Chamber run out - may be of interest

[gbal]

no before and .0001 after

 

Thanks Mark,my bad.

 

Snag with tight neck examples,is that there can't be an accuracy/precision firing done out of the box,so there is no way of knowing if the out of the box at .0005 would have shot any different to how the prepped and fireformed .0001 brass do-any comparison would have to be confounded by different rifles.

A no neck turn rifle shot with "from the box brass" and also then shot with prepped from the same box brass might do it-someone must have done it.......and measured the targets....enough to get a reliable and valid conclusion...

 

Only the real engineers know fulwell that tolerance is also what we can tolerate- .001 (%) might make a difference in the real world,and it might not...statistics are great,but a 'statistically significant' difference is not neccessarily a 'meaningful/noticeable/do something about it difference. Nor is an apparently quite big difference always statistically significant......oops,sorry,I've retired from all that. Just be really nice if super skilled work was seen to be superior at the other terminal cutting edge (skin,paper). :-)

g

[silpig]

Some centre lathes clearly have better tolerances than others.

 

 

Under power, chambering speed - still sub 2/10ths (.2 ten thousandths of an inch) run out - thats with the bearings cold as I took the footage this (chilly) morning.

 

 

Ive seen videos from several other rifle smiths - Tooley, Paddy Dane, Mik Maksimovic, Jim Borden, Speedy Gonzalez, Gordy Gritters etc etc etc who also show zero or almost zero run out on chambers when set up with dial indicator at rear of chamber under load.

 

 

I don't think its unusual personally, its a tolerance standard I like to have and hold to wherever possible in all my builds.

 

 

Hope the link works as its my first posted video on U tube

 

 

 

Good stuff!

All I would say is that the dial indicator should really be presented to the work at a better angle - sat up like that it will only be showing the majority of any present runout - but not all! Possibly splitting hairs but when talking about things SO small you have to and of course hairs are considerably bigger than 0.0002".

[Big Al]

just realtered my figures in past posts as id added to many 0's

 

OK, that makes quite a bit of difference.

 

So out of the box Lapua will be running +/- 0.005" at best before neck turning?

[baldie]

Just realised whilst having a nice soak..

 

None of us have mentioned that the chamber runout is not relevant particularly, unless we are talking about it in relation to the bore. The conversation won't mean much to non machinists unless you realise this.

 

The two important points that can be easily measured are the rear of the chamber as in Andy's video's and the case neck area of the chamber. Ideally the leade is a better point, and the actual bore just in front of the leade, better still. This is difficult to read on a long fingered Verdict when the lathe is turned by hand, and impossible under power though.

 

All fascinating stuff and always something to learn every day. Only by sharing knowledge is progress made.

 

The important thing is people keep trying.

[techno_brat]

My chambers measure a similar runout of 0.0001 to 0.0002" , but are chambered , Outboard, i.e. the length of the barrel out of the chuck. I,ve chambered barrels between chucks on the same lathe and got the same figures. I don't believe them personally. I would,t run the lathe, warm, at chambering speeds for fear of buggering the instruments.

Hi Baldie, if you don't go through the headstock, how do you chamber your barrels? And do you use a floating holder too?

 

Jack

[baldie]

I chamber by both methods. Through the headstock on long barrels.

 

Short barrels are done by cutting a tenon at the muzzle, from the bore, then supporting the muzzle end in a revolving 3 point steady. Difficult to explain, simple in operation, and just as accurate as through the head, but easier and quicker to set up.

 

Floating reamer holder and a very long oil feed system. The Americans have always favoured this method for some reason.

 

Many ways to skin the cat, and each gunsmith has their own preferences .

[techno_brat]

I chamber by both methods. Through the headstock on long barrels.

 

Short barrels are done by cutting a tenon at the muzzle, from the bore, then supporting the muzzle end in a revolving 3 point steady. Difficult to explain, simple in operation, and just as accurate as through the head, but easier and quicker to set up.

 

Floating reamer holder and a very long oil feed system. The Americans have always favoured this method for some reason.

 

Many ways to skin the cat, and each gunsmith has their own preferences .

Sounds an interesting setup! I don't suppose you could post some picks? Obviously not in ronin's thread, maybe a new one? I don't wish to hi-jack threads, It's hard to visualise.

