OzFclass

Razer wrote:Hi Alan,re tuner,you mentioned that according to some experts that a small change in temperature could make your settings wrong.I presume that they were refering to ambient temperature,if so,and you fired your 12 shots in a normal course of fire,and from a cold barrel,the temperature of the barrel,plus some degree of heat transference to the tuner would surely be far greater than any change in ambient temperature??
I owned a Savage 22cal in 1960.It had a threaded end and a silencer screwed on. There was no adjustment as it was either fully screwed on or it was off.The rifle showed a marked difference in accuracy with silencer on so just the added weight on that barrel was enough to dampen vibrations.If I recollect correctly,some shooters refered to what is now called a "tuner" as a "dampener".
As silencers are now illegal I no longer own that rifle which is a shame as you could sit all day over a large warren and pot bunnies all day.
Regards,Ray.

I would ask to the specialist in tuners what can be the influence of thermal elongation of the barrel in firing?
A rise of 20°C during a shot is probably to be considered as normal, even maybe a minimal under your climates and with the steel elongation coeff, it result in some 0,2mm over the barrel lenght.
If the tuner setting is to be as precise as it is said, the tuner setting vary during a shot as the tuner moves forward under barrel dilatation???
R.G.C

Ray and Robert,

My impression was that a rise in ambient temperature will cause a rise in muzzle velocity, which will require a different tuner setting? While the ADI powders I use are single base and supposed to be relatively temperature stable, I have noticed that velocities increase significantly on hot days, perhaps more to do with the temperature of the powder in the unfired case? And that could I guess be overcome by keeping ammunition in a temperature controlled container.

Alan

Results today were less encouraging. At 600 yards, using the same tuner setting as in yesterday's testing, the first 7 shots had pretty much perfect elevation, then it completely lost the plot. A high 8 which I didn't believe, then another in the same place which I then believed, then a low 8 etc.

So.....maybe the heating up of the barrel caused higher velocities which meant the tuner setting needed changing.

At 700yds I decided to look for a compromise setting by winding it in few thou. This time it went okay (not as good as at 600) for the first 5 or 6 shots again, then went a bit low. So I got up and wound it in again and got through the shoot with no 8s, but a few 9s for 95, which I guess is okay on the relatively hard 700 target.

Conclusion so far? I need to learn more about the affect of a heating barrel, and how to change the tuner to counteract it. Looks like I'll be treating the NSW lead-up as an outdoor laboratory and hope to reach some sort of conclusion before the Queens.

Has anyone managed to find a systematic way of allowing for barrel heating with a tuner?

Alan

AlanF wrote:...... I guess be overcome by keeping ammunition in a temperature controlled container.

Alan

Gday Alan,

I reckon this may be your best bet in answer to the problem you had today. Trying to come up with tuner settings for particular ambient temps would be quite a feat!

I know that there were some top FB shooters keeping their ammo 'on ice' so to speak during the warmer months so it isnt a new idea.

This is a really an intriguing problem and the FO target provides a great medium to test it on. I will be watching your progress with interest!

Alan
To keep ammo cool I used to keep it in a small esky, that was using RE15 in the BR but I dont think thats your problem I only found that ammo temp was an issue when the temp got over 30 and that was using reloader powder which is very temp sensitive compared to ADI.

Matt P

Matt P wrote:Alan
To keep ammo cool I used to keep it in a small esky, that was using RE15 in the BR but I dont think thats your problem I only found that ammo temp was an issue when the temp got over 30 and that was using reloader powder which is very temp sensitive compared to ADI.

Matt P

Just for information, an official method of proofing when no proof ammunition is available is to heat the standard rounds in a oven to 70°C, fire imediately, and this develop 50% pressure more than the normal CIP maximal pressure...
I still wonder on the constant efficiency of tuners when temperature changes pressures and velocities, increase heat trasmission of the hot barrel to the chambered cartridge increasing from first to last round fired and thermal elongation of the barrel.
I read hereover tuner adjustments variations of very small values, certainly under the progressuve thermal expansion of the barrel from beginning of the shot to the end...
To remain logical, the tuner should be adusted progressively as the barrel heats up,IMHO.
R.G.C.

Robert Chombart wrote:...To remain logical, the tuner should be adusted progressively as the barrel heats up,IMHO...

Robert,

Thanks for the info. I am now focusing on the question of barrel length change with temperature. Do you know of any empirical data on typical thermal expansion of barrels (over a string of shots)? Obviously there are many variables, to name a few - rate of fire, thickness of barrel, and amount of heat energy produced by the particular load. Even though this information would be unlikely to be directly applicable to my situation, it may suggest some outer limits for testing.

Alan

AlanF wrote:

Robert Chombart wrote:...To remain logical, the tuner should be adusted progressively as the barrel heats up,IMHO...

Robert,

Thanks for the info. I am now focusing on the question of barrel length change with temperature. Do you know of any empirical data on typical thermal expansion of barrels (over a string of shots)? Obviously there are many variables, to name a few - rate of fire, thickness of barrel, and amount of heat energy produced by the particular load. Even though this information would be unlikely to be directly applicable to my situation, it may suggest some outer limits for testing.

