Gunsmithing bore curvature

[eddief]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrm850</div><div class="ubbcode-body">Spider stress... I'm seriously thinking about just using the action trueing fixture for this dasher I'm about to chamber. Anyone else do it this way? </div></div>

It will work and work quite well, but you have to be a little more careful, as it is further away from the chuck/spindle. Therefore, less rigid.

Just check your work very often to avoid problems.

 

[DAVETOOLEY]

Re: bore curvature

I chambered 750 barrels just last year. I used two 4 screw spiders and a long stem indicator. Reamer pusher. Complaints zero

YMMV

 

[JJones75]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I chambered 750 barrels just last year. I used two 4 screw spiders and a long stem indicator. Reamer pusher. Complaints zero

YMMV </div></div>

do you dial in zero only at the chamber end? for instance have the bore running true at the back end of the chamber and the throat area?
this is what i was taught was the best way to ensure the bullet starts into the grooves squarely and the muzzle end was only worried about when finding the highspot , untill the muzzle was crounded and or threaded then it was indicated in just like the chamber end

 

[JJones75]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I chambered 750 barrels just last year.
</div></div>

Damn impressive by the way.!!

 

[Straight Shooter]

Re: bore curvature

When the barrel is dialed in on the throat and 2" farther forward there is no need to look down the bore to see the curve. They wave around a lot more than that. Just set up an indicator on the muzzle end and spin it to the high point and mark it. That is where we time it straight up when the action is fitted.

I couldn't engrave the caliber on 750 barrels a year. Just to open the box and do our preinspect takes an hour. If I rejected it to box it back up and go print another shipping label is another 30 minutes. For us as a two man shop to complete 50 rifles a year would be an amazing feat. I go blind in paperwork in half that many. I don't think I could even do the log entries on 750 in a year. I doubt even Chad with his super speed cnc equipment could fit 750 barrels a year. You have a regular factory going there Dave.

 

[eddief]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: *Straight Shooter*</div><div class="ubbcode-body">When the barrel is dialed in on the throat and 2" farther forward there is no need to look down the bore to see the curve. They wave around a lot more than that. Just set up an indicator on the muzzle end and spin it to the high point and mark it. That is where we time it straight up when the action is fitted. </div></div>

If the barrel is in a truing jig (like it was stated), chances are the barrel end will be inside the spindle and not out the backside of the headstock. You will have to look down the bore to see the curvature.

I have had some really straight barrels before that didn't just wave around. For the record, they didn't shoot any better than barrels with say .025" to .050" muzzle runout.

 

[DAVETOOLEY]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JJones75</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I chambered 750 barrels just last year.
</div></div>

Damn impressive by the way.!! </div></div>

Do we know each other? Seems like we may have eaten some mud bugs together with Geraci.

 

[DAVETOOLEY]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: *Straight Shooter*</div><div class="ubbcode-body">When the barrel is dialed in on the throat and 2" farther forward there is no need to look down the bore to see the curve. They wave around a lot more than that. Just set up an indicator on the muzzle end and spin it to the high point and mark it. That is where we time it straight up when the action is fitted.

I couldn't engrave the caliber on 750 barrels a year. Just to open the box and do our preinspect takes an hour. If I rejected it to box it back up and go print another shipping label is another 30 minutes. For us as a two man shop to complete 50 rifles a year would be an amazing feat. I go blind in paperwork in half that many. I don't think I could even do the log entries on 750 in a year. I doubt even Chad with his super speed cnc equipment could fit 750 barrels a year. You have a regular factory going there Dave. </div></div>

I'll bet Chad would surprise you. Those barrels are pretty much all I did last year.

I'll be glad to show anybody if they want to stop by. Had a guy in here today who is just starting out. He walked out shaking his head and mumbling something about how simple it is. I checked one chamber while he was here. The neck ran 0.0000" and the the other end ran TIR .0001" Mother Nature will find the center of a hole.

 

[eddief]

Re: bore curvature

Are you happy with the Haas Mr. Tooley?

 

[7mmRM]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eddief</div><div class="ubbcode-body">7mmRM,

Your TDC should be fine. If you ever want to check/verify yourself, mark TDC as you normally would. Pull that TDC marked barrel out and stick it in an action truing jig and dial in your two spots like you normally do by using the action truing jig jack screws, leaving the muzzle end completely alone.