[Ronin]

Wow,

 

 

didn't think that the post would provoke such discussion.

 

 

Angle of indicator - the indicator has a tiny "ball" at the end of the stem, it was the only part touching the chamber, so I've no reason to doubt the readings shown - possibly some camera angle / eye trickery coming through too, as it looked fine when I set the indicator in place.

 

 

Run out - does it make a difference to accuracy…..?

 

 

Yes

 

 

How much?

 

 

No idea.

 

 

Imagine this though - a chamber that runs out is essentially oval, the more run out, the more oval the shape and the more out of alignment from the centre of the bore the more "cock eyed" the cartridge is in the chamber.

 

Fire the cartridge in a chamber thats well out and you have perfectly formed ovalised brass...

 

The bullet will also be slightly mis aligned to the bore within the leade

 

When the powder is ignited, 650000 psi pressure will have an effect of the misaligned chamber, brass and bullet.

 

 

If you don't believe me, then have a read of Harold Vaughns "Rifle Accuracy the Facts" who conducted numerous tests on what does and does not affect rifle accuracy when putting the things together.

 

 

Is the effect measurable?

 

Again, can't say…..

 

BUT

 

If I went to a chap and asked them to build me a rifle and they were not OCD about precision, their work ethic and standards, id walk away

 

 

My reamers have live pilots, I have pilots in .0001" increments in every calibre I work on (.224" through to .338")

 

The pilots are a slip fit in the bore and during chambering I check for fit of the pilot in case the barrel changes diameter - they sometimes do.

 

The pilot follows the bore, subsequently the reamer follows and will rarely deviate off course - how can it…therefore the throat / leade rarely has any run out. I have a long stem indicator, but have been told from several sources whom I respect and trust that measuring the rear of the chamber for run out is the better place to check (if using live, slip fit pilots)

 

 

Every little facet of putting together a rifle has an effect,

 

The bolt whose lugs don't have equal contact - causes the action to twist during the firing cycle

 

The bolt head that isn't square and true has the same effect

 

The slightly misaligned crown - causes uneven pressure on the bullet base on exit from the muzzle

 

The ovalised chamber - uneven / misaligned brass, misaligned bullet entry to throat and leade..

 

 

All stacks up to affect accuracy.

 

Does it affect accuracy in non "fitted neck" chambers?

 

No idea

 

 

Why do I do it this way - because I can and because I want to say hand on heart I couldn't make it any better to every one I build for.

 

 

The point I was and am trying to make is regardless of what rifle I work on, I try and put them together to Bench rest / F Class / Match standards.

 

 

If a jobs worth doing, do the best you can.

[1967spud]

Wow,

 

 

didn't think that the post would provoke such discussion.

 

 

Angle of indicator - the indicator has a tiny "ball" at the end of the stem, it was the only part touching the chamber, so I've no reason to doubt the readings shown - possibly some camera angle / eye trickery coming through too, as it looked fine when I set the indicator in place.

 

 

Run out - does it make a difference to accuracy…..?

 

 

Yes

 

 

How much?

 

 

No idea.

 

 

Imagine this though - a chamber that runs out is essentially oval, the more run out, the more oval the shape and the more out of alignment from the centre of the bore the more "cock eyed" the cartridge is in the chamber.

 

Fire the cartridge in a chamber thats well out and you have perfectly formed ovalised brass...

 

The bullet will also be slightly mis aligned to the bore within the leade

 

When the powder is ignited, 650000 psi pressure will have an effect of the misaligned chamber, brass and bullet.

 

 

If you don't believe me, then have a read of Harold Vaughns "Rifle Accuracy the Facts" who conducted numerous tests on what does and does not affect rifle accuracy when putting the things together.

 

 

Is the effect measurable?

 

Again, can't say…..

 

BUT

 

If I went to a chap and asked them to build me a rifle and they were not OCD about precision, their work ethic and standards, id walk away

 

 

My reamers have live pilots, I have pilots in .0001" increments in every calibre I work on (.224" through to .338")

 

The pilots are a slip fit in the bore and during chambering I check for fit of the pilot in case the barrel changes diameter - they sometimes do.

