chamber roundness

I must be a glutton for punishment....:rolleyes:

#1- the easiest way I know to measure your indexing is to make up a dummy barrel stub. For ME this is easy because I've always got take-off barrels laying around. I just use one of these. I can't see how/why anyone would "avoid the issue." Another is to make an action dummy, or use another action if you've got access to it. Bottoming out the chamber by hand makes it easier......for me..... some may take issue with this :) and that's OK too.

#2- While we "may" all agree that indexing to centerline is important for tracking, (I don't) I've got two brand-new barrels done using Jerry's method.... barrels done by someone Jerry knows well and would trust with his own stuff..... which shoot clear out of the scope adjustment at 100yds. To the SIDE.

I can't for the life of me see as how anyone thinks that aligning the front hole with the back hole somehow cancels the curve, my own luck has been about 70-30 with long barrels. And my experience base is wicked thin and narrow but I've got three barrels that are significantly off centerline. I will agree that aligning the holes takes some of it away.

For short little BR barrels I'm @ 100%, I can screw barrels off and on and just clik over 3-5" to my bullet hole . Straight barrels? luck? dunno.

al
 
alinwa said:
I must be a glutton for punishment....:rolleyes:

#2- While we "may" all agree that indexing to centerline is important for tracking, (I don't) I've got two brand-new barrels done using Jerry's method.... barrels done by someone Jerry knows well and would trust with his own stuff..... which shoot clear out of the scope adjustment at 100yds. To the SIDE.


al
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I don't know who this Jerry knows and would trust but I have never even seen a barrel done by a good benchrest gunsmith that would shoot out the side beyond scope adjustment [ at 100 yards:confused: I would consider that a real crummy fitting job. I'd bet any amount of money you care to bet that if the chamber neck and bore exit were lined up when the tennon shooulder was cut the point of impact will not be off over just a couple or three inches. Who do you think you are fooling AL:confused:
 
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Mark2 said:
I don't know who this Jerry knows and would trust but I have never even seen a barrel done by a good benchrest gunsmith that would shoot out the side beyond scope adjustment [ at 100 yards:confused: I would consider that a real crummy fitting job. I'd bet any amount of money you care to bet that if the chamber neck and bore exit were lined up when the tennon shooulder was cut the point of impact will not be off over just a coulle or three inches. Who do you think you are fooling AL:confused:
Click to expand...

I'll look into this more before I go any further....... my figures show that for this to happen we need almost a tenth inch of curvature in the bore. Nevertheless, I just had to bed a scope over to center it up because it DID impact clear in the corner of the adjustment after switching the rings end for end (gently) to assure that they were not buggered, and a new BAT with a 30-something inch bbl is also impacting clear at the extreme edge of adjustment. (I only note that it's a BAT because I think we're in agreement that BAT's are straight actions)

In both cases scopes are/were spun and centered in the rings.

I must further note that in both cases the actual poi is 12"-14" off of center because in the one rifle it's both low and right which cuts available adjustment of scope in half and on the other there's a 20moa base installed so the scope starts off in the bottom of the trough, again, only 14-16" of adjustment available.

Let me rephrase this...... I've got two barrels which are indexed such that they impact 12"-14" to the side.

I see your point and need to get to the bottom of it before asserting that it's because of a crooked bore.

al
 
alinwa said:
I'll look into this more before I go any further....... (I only note that it's a BAT because I think we're in agreement that BAT's are straight actions)

In both cases scopes are/were spun and centered in the rings.

I must further note that in both cases the actual poi is 12"-14" off of center because in the one rifle it's both low and right which cuts available adjustment of scope in half and on the other there's a 20moa base installed so the scope starts off in the bottom of the trough, again, only 14-16" of adjustment available.

Let me rephrase this...... I've got two barrels which are indexed such that they impact 12"-14" to the side.

I see your point and need to get to the bottom of it before asserting that it's because of a crooked bore.

al
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Since you are the one who brought BAT up, I know for fact BAT has recently gotten at least some their rings made outside. I also know for fact that one set I put on had to be shimmed up 0.010 to put both bores on the same centerline. Otherwise the scope tube would have had to be bent. We found this out that something was bad wrong when I started the ring lapping. The bores of the rings were way out on the bottom edge. On another set, recently, the base screw holes were off on the center to center distance. I called BAT and they admitted they were having ring problems. BAT has a good reputation I just hope they don't have Toyota making parts for them.



And still no one has answered the question Ken ask above about indexing. It is apparent your gunsmith doesn't know either.
 
Mark2 said:
Since you are the one who brought BAT up, I know for fact BAT has recently gotten at least some their rings made outside. I also know for fact that one set I put on had to be shimmed up 0.010 to put both bores on the same centerline. Otherwise the scope tube would have had to be bent. We found this out that something was bad wrong when I started the ring lapping. The bores of the rings were way out on the bottom edge. On another set, recently, the base screw holes were off on the center to center distance. I called BAT and they admitted they were having ring problems. BAT has a good reputation I just hope they don't have Toyota making parts for them.



