OzFclass

Hi everyone , can anyone tell me what it does , how it does it and have they had any noticeable success with it? Or is it just another time wasting process that makes us feel better ? Eg makes up for lack of skill and confidence!

http://www.bulletdoctor.com/

Regards Graham Sells.

Well, this is a topic with many conflicting views that I have followed off and on for the last 15 or so years. There has been a really worthwhile thread on this topic on benchrest central this year, again with many divided opinions on the subject. Check out http://warningwww.benchrest.com/showthr ... 8b106d66e6 for 11 pages of discussion, though I dont believe you will find many definitive answers on the thread (at least not from anyone that actually knows what they are talking about).

I think it is fair to say that people remain unclear on WHAT the Vern Juenke is actually measuring (and I am not going to give any opinion on that subject).

However there appears to be enough empirical evidence from use by good shooters in various shooting disciplines to suggest that sorting bullets on the Vern Juenke has helped them to improve their results in both long range and short range competition.

And just for the record, the link you posted is not an actual Vern Juenke - it is a modern clone which reverse-engineers Vern Juenke, and outwardly looks the same as a Vern Juenke.

I looked into these a while ago. It doesn't do what I expected. As I understand it, this machine measures the thickness of the case at points around the circumference of the projectile. ie it is telling you how central/concentric the led core is. If the lead is off to one side the bullet would be out of balance. That said, from long distant memories of a spinning top and bits of plasticine. It doesn't make a jot of difference as long as the bullet is spinning fast enough. Once it slows down however, things get a bit exciting (I was young and easily impressed).

I think more could be achieved, with directly related results, by simply spinning the bullet and measuring the variations (miniature tire balancing). I don't think you would actually need to measure anything, spin the bullet up and if it doesn't throw itself out of the rig, she's all good.

plumbs7 wrote:Hi everyone , can anyone tell me what it does , how it does it and have they had any noticeable success with it? Or is it just another time wasting process that makes us feel better ? Eg makes up for lack of skill and confidence!

http://www.bulletdoctor.com/

Regards Graham Sells.

Graham

Ask me when we next meet. I have used extensively in the past.
The original machine is not made anymore.

Cam

Concentricity of the jacket and wall thickness as far as I can establish.

The signal generated by the sensor is disturbed by the jacket material as it is rotated. Regardless of whether the signal generated is ultrasonic, eddy-current or radar!

The reason it can't detect a void in the lead core is because a void doesn't necessarily cause the bullet to be swagged eccentrically. The sensor is not generating a a signal to a finite point, possibly a radiused plane but most likely a radiused area. This would be adjust by the dial setting?

When the bullet is rotated on the fixed ball bearings, there are three main conditions that can cause the signal measurement to fluctuate (and permutations thereof), that I can think of. Firstly the jacketed bullet does not rotate concentric to the axis points between the two fixed bearing points and the jacket wall thickness is concentric. You have a banana, not a bullet.

Secondly the bullet spins concentric to the axis created by the two fixed bearing points, but the bullet is eccentric between the two points. You have a cam shaft or mono-pump shaft, not a bullet.

Thirdly the bullet spins concentric to the axis created by the two fixed points, but the jacket wall changes in thickness between the two fixed bearing points. You have an accordion, not a bullet

So once-upon-a-time. ...considering the 2nd condition, the two fixed points are concentric, but you have something that looks like a cam shaft in between. If the cam shaft effect was measurable give the sensitivity of the ICC unit, but still minute and repeated frequently enough over the bullets bearing surface; I would surmise it's possible to get a poor ICC dispersion reading but still have a BR accurate bullet.

The question is then how do you know which condition you are getting...and why is the shooter I gave all my ICC 'dud' projectiles to still winning matches with them when I told him they were just barrel burners.

Think of it as the bullet already being scared with rifling marks. An accurate bullet had just been abused by rifling marks as deep as 0.004" travelling down the bore at 3000 fps. If this hasn't happened in the first 2" or at least before for bullet leaves the muzzle you're in trouble. Regardless of how soft the core material is, that gilding metal jacket is physically going to thin and wear across those rifling lines from friction.

That's all right, some tool & die maker just spent weeks of their life making sure the deep drawn jackets measured less than 0.0003" TIR across the entire batch; and there you go driving a nice set of helical cuts/gouges up to x10 deeper through their handy-work.

The evil scenario is where the jacket thinning follows a low frequency cam effect between the fixed bearing points. So it appears there is no change in jacket wall thickness as the cam lobe passes the sensor and the bullet still appears to be concentric between the fixed points. Again the ICC non-contact sensor can't physically grab the bullet and jacket and give a displacement in mm's it's purely measuring a signal change.