 

The pilot follows the bore, subsequently the reamer follows and will rarely deviate off course - how can it…therefore the throat / leade rarely has any run out. I have a long stem indicator, but have been told from several sources whom I respect and trust that measuring the rear of the chamber for run out is the better place to check (if using live, slip fit pilots)

 

 

Every little facet of putting together a rifle has an effect,

 

The bolt whose lugs don't have equal contact - causes the action to twist during the firing cycle

 

The bolt head that isn't square and true has the same effect

 

The slightly misaligned crown - causes uneven pressure on the bullet base on exit from the muzzle

 

The ovalised chamber - uneven / misaligned brass, misaligned bullet entry to throat and leade..

 

 

All stacks up to affect accuracy.

 

Does it affect accuracy in non "fitted neck" chambers?

 

No idea

 

 

Why do I do it this way - because I can and because I want to say hand on heart I couldn't make it any better to every one I build for.

 

 

The point I was and am trying to make is regardless of what rifle I work on, I try and put them together to Bench rest / F Class / Match standards.

 

 

If a jobs worth doing, do the best you can.

well put

[Offroad Gary]

Ok, that patter gets you the job next time I need one!

[silpig]

 

 

 

"Angle of indicator - the indicator has a tiny "ball" at the end of the stem, it was the only part touching the chamber, so I've no reason to doubt the readings shown - possibly some camera angle / eye trickery coming through too, as it looked fine when I set the indicator in place."

 

When using a lever type dial, the movement of the stylus should be set as close to perpendicular to the axis of the rotating part, as possible. This can only be achieved if the stylus is as close to parallel to the axis of the rotating part, as possible. If you set your stylus at 90 degrees to the job and touched it on (in the same way you would for a plunger type dial) you wouldn't see any movement registering on the clock because it couldn't even function like this! Move it over 5 degrees from that position and it might register some movement but not a fraction of what it should. Move it to 45 degrees (roughly where you appeared to have it) and as I said before, you'll probably see most of your runout, but definitely not all.

 

"Fist year apprentice stuff"

 

Please don't get me wrong, I'm not trying to pick holes! I barrel a few guns myself and really enjoy reading about other methods and setups, especially from fellow brits! I wish there was more of it!

 

Out of interest, what's your method of dialling in the bore - long reach indicator, range rod or other???

[Big Al]

Interesting stuff guys, keep it coming

[Ronin]

 

 

Out of interest, what's your method of dialling in the bore - long reach indicator, range rod or other???

 

 

Range rods with matched pilots for slip fit in the bore or Deltronic pin gauges (I've got both)

 

 

 

Whether any of what I do has a positive effect on accuracy, I can't say, though H Vaughan certainly believes it does in his authoritative book,,,

 

 

I know that most of the rifles I make certainly shoot "adequately" well.

 

The reason why I do it this way,,,, well thats the way I've been shown and world class rifle builders apparently also do the same.

 

 

 

I have no issues Ronin with you doing everything that you describe or your desire to get as close to perfection as you can - I can relate to that. I must say though if I wanted that level of precision I would not have been looking for it in a Warco machine, even if you have been lucky enough to find a decent one, Ive seen too many crap Chinese machines to put much faith in them.

 

 

 

 

I looked long and hard at several "light use" British made lathes before buying the lathe I've currently got (and owned the last 10 years)

 

Nothing wrong with it at all - "toolroom" quality and after all the purpose its used for is pretty light use.

 

If I were to change or add, i'd be buying a Nobilla refurbished Colchester Student 2500 or Master 3100

 

I know of several US "Benchrest" quality rifle smiths who use Southbend Heavy 10 lathes which are older than I am, yet they produce world class rifles using a a pretty basic machine..

[bradders]

 

 

Range rods with matched pilots for slip fit in the bore or Deltronic pin gauges (I've got both)

 

 

 

Whether any of what I do has a positive effect on accuracy, I can't say, though H Vaughan certainly believes it does in his authoritative book,,,

 

 

I know that most of the rifles I make certainly shoot "adequately" well.

 

The reason why I do it this way,,,, well thats the way I've been shown and world class rifle builders apparently also do the same.

 

 

 

 

 

I looked long and hard at several "light use" British made lathes before buying the lathe I've currently got (and owned the last 10 years)

 

Nothing wrong with it at all - "toolroom" quality and after all the purpose its used for is pretty light use.