And still no one has answered the question Ken ask above about indexing. It is apparent your gunsmith doesn't know either.
Click to expand...

Interesting info about the possibility of BAT's being set up crookedy. I assumed that the critical surfaces and penetrations were machined from one setup like a Borden. I do notice tapped holes..... in my case poorly tapped holes.....

Regarding the method.... I've used three gunsmith's through the years, none of them using Gordy's method. I recently bought a lathe and am also doing some of my own work. I'm the one playing with the range rod. A Kiff or "Grizzly" rod. Indexing for me is still kinda' trial and error but that's because I suck, no indictment on the method.

al
 
It is not hard to index the barrel. Doing it the way Al and Gordy set up their barrels the muzzle will flop up and down. Put an indicator on the flopping end and mark the high point. I assume the low point will be 180 deg. from the high.
For the breech end make a barrel stub or take an old barrel and screw it in the receiver and mark the top. I have a tool that will screw onto either your barrel stub or an old barrel.
DSC02292.jpg

Make a reference mark on the tool and screw it on the new barrel. Machine the shoulder until the reference mark is on top and matches the mark on the muzzle. I hope you understand what I am saying. As stated before, it could make it a real problem getting on paper chambering this way. I haven't checked it, but Al I think a tenth of an inch at the muzzle could be in the next county at 600 yds.
Butch
 
My next stupid question, how much extra time is it going to take to get the barrel indexed up (up probably is best??) and the chamber headspace properly set? On the conventional method if the headspace is too much, like 005" just take 005" off the shoulder. If the headspace is too little like 005 just run the reamer in 005 deeper. On the range rod method say the headspace is too deep by 005, then what? another revolution on the index?
 
Mark2 said:
My next stupid question, how much extra time is it going to take to get the barrel indexed up (up probably is best??) and the chamber headspace properly set? On the conventional method if the headspace is too much, like 005" just take 005" off the shoulder. If the headspace is too little like 005 just run the reamer in 005 deeper. On the range rod method say the headspace is too deep by 005, then what? another revolution on the index?
Click to expand...

well, it takes me DAYS!!! :p (evenings) and I sometimes just set on a chair with a cuppa' cawffee and a smoke and stare at the stuff. I keep notebooks on every flat surface and sometimes have to collate three sets of notes to find out where I left off. There's another notebook on my nightstand.....

I guess this is kinda' no different than trying to save the lettering...... fact is, if you go to far you're just screwed ;) You go another whole turn, or if you're not gonna take it off you "could" shim it (I din't really say that :D) or if it's got a recoil lug, fix it with that. Or cut down a recoil lug or make a realio-trulio spacer as long as your bf-to-barrel doesn't get too long..... don't wanna make a M70 Win out of it! ;) Ruptured cases is scarey.

I'm kinda' getting out of my personal comfort zone here. I went to gunsmithing school in 1981-82........ I learned enough to know who to hire to do the Good Stuff, and I now do this for fun. I'll be good one of these days, but right now??? I'm still breaking in and trying to learn GOOD HABITS this go-round. There's guys here (Jerry Sharrett included) who have the tooling, experience and can do stuff with setup that I'm completely incapable of with my little lathe. I can't really even "feel" my lathe yet. Every day's a new day :eek:

IMO indexing up is proper, and getting on paper isn't hard at all, You will hit high and near-on centerline. It's a whole hang'ofalot easier than searching around the target backer randomly like I've done recently with a brand new Lilja and PacNor having no idea where to look for a bullet. And finding them off in neverland......

and BTW I have a Time gun with 7 barrels done by two different people..... it's got .22BR and 6BR barrels, 6PPC, .243AI and even a .308 barrel and they'll all screw in and out and print within 4-5" @ 100yds. I'm perty used to shooting once and dialing over and going straight to target. But I've recently gotten two which did NOT come in close. On of them, a 25" .270 Lilja, was turned and deeply fluted by Lilja. I kinda' expected it to walk and it did evidently. The other is a long PacNor in a 32" Palma, again, NOT your typical target bbl.... but they're both way wild.


BTW Butch, I shot your Shadetree Tuner for effect for the first time last Sat and the rifle flatout tabletopped at 600..... less than an inch of vert with a foot of hor..... until the headwind kicked up. I got away with two plaques for Light Gun, Small Agg and High Score against some good shooters....... mainly because I drew 1st relay. ;) I'm starting to think maybe steenkin' Billy Copelin can shoot better than me :D and this guy named Dell Martin taught us ALL a lesson in leavin'......

al
 
Well, here goes a trial method for indexing

I'm not an accomplished machinist but with some patient coaching from Jackie Schmidt and Jerry Sharrett, I've been able to turn out a few pretty good barrel jobs---but only by indicating at the muzzle and throat.