So like every fairy-tale has a moral - if you can control the 'error' and make it 'repeatable' you should expect that same result.

Somebody who measures TIR on thin walled tubes between two fixed points would probably be able to explain limitations of various concentricity measuring devices.

Cameron Mc wrote:

plumbs7 wrote:Hi everyone , can anyone tell me what it does , how it does it and have they had any noticeable success with it? Or is it just another time wasting process that makes us feel better ? Eg makes up for lack of skill and confidence!

http://www.bulletdoctor.com/

Regards Graham Sells.

Graham

Ask me when we next meet. I have used extensively in the past.
The original machine is not made anymore.

Cam

Hi Cam , sounds good as I'm struggling to get my head around it . Hope to catch up soon . Just having a little break at the moment!
Ps Dave is very keen to get back to the range !

Aaron I greatly appreciate ur comments . It's way above my head !

Still ... Has anyone had success other than Cam . Or heard of anyone had a win that it was worthwhile doing???? It would be very time consuming !

Graham, I honestly would not be concerned with Juenke's
I have found the good name projectiles are very consistant compared to some years ago. I believe competition in the market place has been a big driver here. Years back only a couple of big name players dominated then started to rely on reputation until these other companies upped their game. This has been all good news for us.
I am talking about long range projectiles here. Custom made short range BR projectiles have been around for many years.

Cam

I found this diagram today describing different types of runout and thought it goes a long way to explaining some of detail in my previous post - scroll down to unclenick's post #15 for the diagram http://www.shootersforum.com/handloading-procedures-practices/90496-basic-runout-question.html

Thanks Aaron, have u used yours yet? And have u had any notable improvements?
Regards Graham.
Ps be great to meet ya in person one day!

G'day all,
coming from an engineering background, the simplest way to measure your bullet run-out and consistency is to spin them up by shooting them.

If they shoot to acceptable levels = good. If not = bad

When all the mechanical errors are controlled or controlled to become "balanced" in a "good way" your will get the performance.

It's a bit like borescopes, everyone one can see things in their bore that scares them, but if the barrel shoots to acceptable levels of accuracy, get on with the shooting and ignore the observed (perceived) defects. On paper, they become meaningless IF the rifle is performing as expected.

It's just another thing that you worry about and you can't control. And it is probably the same for everyone's equipment. In fact a comprehensive equipment list of the top 10 shooters from OPM's is much more valuable information, than measuring/viewing something you cant properly measure, analyse or comprehend.

This simply does your head in worrying about things of no consequence. Which is the last thing you need on the mound in an OPM.

Better still invest the money for a Juenke in quality barrels, a scope, bullets or improved reloading techniques and processes and you probably can measure the improvements on target almost immediately!

Food for thought anyway

Cheerio Ned

plumbs7 wrote:Thanks Aaron, have u used yours yet? And have u had any notable improvements?
Regards Graham.
Ps be great to meet ya in person one day!

Never owned one myself, but I've had a few samples run through a couple of Junke's now.

Following some discussions with Junke owners regarding results, I'm inclined to agree with Cam.

In terms of a concentricity and TIR gauge they are relatively good value compared to other options in the marketplace. As a device for the average target shooter you are looking a 2-3 barrel commitment$$$$...and a lot more time (hh:mm) at the reloading bench because you need to measure every single projectile you intend to score with. Essentially the quality of LR projectiles has increased significantly that you might be lucky to reject 5/100 based on their Junke results alone. That doesn't mean to say you might not have rejected them sooner during a quicker earlier QA process anyway.

The unit seems to be able to identify heavy handed tipping, but non-concentric subtle tipping isn't enough to disturb the point bearing on the ogive to give a result (deviations). In fact the unit will read dead zero leaving you to think you have the perfect projectile, but not quite apparently. This is just an inherent limitation of the unit.

If a club was to buy a unit for it's members, I could see them being able to run a few samples from members batches of projectiles, just to make sure they got what they paid for and share the cost a unit that way.

If you run a lower quality projectile because that's all you can afford, or no other available options and you're prepared to put in the time, then I think the improvements would be significant. The problem is that cheap projectiles become relatively expensive if you designate 30% as barrel foulers, unless you know someone prepared to pay for them.

If you do come across a cheap Junke going for less than the cost a barrel, then you're left wondering if the unit is working properly and what happens if it needs repair???

They are still a great piece of engineering and a well looked after unit will always hold it's value if not appreciate. A Junke is bit like a heirloom, you don't own one so much as you're entrusted with it's safekeeping until you pass it onto the next accuracy nut.

