Bob Kingsbury
New member
From the beginning of Genes Beggs threads on tuners, I was under the impression that his shooting facility and tunnel was controled for temp and
Humidity. ??
Humidity. ??
Keeping gun in tune.
- Thread starter russell m
- Start date
keith and bryan
i have been speculating on my having to adjust my tuner and the correct formula for doing it as gene suggest, the velocity correcting tuner i am speaking of is a 7 mag braked tuner for long range ,not a ppc sorry. but basicly at 1000yds a round aprox 120 fps slower can be tuned to hit the same poi elevation wise, between the extremes it was hoped that all velocities in between would as well but that is not the case,it seems to be 2 different accuracy nodes and by adjusting the tuner i am bringing those nodes together, so the extremes are reduced,to 80 fps tuner correction then i dropped the es to 50 fps,at that extreme correction of the tuner adjustment was made to be in the middle, meaning shots 25 fps faster then the target velocity and 25 fps slower then the target velocity all hit the same poi, I have shot on a different day at the same temp but still had to adjust my tuner to correct vertical,but still learning every day. my sky mate took a crap but the temp was the only thing i could go by at the time.so i am still waundering why since i should have been safe with 25 fps either direction. all with known a confirmed low es ammo as well , i am baffled . tim in tx
i have been speculating on my having to adjust my tuner and the correct formula for doing it as gene suggest, the velocity correcting tuner i am speaking of is a 7 mag braked tuner for long range ,not a ppc sorry. but basicly at 1000yds a round aprox 120 fps slower can be tuned to hit the same poi elevation wise, between the extremes it was hoped that all velocities in between would as well but that is not the case,it seems to be 2 different accuracy nodes and by adjusting the tuner i am bringing those nodes together, so the extremes are reduced,to 80 fps tuner correction then i dropped the es to 50 fps,at that extreme correction of the tuner adjustment was made to be in the middle, meaning shots 25 fps faster then the target velocity and 25 fps slower then the target velocity all hit the same poi, I have shot on a different day at the same temp but still had to adjust my tuner to correct vertical,but still learning every day. my sky mate took a crap but the temp was the only thing i could go by at the time.so i am still waundering why since i should have been safe with 25 fps either direction. all with known a confirmed low es ammo as well , i am baffled . tim in tx
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Jim, Gene, Bryan and all
What about that old scenario where you begin a record group in a red condition and the flags snap to green. You sit there waiting for a minute, perhaps longer with a round in the chamber. You go to the sighter and send that round through "downstairs" when the condition returns.
How many times have you seen that "overcooked" round go right where it was supposed to? Temperature increase in the chamber area should have made that overcooked round print high outside the mothball, right???
Forgive me for taking the discussion in a different direction, but I really want to get a better handle on tune. I get frustrated when I'm shooting well and all of a sudden, for no reason seem to go to pot. Believe it or not, I know when my press begins squeaking, the rifle wont group. Usually, half to a whole number reduction on the powder measure will bring the rifle back. Obviously an unscientific and unreliable way to be competitive.
What about that old scenario where you begin a record group in a red condition and the flags snap to green. You sit there waiting for a minute, perhaps longer with a round in the chamber. You go to the sighter and send that round through "downstairs" when the condition returns.
How many times have you seen that "overcooked" round go right where it was supposed to? Temperature increase in the chamber area should have made that overcooked round print high outside the mothball, right???
Forgive me for taking the discussion in a different direction, but I really want to get a better handle on tune. I get frustrated when I'm shooting well and all of a sudden, for no reason seem to go to pot. Believe it or not, I know when my press begins squeaking, the rifle wont group. Usually, half to a whole number reduction on the powder measure will bring the rifle back. Obviously an unscientific and unreliable way to be competitive.
Gene Beggs
Active member
Bob, the loading area of my facility has central air and heat, but the firing room and tunnel itself is ambient air temp and humidity. This is necessary in order to prevent mirage from affecting the sight picture. I have learned a great deal about tunnel operation in the past three years.
Originally, the firing room as well as the loading area was airconditioned. This proved to be a mistake and created a bit of mirage when the airconditioner was running. The firing room, expansion chamber and tunnel are now completely isolated from the airconditioning system. An exhaust fan at the far end of the tunnel behind the bullet trap and target frame is used to evacuate the air in the tunnel when necessary. All shooting is done with the exhaust fan OFF.
Gene Beggs
A good, relevant question. Since the thermal conductivity of brass is high (110 W/mK), the case will have heated up in one minute to near the temperature of the chamber. The thermal conductivity of gunpowder, however, is much lower (0.38 W/mK) and the air surrounding the grains even lower (0.024 W/mK), which means that while the outer grains might have heated, the inner grains probably not. With most of the grains still near the same temperature as before you chambered the round, the change in POI could be insignificant.
Cheers,
Keith
Gene Beggs
Active member
Hi guys. 
Back home from the nationals in Phoenix. Had a great time, witnessed some fantastic shooting, enjoyed visiting with everyone and looking forward to the '09 season. Lots of exciting things are looking up.
No,, I didn't win anything, but I'm perfectly comfortable with that. My heart is not in competition. I get my thrills from watching, listening, learning and searching for the keys that unlock nature's secrets to rifle accuracy. If through my products and services, I can help someone outshoot me it just tickles me to death. Rod Brown's performance at Phoenix is a good example. Rod simply left me in the dust. I love it!
Getting back to the subject of 'Keeping The Gun In Tune.' In my post #29, I said,
"Muzzle velocity may chronograph exactly the same (I have proven this) but elapsed time will be a bit less; hence, the bullet gets to the muzzle early."