I like the idea of Butch's neat tool but don't have one and would have to use my own method.

I've never done this and can't claim success with it---feel free to tear it apart.

I'll assume a Rem action-----16 TPI, .0625" pitch and a barrel diameter of
1.2", circumference of 3.14159 X 1.2 or 3.770 ". My understanding of this is that a complete revolution of the barrel inward will produce .0625" of inward movement.

1) Start by turning and threading the tenon per whatever numbers you'd use without considering indexing.

2) Screw the action on the barrel and tighten a bit-----while still in the lathe.

3) Place a strip of masking tape around the barrel, slightly ahead of the action face---and make a mark on the tape at the top center of the action face

4) While indicating at the muzzle, turn the chuck to find the highest point indicated.

5) While in this chuck position, make another mark on the tape at the top center of the barrel, just ahead of the action face-----might help to use an indicator to find this high spot on the barrel.

6) Measure the distance between these marks----might be better to remove the tape and stick it down on a flat surface to make the measurement easier.

7) If the action tightens up with its top center on the left side of the barrel, the measurement on the tape is used as is to calculate the amount the tenon shoulder should be moved forward.

8) If the action center tightens up on the right side of the barrel, you'll have to subtract your measured amount from the barrel circumference to get the number to calculate the amount of tenon shoulder movement.

9) To calculate the amound of tenon shoulder movement:

The appropriate number from 7) or 8) above is divided by the barrel circumference and multiplied by the thread pitch.

10) Example: With the action center to the left of the barrel and a measurment on the tape of .9", the tenon shoulder movement would be:
(.9 / 3.770) X .0625 or .015"

11) Example: With the action center to the right of the barrel and a measurment on the tape of .9", the tenon shoulder movement would be:
(3.770 - .9) / 3.770 X .0625 or .048"

Without the specialized equipment and with no other recommendations, I'd try this method. It would be much easier to do this than to push all this across the keyboard. Butch's method sounds a lot easier.

Feel free to tear into it.

A. Weldy
 
well, with all this being said and written about range rods and indexing it seems like a bunch more trouble than the conventional method. does anyone have proof that the range rod chambered barrel will shoot any better? it looks like to me anyway more like trying to correct a deliberately induced mistake.
 
Butch Lambert said:
Mark,
Do your indexing before headspacing.
Butch
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First, thanks Butch. But, Butch, just but, what happens if you go a few thou too far with the reamer? Another turn then then try to pick up the already threaded tenon? I know I've gone a few thou too deep and had to shave a few thou off the shoulder, then take the same amount off the end.
 
A. Weldy.

Your method is good, however, I would use a slightly different method to clock the measurement.

I would take an automotive degree wheel, slightly larger than the chuck, cut it in half at the 0.0 degree position, then situate it between headstock and chuck.
With action attached, level the action.
Using a pencil taped to the chuck as a pointer, pointed at the 3 0’clock 0.0, indicate the degrees of chuck rotation necessary, rotated ccw as viewed from the t.s., to bring the barrel within the desired coincidence. If you need more than 180 degrees rotation, again tape a pointer to the 0.0 degree mark on the degree wheel, rotate, and add this amount to the 180 degrees.
Calculate.
Degrees of rotation / 360 x T.P. = shoulder cut needed.
ex.: 200deg. / 360 x 0.0625” = 0.034”

Longshooter
 
Longshooter

I understand your method but am not familiar with the automotive wheel.

I'm not sure that I have a good way to directly measure rotation in degrees. Linear measurement is more practical for me.

Either way, you have to determine a percentage of a full rotation as a multiplier of the the thread pitch.

I'd be surprised if I ever indexed a barrel. The method Jackie and Jerry finally pounded into my thick head works very well for me. I like it.

A. Weldy
 
Range Rods

While I do not personally use this method, it is a satisfactory method of getting two points in a barrel running true.

Gordy is also a pretty good teacher, he has a logical way of putting things to where the lay person can understand what and why he is doing what he is doing...........jackie
 
jackie schmidt said:
While I do not personally use this method, it is a satisfactory method of getting two points in a barrel running true.

Gordy is also a pretty good teacher, he has a logical way of putting things to where the lay person can understand what and why he is doing what he is doing...........jackie
Click to expand...

does he have a video showing how to index? I still don't see a good method explained so far. I think there IS agreement that the barrel must be indexed UP, but how to do it??:confused::confused: and it there proof that a range rod alignment produces a more accurate barrel?
 
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I know several guys who have lathes that do not allow a external spider, small spindle bore, long headstock, etc. Could the range rod method be used in a steadyrest setup on a barrel that has quite a bit of curve? I've seen several lately where the barrel muzzle would wobble about 0.1".
 
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