I'm actually planning to do a few ranges this year, it would great to put a few usernames to faces, all be it they will have to suffer the unedited version of myself. Was even thinking about a demonstration one afternoon at Belmont on swaging for those that have thought about giving it a go?

ned kelly wrote:
This simply does your head in worrying about things of no consequence. Which is the last thing you need on the mound in an OPM.


Cheerio Ned

It's almost criminal how the shooting industry works at times.

I'm sure there are a few shooters around, that if you told them there was a 1 x inner 4 in the box of 500 and the rest were all perfect, they wouldn't sleep let alone make up to the mound before they found the defective unit...if it ever existed.

Well, on the weekend at 500 yds with quality lap brass and berger projectiles I managed a 85.6 15 count . Not too shabby !
I offered a young tr shooter ago at scoped rifle and he jumped at the chance ! I had some real crappy hornady steel match factory rounds , you know just to give him a feel! Now these rounds I've seen 50 Fps spread! So I thought he wouldn't do all that well hey!
Wrong ! He was on his way to an 88.4 until the last fee shots and dropped a 4 and another 5 to just let me beat him at 85.4! Why do I bother reloading!

This tells me that Remington is quite in tune !

I agree with Ned! G

Graham and Aaron, a long time ago I bought one of the original Verne Juenke machines and still have it but it is not used much. It was used to make sure that barrels being tested were using the best components for comparative results. It was not used for competition because the target size then accommodated the ammunition being used in full bore competition.

As Aaron has rightly indicated there are a lot of variables in the reading and some can counter each other. What I can say, and Fergus has brought to your attention another site discussing its merits at length, that the machine indicates a net (summary) of factors which could change bullet concentricity possibly core position (sideways, fore or aft), jacket thickness or lube etc. through an eddy current circuit that fades or increases as you spin the bullet on the machine. So the machine does not measure a specific factor. Although bigger diameter bullets do not fluctuate as much as smaller diameter bullets, I’m thinking the centre of mass which I am interested in, is further away from the machine sensor and not the jacket which most others seem to be interested in. This observation may also link with the ballistic role radial length has got to do with bullet gyroscopic stability as well as the correct balance with the centre of mass with centre of pressure for aerodynamic stability.

Its probably like a helicopter doing an electrical survey in mineral prospecting hot spots which can be mapped. But the miners always have to dig to find the gold as they can’t be sure of the exact location or what the anomalies really are on the map.

The general theme of comments was the Juenke machine did not matter for short range benchrest with flat based bullets (except if the jacket was out significantly, see below)) but was beneficial for 1000 yards. Perhaps the flat based bullets are easier to make and the boat tail throws up a few more anomalies. Aaron might comment. But I’m thinking the subtle difference could lie more with the centre of pressure and centre of mass. If you combine jacket or core imbalance as well as core position you will have greater dispersion at long range as well as the fact boat tails are designed to minimise long range drag.

Quote from Fergus’s site: “The following is average data based on the average lot of bullet jackets that the custom bullet makers can buy. 80 % of the finished bullets will run 5 or less deviation units (Hummer bullets). 15% will run 5 to 10 D.U. (still good bullets). 5% could run 10 to 15 D.U. (average bullets). Anything over 15 D.U. should be used for fire forming, fouling shots, pressure testing, and chronographing. There may not be many of these, but they could cause those small fliers that we all shoot once in a while. Don’t shoot these on match day. Give them to your worst friend!”

Is that what you did Aaron?

A tight throat and bore using the Obermyer theory, and jammed bullets tends to rework the bullet and so may explain why your friend is getting good results.

Something I have talked about before is a variable boat tail angle between projectiles which I once tried to measure with a shadowgraph, so critical to drag, velocity decay and stability at long range. Would you believe a poster on the site Fergus mentioned, positions his projectile on the Juenke machine with one of the bearings touching on the mid section of the boat tail? Interesting.

My current thinking is that the investment in the machine is not worth it because the best manufacturers supply bullets which are so well made. In my case, and owning a machine, I still have a lot of poorer quality projectiles on hand I want to use up having bought in bulk in the past when we could not get supply, (and who knows where world events and our dollar will go now), the Juenke machine will sort the wheat from the chaff to give me projectiles equal to the best bullets for long range. If you get a copy of Harold Vaughn’s book, Rifle Accuracy Facts, he shows you how to make two different bullet balancing rigs to test them. One floats the pill on an air cushion; the other suspends the pill between wires. Any hands on person can make the latter. David.