TargetTalk

My apologies Mark, you clearly know what you're talking about.

While I'm waiting for my starik tube to turn up I thought I'd experiment with adding wheel weights to my tube to bring it up to the same 220g total weight that Guy uses. I popped down to Bisley last night for a quick 60 shot match and the results............598/624.7 44x!!!! Absolutely smashed my old pb of 592 (and bisley pb of 585). So there would appear to be something to gain with weight at the end of the barrel!

The two nine's were the first shot after putting the rifle down for a break half way, and the second a 9.9 as the light levels fell. Looking forward to receiving guys tuner now.

Bryan

Hi Bryan:

So jealous that you have access to the Bisley range! I was there in 2009 and was in awe - what a beautiful and functional range.

We will be there next year for the Roberts Team and your Nationals - I am so looking forward to it. This will be a very long winter / off-season for sure.

I am not sure if you ever mentioned any details about your rifle in prior posts, if you don't mind me asking, could you please give me some detail (just curious).

Thanks,

kev

Kev, I'm very lucky Bisley is right on my doorstep. In fact I have to drive past Bisley to get to my club. PM me nearer the time of your visit and if I'm around (might be on holiday in August) I'll buy you a drink.

The rifle is an old 1813 that I bought three years ago when I started shooting and was rebarreled this year with a True Flite barrel (by Robert Nibbs), it's also now in a precise stock. In fact the only original part that remains is the action. I originally wanted to fit a benchmark barrel however after waiting over a year for the UK importer to get one I gave up and bought the true flite as they were in stock. It's had 3000 rounds through it now and seems to be improving.

cheers
Bryan

Just as an update, if anyone's interested.

Guy's tube has arrived and I've finally had chance to test it in a vice at Bisley.

I have two photos of the group size for 10 shots of Midas+ shot from a vice at 50m, without and with the turner.

So obviously there's a significant improvement with the tuner, this group was probably the best group size and the weight wasn't moved from the 0 position. I then wasted about 500 rds testing at different positions and things only really got worse, I didn't seem to find a few sweet spots that other people report. But I'll revisit again later, if I'm going to be competitive next year I'll need tighter groups than that!

Another point is that this same batch of Midas has tested better in the past, however that was when the barrel was new with less than a 1000rds through it and now it's upto about 4000 so has probably changed as its bedded in and isn't really 'matched' anymore.

Still work in progress but it would initially appear a worthwhile purchase.

Bryan,
I don't know which kind of vice you have used,but if it's a solid vice which doesn't recoil,tuning will do nothing!
In order to tune the rifle for positive compensation,you need to use a bench which recoils,or shoot from the shoulder,or sand bag...
Guy.

Thanks for chipping in Guy.

The vice was just a clamp, with no recoil feature. I had missed that bit in the instuctions on your website. And that does match with my inability to tune it. Why do you say a fixed vice wouldn't work?

I also dont understand why this would make any differance if the PRX theory was present, even Dr Kolbe's test ring didn't have any recoil feature, and therefore in my mind just confirms PRX doesn't exist. PRX after all was based on the movement of air in a tube with one end closed, such as a musical instrument. In a flute for example the particular musical note is acheived by vibrating the air, not vibrating the flute itself. On the only way to really test this idea would be to make a tube that is completely out of phase (but still the same weight) and compare back to back. I'd put money on the short tube still working!

I am converted, from the results above, that your tube works. I just believe that it is the increased mass that reduce's the muzzle sign wave vibration pattern to give the results, rather than PRX.

Bryan

Bryan,
In order to get positive compensation,you need the rifle to recoil.
I'm sure PRX works,because I have tested it.
I think that it will be better if Tony will answer you about PRX...
Dr Kolbe's rig can recoil. I have posted the pictures in another thread here.
Guy.

Bryan,

to elaborate on Guy's reply, I think Geoff Kolbe's rig allowed the barrel/action to pivot upwards.

Guy,

am I right in thinking a fixed vice would channel vibration back into the barrel?

