot best"

al

 

[JerrySharrett]

To JRB.... I always index prior to chambering and I use settings near to the vertical plane. I have had barrels bent so badly that they were 30" off at 100yds that shot perfectly........ you get the vibrations right and there's no barrel "too crooked" IMO

In fact, I've got a hangup with straight barrels. I WILL trade my straight ones straight out for anybodies crooked one any day.

"bent barrels shoot best"

al

al, how do you index before chambering when the action is glued in?

 

[JRB]

Thank you for the reply's
The method we used to index the bore,
we removed the range rod from the chamber end once everything was as close as possible to true.
Then inserted the rod in the muzzle, and set up the dial indicator to gain a reading. Using the dial gauge we determined run out. We than used a texta to mark the barrel at the chamber end to index with the action.
Jim

 

[f21sh]

They do wobble don't they

Just chambering a Shilen currently it wobbles .035" IR. However the chamber end in the throat area IR is currently @ 0.0003" I'm still try to get the indicator to not move at all the IR should be equal to or less than 0.0002" at that point. It takes time. Attempting to get it as straight as possible.

 

[geo.ulrich]

To JRB.... I always index prior to chambering and I use settings near to the vertical plane. I have had barrels bent so badly that they were 30" off at 100yds that shot perfectly........ you get the vibrations right and there's no barrel "too crooked" IMO

In fact, I've got a hangup with straight barrels. I WILL trade my straight ones straight out for anybodies crooked one any day.

"bent barrels shoot best"

al

Al, There seems to be some validity in this I have kind of noticed a trend in crooked ones working better also...George

 

[dmoran65]

To JRB.... I always index prior to chambering and I use settings near to the vertical plane. I have had barrels bent so badly that they were 30" off at 100yds that shot perfectly........ you get the vibrations right and there's no barrel "too crooked" IMO

In fact, I've got a hangup with straight barrels. I WILL trade my straight ones straight out for anybodies crooked one any day.

"bent barrels shoot best"

al

Glad to hear I'm not the only one who wonders about this......
One of my very best "raw accuracy" barrels was far from a straight line bore, that always keeps me wondering.

D

 

[alinwa]

al, how do you index before chambering when the action is glued in?

I can sometimes take measurements off the old barrel but mostly I make an action jig. It doesn't take too long, throw a hunk of tubestock in the lathe, run a set of through-threads and face it to an index point "like the action." Several times I've been lucky enough to have another action present, and lately I've taken to making tenon facing jigs indexed and faced to proper depth.....These tenon jigs or sleeves are real time savers for the next job(s).

It's all easy but time consuming. I currently do this as a hobby, hoping that the time spent making the jig is paid for by the job... the old "doing the job to get the tool" conundrum.

I have no trouble chambering last because I've mounted a DRO on my tailstock quill.

Admittedly though it's much harder to get multiple chambers done identically on a glue-in. I really do like to set my final headspace by 'feel' as I don't measure probably as well as you more experienced guys do. In fact, I hate to measure AT ALL preferring to jig or gage everything.

al

 

[B.Larson]

Crooked bores

do a search on this site...."Chucking up a Barrel Part Deux".....this topic has been discussed here...years ago...... many companies straighten barrels..with crooked bores...pistol,rifle,shotgun and howitzer barrels..... I believe Griffen and Howe did it,savage does it....google the subject.
Is it worth it..... to straighten...???.....
I don`t.....
bill larson

 

[JerrySharrett]

I can sometimes take measurements off the old barrel but mostly I make an action jig. It doesn't take too long, throw a hunk of tubestock in the lathe, run a set of through-threads and face it to an index point "like the action." Several times I've been lucky enough to have another action present, and lately I've taken to making tenon facing jigs indexed and faced to proper depth.....These tenon jigs or sleeves are real time savers for the next job(s).


al

I know Kelblys uses an indexing sleeve for some of the very old Pandas that were not synced so the barrel marking would come up in the correct place.

I really don't understand that if the GG method adds to accuracy, and no one has shown proof yet, why go through these extra steps then have to chase he sighting-in shots all over the county??

Using a method where the chamber neck and the muzzle bore are dialed in closely, changing barrels requires just a very few clicks to be zeroed again!!

 

[JRM850]

To JRB.... I always index prior to chambering and I use settings near to the vertical plane. I have had barrels bent so badly that they were 30" off at 100yds that shot perfectly........ you get the vibrations right and there's no barrel "too crooked" IMO

In fact, I've got a hangup with straight barrels. I WILL trade my straight ones straight out for anybodies crooked one any day.

"bent barrels shoot best"

al

There used to be one of these barrel benders at the Colorado School of Trades, but we were never taught to use it.

If someone could locate one it would make for a really interesting experiment to chart the effect on accuracy as more bend is added. It makes some sense to me that a perfectly straight barrel might have a more random vibration pattern.