 

If I were to change or add, i'd be buying a Nobilla refurbished Colchester Student 2500 or Master 3100

 

I know of several US "Benchrest" quality rifle smiths who use Southbend Heavy 10 lathes which are older than I am, yet they produce world class rifles using a a pretty basic machine..

It's not necessarily the machine, it's how you use it.

Lathe work for gun plumbing is nothing spectacular, after all most smiths buy an already profiled barrel blank, turn a tenon on one or both ends up to less than 1" long at the correct diameter, cut a decent thread then ream a chamber into it.

But if you take the care to clock it up and take care with all these steps the job is hardly going to be bad.

 

Is it beneficial? Probably.

But you always get guns that didn't have quite as much care taken over that can shoot better than ones that have had more care bestowed upon them.

 

As with everything, do the best you can possibly do

[Chris-NZ]

...

When the powder is ignited, 650000 psi pressure ...

 

 

 

 

Another one of those sneaky zeros has snuck in

[Ronin]

Dial Indicator placed at better angle / position as discussed in previous replies.

 

No real difference in results ……...

 

 

[gbal]

Well spotted,Chris. ITs unlikely even our 6.5 enthusiasts exceed 75,000psi ! :-)

 

A naive question:

 

I can see that a chamber that is nonconcentric with the bore is unlikely to start the bullets flight optimally;

But how does even cylindrical concentric chamber that is a little bit fat (few thou greater diameter) allow the cartridge to chamber easily,and when fired,does this now oversized cartridge not pose tightness in reloading dies? (the chamber having been cut too big,as it were-"botched ackley".

This does not seem to happen,so tolerances must be quite low,but met in chambering? Or are SAAMI chamber dimensions generous enough to accomodate several thou anyhow-I have kind of lost confidence with all these zeros flitting in and out,as to just where this is after the decimal point! If the tolerance is already greater by a decimal place,2 thiu say,is precision to the next decimal critical.

 

I admire those who understand all this,and especially can do it.High standards are admirable.Performance correlates would be reassuring. Are we talking about half an hour or half a day in meticulousness?

I'm not asking for professional secrets etc-I would not understand anyhow,as above will testify!!

 

Where are we on the asymptote plot of time v returns?

 

gbal

[John UK]

Dial Indicator placed at better angle / position as discussed in previous replies.

 

No real difference in results ……...

 

 

Hi ,what make is your lathe ?How old ?

Great thread guys.

[Ronin]

Lathe is a GH1330, I've owned it since 2006.

 

Its a good one

[John UK]

It seems a very good lathe.Class 4 bearing rating has.000098" max runout ...hard to thing colchester lathes have as much from new.

Class 2 bearings has.000047" max runout .

[nowler]

if using live pilot reamers, you will only have minimal chamber run-out if the hole the pilot is following is straight and the pilot is a nice close fit. a lot of the barrels i chambered were far from straight, dial it in at each end using interapid's on deltronic pins and spin it slowly and you'll see the bore through the middle of the barrel moving up and down... so cutting the entire chamber by live pilot method and using a suitable reamer holder and you have to expect run-out in the chamber.

 

some guys try and clock this in so the bullet exit is on the rise for positive compensation and more consistency once the barrel starts to heat up. it's easier to adjust elevation than try and work out if it's the barrel or the wind that's pushing you sideways.

 

i wouldn't care if the rear of the chamber ran out as much as 3 or 4 thou. this is not uncommon in a well chambered barrel. the important bit is what is happening at the other end.

[Ronin]

As ever, wise words D.

 

The machine is performing well.

 

What happens at the other end…..thats pretty much governed by the steerer, assuming the crown is sound

[nowler]

alright big fella? i hope you are well!

 

by the other end i meant the throat but you're also correct....

 

i'm flogging my new .308 ftr rifle if you know anyone who's in the market for one. it's in the classifieds just now

 

keep up the good work by the way, those interapid's are the nuts eh?

[Ronin]

Hey, I thought you were coming back to kick ass,,

 

Ive two Rimrocks for sale - come back to Open…...

[bradders]

My new GH 1330 arrived a couple of days ago, don't know why I didn't do it years ago

Zero runout on a 22" turn and the DRO adds a completely new dimension

 

I'm a happy bunny

 

For all the Naysayers, these are sold in the Good Ol' US of A under the Grizzly name, and plenty of their top gun plumbers use them

 

Mine

Some time later