Alan

Alan,
Considering a 12 coefficient of thermal expansiion and an unifirm rise in temperature of 20°C, the elongation of a 762mm barrel reach 0,19mm
R.G.C.

Robert,

To give Alan and others an idea of a possible method of obtaining a "range measurable" method of barrel expansion:

Can you give an example of a barrel- of which the dimensions are typical, and then give the increments of expansion based on the actual temperature of the barrel.

I am imagining obtaining a barrel temperature via an infrared handheld thermometer (or something like one), and putting this against a chart of some sort, with which values are known beforehand of the dimensional change. Pretty much like an elevation chart for different barrels for the same rifle.

For example:
15C = -0.005"
20C = 0.000" on tuner
25C = +0.005"
30C = +0.010" etc.

This could be estimated from the mass of the barrel somehow I guess, and the length etc. Might be an interesting project for the MS Excel hounds out there.

I've used barrel tuners on my match rifles now for six years & have found them to be generally extremely helpful.

Unlike (open) F class though, the prime consideration shooting match rifle is to cobble up a potentially efficient load that will give the maximum velocity commensurate with safe loading practices so that it (desirably) will still be supersonic at 1200 yards. In many instances, due to the barrel weight limitation rule (2.5 kg maximum), such a load will generate deleterious harmonics, which in most instances can be smoothed out with an adjustable barrel tuner. I have a couple of the now discontinued units once sold by KHGS & the 2 ounces of adjustable weight is all that I've needed, although on my first MR, I used a clamp style foresight block to get the job done. I must admit that my last barrel, which had slightly different dimensions to those I usually use, shot fine with my pet load without a tuner & in fact would shoot worse when tuning was applied.

Were I shooting a suitably-powered FO calibre, then I would be more inclined to tune by the ladder tuning method explained thoroughly by Bert Bowden some years ago in the ATR magazine.

In any case, I've seen too many of Bill Martin's foresights gently adjusted by his tunesmith to reform the group to minimum dimensions not to accept the efficacity of this technique.

John

Woody_rod wrote:Robert,

To give Alan and others an idea of a possible method of obtaining a "range measurable" method of barrel expansion:

Can you give an example of a barrel- of which the dimensions are typical, and then give the increments of expansion based on the actual temperature of the barrel.

I am imagining obtaining a barrel temperature via an infrared handheld thermometer (or something like one), and putting this against a chart of some sort, with which values are known beforehand of the dimensional change. Pretty much like an elevation chart for different barrels for the same rifle.

For example:
15C = -0.005"
20C = 0.000" on tuner
25C = +0.005"
30C = +0.010" etc.

This could be estimated from the mass of the barrel somehow I guess, and the length etc. Might be an interesting project for the MS Excel hounds out there.

Rod,
Complicated, as the heat elevation is certainly progressive from end to front, and variations in transmission can be caused by the metals tructure and other factors.
Simply put: steels have an agreed average thermal elongation coefficient of 12 (aluminium=23)
Too lazy to search for the exacts values of 416 and 4140, but variations are neglectible in this case (11 to 13 maybe)...
Elongaton is calculated:
Lenght (762mm for a 30 inches)
Coefficient of thermal exansion of alloy steel:0,000012 per mm, per degree C. of temperature rise.
Or, for a 20°C:
762 x 0,000012 x 20 =0,183mm
There are other more complicated calculation, involving surface thermal expansion and internal constraints, but we are not calculating the expansin of the Sydney Harbour Bridge, are we??
R.G.C.

water jacket around the barrel should do it AL

The you could call it the FRASER LASER
Cheers
RB

johnk wrote:I've used barrel tuners on my match rifles now for six years & have found them to be generally extremely helpful.

Unlike (open) F class though, the prime consideration shooting match rifle is to cobble up a potentially efficient load that will give the maximum velocity commensurate with safe loading practices so that it (desirably) will still be supersonic at 1200 yards. In many instances, due to the barrel weight limitation rule (2.5 kg maximum), such a load will generate deleterious harmonics, which in most instances can be smoothed out with an adjustable barrel tuner. I have a couple of the now discontinued units once sold by KHGS & the 2 ounces of adjustable weight is all that I've needed, although on my first MR, I used a clamp style foresight block to get the job done. I must admit that my last barrel, which had slightly different dimensions to those I usually use, shot fine with my pet load without a tuner & in fact would shoot worse when tuning was applied.

Were I shooting a suitably-powered FO calibre, then I would be more inclined to tune by the ladder tuning method explained thoroughly by Bert Bowden some years ago in the ATR magazine.

In any case, I've seen too many of Bill Martin's foresights gently adjusted by his tunesmith to reform the group to minimum dimensions not to accept the efficacity of this technique.

John

John,
I have not said a tuner was useless, I have said that minor adjustments can be affcted by other factors.
For TR, a clamped and indexed foresight can in some ways act efficiently as a tuner, but i think in this case, to reach the maximum of efficacity, some of the mass should be also UNDER the barrel, to compensate the added weight OVER it...
R.G.C

sh

Actually, for what it is worth, Jeff, I recon you are close to the mark. One other thing, I do not believe tuners of any sort will make a mediocre barrel become a tack-driver. What they may do, once you have a range of settings worked out for the barrel it is installed on, is "refine" the groups. My thoughts only for what they are worth.
Keith H.