Once dialed in, rotate the barrel as slow as you can in back gear on the lathe while taking a peek down the bore. You will be able to visibly see the curvature in the muzzle end, and should be able to tell if it's in the same TDC marked spot. No spider or jacking screws are near or on the muzzle end, so you know it's not being bent or torqued out of normal. </div></div>

10-4 Thank you.

 

[JJones75]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JJones75</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I chambered 750 barrels just last year.
</div></div>

Damn impressive by the way.!! </div></div>

Do we know each other? Seems like we may have eaten some mud bugs together with Geraci. </div></div>

No sir , it would certainly be an honor though!

Mr Don lives about an hr away from him and I go up their now and then to humble myself and enjoy some laughs. Honestly the last couple times I was up their it was to let my son try and wrangle some catfish from his pond

 

[DAVETOOLEY]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JJones75</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JJones75</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I chambered 750 barrels just last year.
</div></div>

Damn impressive by the way.!! </div></div>

Do we know each other? Seems like we may have eaten some mud bugs together with Geraci. </div></div>

No sir , it would certainly be an honor though!

Mr Don lives about an hr away from him and I go up their now and then to humble myself and enjoy some laughs. Honestly the last couple times I was up their it was to let my son try and wrangle some catfish from his pond </div></div>

Say hello to Don for me. We go back about 34 years. I'll never forget shooting the National Championships at Kelbly's in 1984. Nobody knew I was in the hunt for the 200 LV championship. Don was standing right behind when they posted the results. He ask if I had won. I didn't know so we saw it together. No congrats, no pat on the back. All he said was good Tony Boyer didn't get the Hall of Fame points. I beat Tony by .0001" in the aggregate. Good days back then. I watched Don, Tony, Jeff Fowler, Ed Watson and others do battle. They made everyone better.

 

[DAVETOOLEY]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eddief</div><div class="ubbcode-body">Are you happy with the Haas Mr. Tooley? </div></div>

In a word yes. I have it set up to do nothing but chamber barrels. My setup is essentially the same as a manual lathe. I had to improvise a few setups but I can't see, measure or shoot the difference so all is good.

 

[jrm850]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I chambered 750 barrels just last year... </div></div>

It would take me a couple of lifetimes for me to gain as much experience as you did in one year alone. I would also love to hear your thoughts about tight bores vs conventional. I've read the debates until my eyes hurt but can't weed out the fact from fiction. It would be great to hear an opinion that I trust.

 

[DAVETOOLEY]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jrm850</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I chambered 750 barrels just last year... </div></div>

It would take me a couple of lifetimes for me to gain as much experience as you did in one year alone. I would also love to hear your thoughts about tight bores vs conventional. I've read the debates until my eyes hurt but can't weed out the fact from fiction. It would be great to hear an opinion that I trust. </div></div>

I have very little experience with tight bores. Just my opinion but why would you want to distort a perfectly good bullet more by using a tighter bore? The material displaced by the lands has to go somewhere which means the bullet becomes elongated.

 

[jrm850]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">

I have very little experience with tight bores. Just my opinion but why would you want to distort a perfectly good bullet more by using a tighter bore? The material displaced by the lands has to go somewhere which means the bullet becomes elongated. </div></div>

I was kind of hoping you would say that. I was trying to decide of it was worth the wait for a tight bore or buy the one a forum sponsor had in stock. Thank you.

 

[Sniper Uncle]

Re: bore curvature

Very interesting thread. I really learned a lot about how little I actually know. Fascinating learning about curvature and indication in barrels. Some day I would love to learn gun-smithing.

 

[mcfred]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JJones75</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">I chambered 750 barrels just last year. I used two 4 screw spiders and a long stem indicator. Reamer pusher. Complaints zero</div></div>

do you dial in zero only at the chamber end? </div></div>

So Dave, with your comment about nature finding the center of a hole I take it that you indicate at both ends of the blank? (muzzle and back of where the chamber will be)

 

[DAVETOOLEY]

Re: bore curvature

McFred

You're correct. Throat and muzzle.

 

[Straight Shooter]

Re: bore curvature

These are some nice drawings from: 300sniper


<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">throat and muzzle at zero tir:

same picture, zoomed in on chamber end:

</div></div>


Dialing the throat and the muzzle; isn't that ignoring the curve of the bore and chambering out of line with the bore?

 

[mcfred]

Re: bore curvature

Those are nice pictures, thanks for drawing them up! It clearly shows the two methods being discussed.

What I'm getting out of this thread is that while it is probably more technically accurate to align the chamber with the bore in the immediate vicinity of the chamber, it doesn't seem to be that critical.