Tim,
I'm guessing you mean a test jig like http://tec-hro.de/schiesssport/en/rifle ... bench.html

Guy,
You've obviously done a lot of testing with your product, I'd be interested to know the physics you think is at play for the tuner not to work in a fixed rest.

Peter

To have more understanding on the subject, take a look at:
varminal.com
For your questiones:
http://varmintal.com/a22lr.htm
Guy.

Thanks Guy, I'm aware of VarmintAl's analysis, and the software he used. What isn't addressed and what I haven't seen is an explanation to why the tuner will not work if the action is in a solid fixture.

Peter,
I'm sure the barrel vibration are different when Shooting from a solid vice compared to Shooting from the shoulder. The recoil makes the barrel oscilationes bigger, allowing positive compensation.
Guy.

Thanks for your reply Guy.

Hi All

When I first came up with PRX, it was primarily for the Benchrest crowd. The most common tuner used is a Harrels tuner. There are several associated weights and tubes that affix to the end of the tuner. What this all has in common is that entire set up can be moved in and out. As little as .025" of movement has a direct impact on grouping and precision. Adjusting the length for PRX for a given barrel is straight forward.

The Starik Carbon Tube works at two levels. PRX tunes to the length of the barrel, meaning that it will shoot different speeds accurately, but to different POI's. The separate adjustable weight affects the timing of the mechanical vibrations of the barrel, therefore allowing for positive compensation. It is important to note that for this to happen you need two different speed lots that independently group well.

I would be interested, Bryan. in where the rifle was clamped (barrel, stock, action, etc). I have recently worked with a set up where the barrel is clamped in the stock and PRX worked the same as any other set up.

Your comparison of the flute is rather spot on. Of note, though, is that the flute must be initially tuned before it can lay the correct notes. A small change in length can make the difference between a good clear note, and a note that is kin to scraping fingernails against a chalkboard.

I have tuned using effective tube lengths as short as 1" and as long as 15".

I will do my best to answer any other questions you may have.

Have a good nite

Tony Purdy
The Purdy Prescription (PRX)
Does your rifle shoot "Purdy Good?"

Hi Tony,
This part of your post has caught my attention

PRX2500 wrote: PRX tunes to the length of the barrel, meaning that it will shoot different speeds accurately, but to different POI's. The separate adjustable weight affects the timing of the mechanical vibrations of the barrel, therefore allowing for positive compensation.

If I understand this correctly, a PRX tune will reduce the group size but a fast bullet will still go high and vise versa.

If this is the case then am I correct in saying that a PRX tune is optimising longitudinal vibrations rather than traverse vibrations?

Thanks!
Peter

Has anyone tried testing a tuner on more than one different type of test bed with the same settings?
Differing results would mean a rifle tuned on a rig may not perform the same when shot from the shoulder.

You are absolutely right Gerald!

Update #2

So visited the club last night, 25 yards indoors this time. Shot from a rest in the prone position. In order to get a spread of speed I used RWS Special match and RWS R100 to give a 15m/s or 49 f/s difference in speed.

First target with tuner weight wound all the way in, one round of each, the R100 was the high shot.
Started winding out the weight, and at two revolutions out these were the results:
I carried on testing and the group opened up again. I didn't keep testing to see if there were other nodes as I was more than happy with these results (and I was cold and hungry). I did revisit two turns out to confirm the results and shot three practically indentical diagrams.

I know this was only 25 yards and will need retesting at 50m (when the weather warms up) but to be honest I shocked that two rds, one above the speed of sound and one below, can be made to hit the target in the same place! Very pleased with the results, thanks Guy.

Tony - In the first test the stock was clamped in a vice that was bolted to the floor.

Thank you very much but, what about 10 rounds together?

BR1942 - I didnt see the point in putting together a 10 rd group as the object of the experiment was to prove if the tuner was working at reducing vertical stringing by putting fast and slow ammo into the same point of impact. Which it did. A 10 rd group would just show how good my barrel ammo match is.

Perhaps when the weather warms up I'll shoot a 10 rd group at 50m with and without tuning to show any effect however I believe it will look like similar to my previous groups above, maybe a little tighter.