 

[JerrySharrett]

That barrel straightener looks like one still in use in a SE barrel makers shop. They look through the barrel and at a dot/light and then rotate the barrel.

As to perfectly straight, ain't airy. I'd take my chances on a barrel that hasn't had any post rifling manipulations and profile turning makes me wonder. I do like post riffling sub-zero treatment. When a barrel gets hot and it has residual stresses it will react to those stress changes, fact!

 

[DSM]

I'm still confused as to indexing a barrel in a lathe. I have yet to chamber, but will shortly once I gather a reamer and pilots.

Anyhow, this is how I understand it and please correct me if I'm not looking at it the right way. I will be using two spiders, one on each end of the head stock. I will dial in the muzzle end, dial in the breech and then set he dial back at the muzzle and mark the high spot. This cool?

 

[alinwa]

I know Kelblys uses an indexing sleeve for some of the very old Pandas that were not synced so the barrel marking would come up in the correct place.

I really don't understand that if the GG method adds to accuracy, and no one has shown proof yet, why go through these extra steps then have to chase he sighting-in shots all over the county??

Using a method where the chamber neck and the muzzle bore are dialed in closely, changing barrels requires just a very few clicks to be zeroed again!!

???Chase???

I don't chase NUTTIN.... I KNOW where I'm pointed e'er shot is ever fired.

And I have personally had to lap over 1 set of Talley's on a barrel chambered between centers on the best, by the best because it was 18moa off diagonally. This was not "my work" nor was it any "fault" of the guy doing the work. "The Work" was faultless but that pertickler barrel was wickkid bent.

Would I ever even dream of straightening a real barrel???


Good Heavens NO!!!


silliness

But I do establish where a barrel points and use the information, wisely.

al

 

[alinwa]

BTW, 21" 6mm barrels with s minimal contour are often quite straight. I'll agree that 90% of the time you can spin them up between centers and be within a couple inches. But start messing with skinny/fluted/long tubes and this all changes!

An awful lot of short range gunsmithing technique (and reloading technique) falls short when stretching to many hundreds of hards.

 

[Matt P]

Al
Say the barrel has 0.020" run out @ the muzzle (30" barrel) how far away from 0 would be the point of impact ?

Regards
Matt P

 

[JerrySharrett]

Indexing is quite simple really. You take a barrel that the business end is wobbling like a drunk sailor in a hurricane and point that wobbly part to the 12 O'clock position in your lathe. Then you turn the spindle on and proceed to chamber the other end...


Sorry, I couldn't resist!!

 

[clowdis]

I'm going to take a different direction than most of you in regards to the GG method of centering up a barrel. I have used this method and I don't use it any more. When the breech end of the barrel is clamped in the chuck with a wire or bar to allow it to swivel it must be left less than an optimal tightness for turning and chambering to allow it to swivel when you adjust from the spider. If it is too tight in the chuck you will bend the barrel with the screws in the spider. I look at the TIR at the muzzle end of some of the barrels that I've done this way (especially sporter weight barrels) and say to myself "no freakin way". The bores can't be this bad. So the barrel has to be warped or bending somewhere. If I continue with chambering a barrel set up this way I can check again later in the machining and find that my setup isn't any good anymore. The bend has come out and the barrel is no longer running on centerline. Now I just use a pin in the bore of the breech end to center the bore and indicate the muzzle to .000 TIR and go with it. If I need to determine which point of the barrel needs to be up I put a pin in the muzzle end and indicate the high spot on the pin and mark it on the barrel. It is almost never as bad as it would be if I try jacking around the muzzle end before chambering. To each his own I suppose, but I just believe that it's too easy to get misalignment using the GG method if you aren't careful about getting the barrel in a bind.

 

[B.Larson]

I'm going to take a different direction than most of you in regards to the GG method of centering up a barrel. I have used this method and I don't use it any more. When the breech end of the barrel is clamped in the chuck with a wire or bar to allow it to swivel it must be left less than an optimal tightness for turning and chambering to allow it to swivel when you adjust from the spider. If it is too tight in the chuck you will bend the barrel with the screws in the spider. I look at the TIR at the muzzle end of some of the barrels that I've done this way (especially sporter weight barrels) and say to myself "no freakin way". The bores can't be this bad. So the barrel has to be warped or bending somewhere. If I continue with chambering a barrel set up this way I can check again later in the machining and find that my setup isn't any good anymore. The bend has come out and the barrel is no longer running on centerline. Now I just use a pin in the bore of the breech end to center the bore and indicate the muzzle to .000 TIR and go with it. If I need to determine which point of the barrel needs to be up I put a pin in the muzzle end and indicate the high spot on the pin and mark it on the barrel. It is almost never as bad as it would be if I try jacking around the muzzle end before chambering. To each his own I suppose, but I just believe that it's too easy to get misalignment using the GG method if you aren't careful about getting the barrel in a bind.

Couldn`t agree more. It`s very easy to bend a barrel using an outboard spider,Especially if you don`t allow the breech end to pivot.