One thing I don't understand is the "floating" reamer tools. Why go to all the trouble of indicating everything in just to let the reamer float? The reamer will naturally want to follow the bore, but it seems like you could help it by indicating things in and pushing the back end with a center.

 

[300sniper]

Re: bore curvature

Re: floating reamer holders, is your tail stock perfectly aligned everywhere on the bed? Does it stay perfectly aligned through the ram travel? I know the answer is no on my machine so I align the bore how I want it, single point prebore and use a floating holder.

 

[Al_Ski]

Re: bore curvature

The drawings are interseting though they are a over exaggeration/miss conception of an actual barrel...

Gun drills don't follow a specific path so the curviture wanders in different directions through the length of a barrel.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">One thing I don't understand is the "floating" reamer tools. Why go to all the trouble of indicating everything in just to let the reamer float? The reamer will naturally want to follow the bore, but it seems like you could help it by indicating things in and pushing the back end with a center. </div></div>

Reamers don't bend so following a curved path isn't a good idea and it isn't the reason for using floating reamers. Pre-boring a chamber eliminates the curve.

 

[Straight Shooter]

Re: bore curvature

The exageration is one I can spot with my borescope in about 5 seconds on a barrel chambered with that method.

I agree a chamber out of line doesn't seem to affect accuracy based on testimony from some pretty credible sources here and personal obersvation of factory barrels but why not get the bullet started as straight as possible if it's something we can control?

 

[300sniper]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Al_Ski</div><div class="ubbcode-body">The drawings are interseting though they are a over exaggeration/miss conception of an actual barrel...

Gun drills don't follow a specific path so the curviture wanders in different directions through the length of a barrel . </div></div>

The idea is the same regardless if the barrel has a linear curve or random. But yes, as originally stated, the drawings were a gross exaggeration for visualization.

 

[Al_Ski]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Al_Ski</div><div class="ubbcode-body">The drawings are interseting though they are a over exaggeration/miss conception of an actual barrel...

Gun drills don't follow a specific path so the curviture wanders in different directions through the length of a barrel . </div></div>

The idea is the same regardless if the barrel has a linear curve or random. But yes, as originally stated, the drawings were a gross exaggeration for visualization. </div></div>

Yup...

My point is that if you dial in the point of the bore where the throat will be generated and then an arbitrary point say 2" further into the bore those two exact points will be concentric to each other, the area in between those points will have runout in them. So which chambering process is better?

 

[DAVETOOLEY]

Re: bore curvature

I had a barrel indicated in yesterday and just for the heck of it I checked the run out from 2.75", the throat, to about .375" in from the breech end. I got TIR .001" That's 5 tenths in about 2.5". Go from my original 2.75" location and then use that same run out per inch and apply that to the location of the bushing approximately 1" ahead of the throat. It's a very very small number. Like .0002" per inch. I don't use bushings that fit that close thus my statement about Mother nature finding the center. Also the way I do it the breech end of the reamer aligns with the throat and bushing. Reamers don't flex much unless they are under an abnormal strain as in pushed with a misaligned center which to some degree they all are. They will align themselves stress free if given a chance.

Just side note here for those who don't know my background. I come from the short range benchrest world. Started in '78. Moved to ELR varmint hunting in the early 90's then on to 1K BR. My rifles have set over 30 world records for accuracy both at short and long range benchrest. I have set 4 myself. One still stands an NBRSA 1K yd. small group record shot with of all things flat base bullets. They have won many National Championships. There are different ways to skin this cat. I know you can check my work anyway you would like and I'm confident you won't find any flaws.

I'm out of here, got barrels that need plumbing.

 

[jrm850]

Re: bore curvature

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dave Tooley</div><div class="ubbcode-body">
Just side note here for those who don't know my background...
</div></div>

When I first joined this site and saw your name, I wondered if you were Dave Tooley's son.

 

[DAVETOOLEY]

Re: bore curvature

Now I'm not that damn old. Yet
Don't have time to get old. I was talking to a friend at the Shot Show and I said I don't know what's going to happen to me when I retire/slow down or whatever. He said I'll probably seize up. He's probably right.

 

[jrm850]

Re: bore curvature

Trust me, that was meant as a compliment. You have been very good at this for a long time. I knew who you were twenty+ years ago when I was just getting started.

I think it was either Bear Bryant or Bobby Bowden that said "there is only one big event left in life after retirement". I think working till I seize sounds like a good plan, I just wish I had the option to choose.