Some took this to mean I was saying that muzzle velocity does not affect tune and that's not what I meant at all. Of course, muzzle velocity as well as anything else that affects in-bore elapsed time can affect tune. The key word in my statement above is "may." Muzzle velocity MAY chronograph exactly the same,,
Long ago, I learned that one cannot always tweak the load to a specific velocity and get the rifle in tune although that velocity may have shot great the day before or at a different location. The same is true of the tuner setting.
Yes, you can always start with a pet load that produces the velocity you want to shoot but you may have to go up or down as much as .6 grains to get the rifle in tune under the specific conditions.
If you are using one of my tuners you can always shoot exactly the same load regardless of location or conditions. You can always get the rifle perfectly in tune by turning the tuner either in or out no more than a half turn. If you go to the line with the tuner set to zero (12:00 o'clock) you have a one in four chance of being perfectly in tune. You can never be more than a half turn out. You can be sure the rifle will shoot with the tuner placed at 12:00, 3:00, 6:00 or 9:00 o'clock.
Some of you are trying to make something hard out of all this and it's really quite simple. Of course, changes in temperature, humidity, pressure, air conditioning vs., ambient, preloading at home vs., loading at the range, all affect tune. Common sense tells us, it is perfectly okay to load at home or in an airconditioned trailer as long as all ammunition is loaded under the same conditions.
Common sense tells us to keep our loaded rounds out of direct sunlight and that we should never leave a round cooking in a hot chamber while waiting on conditions.
Hope this helps. Please keep the good feedback coming. This is how we learn.
Later,
Gene Beggs
Back home from the nationals in Phoenix. Had a great time, witnessed some fantastic shooting, enjoyed visiting with everyone and looking forward to the '09 season. Lots of exciting things are looking up. No,, I didn't win anything,
but I'm perfectly comfortable with that. My heart is not in competition. I get my thrills from watching, listening, learning and searching for the keys that unlock nature's secrets to rifle accuracy. If through my products and services, I can help someone outshoot me it just tickles me to death. Rod Brown's performance at Phoenix is a good example. Rod simply left me in the dust. I love it!Getting back to the subject of 'Keeping The Gun In Tune.' In my post #29, I said,
"Muzzle velocity may chronograph exactly the same (I have proven this) but elapsed time will be a bit less; hence, the bullet gets to the muzzle early."
Some took this to mean I was saying that muzzle velocity does not affect tune and that's not what I meant at all. Of course, muzzle velocity as well as anything else that affects in-bore elapsed time can affect tune. The key word in my statement above is "may." Muzzle velocity MAY chronograph exactly the same,,
Long ago, I learned that one cannot always tweak the load to a specific velocity and get the rifle in tune although that velocity may have shot great the day before or at a different location. The same is true of the tuner setting.
Yes, you can always start with a pet load that produces the velocity you want to shoot but you may have to go up or down as much as .6 grains to get the rifle in tune under the specific conditions.
If you are using one of my tuners you can always shoot exactly the same load regardless of location or conditions. You can always get the rifle perfectly in tune by turning the tuner either in or out no more than a half turn. If you go to the line with the tuner set to zero (12:00 o'clock) you have a one in four chance of being perfectly in tune. You can never be more than a half turn out. You can be sure the rifle will shoot with the tuner placed at 12:00, 3:00, 6:00 or 9:00 o'clock.
Some of you are trying to make something hard out of all this and it's really quite simple. Of course, changes in temperature, humidity, pressure, air conditioning vs., ambient, preloading at home vs., loading at the range, all affect tune. Common sense tells us, it is perfectly okay to load at home or in an airconditioned trailer as long as all ammunition is loaded under the same conditions.
Common sense tells us to keep our loaded rounds out of direct sunlight and that we should never leave a round cooking in a hot chamber while waiting on conditions.
Hope this helps. Please keep the good feedback coming. This is how we learn.
Later,
Gene Beggs
Gene Beggs
Active member
You're right, sometimes things don't make sense. Everyone has seen this happen.
I like the explanation, "Yep, the wind can blow em' out and sometimes it blows em' in."
Later,
Gene Beggs
JerrySharrett
Senile Member
Gene, have you found V133 to have any different tuning window range than T/8208. I know they are not in optimum tune in the same conditions but of the conditions they are suitable for? i.e Have you found one to be more forgiving than the other?You're right, sometimes things don't make sense. Everyone has seen this happen.
I like the explanation, "Yep, the wind can blow em' out and sometimes it blows em' in."
Later,
Gene Beggs
Gene Beggs
Active member
Jerry, a great deal of the tuner testing in the tunnel was done with N133 in the 6ppc and 22-100. I have also done a great deal of work with my 220 and 6mm Beggs cartridges. I have used N133, H322, H4198, Benchmark, 8208, Norma 200 and 201, T-32 and probably some that I have forgotten. All of these powders shoot well, some better suited to one cartridge than another but all exhibit the same tuning window.
Since perfecting my tuner, I no longer tune with the powder charge. I make all tuning adjustments with the tuner and my standard seating depth is .015 off 'jam.' The load never changes.
I no longer have a PPC; my 220 and 6mm cartridges have proven so successful and user friendly, I see no need to shoot anything else.
My favorite powder in the 220 is Hodgdon's Benchmark. 27.5 grains behind a 52 grain bullet provides 100% loading density and produces around 3600 fps with outstanding accuracy.
In the 6mm , I have settled on H4198 as THE powder. 26.5 grains behind a 68 grain bullet results in about 3360 fps in most barrels with 100% loading density.
As far as one powder having a broader tuning window than another, I don't believe it matters because the width of the tuning window is determined by the frequency of the barrel, not the powder. A long, flexible barrel vibrates at a lower frequency which results in greater dwell time at the stops; hence, wider tuning window.
Regardless of which powder I'm using, I get the rifle in tune with the tuner, make a note of the temperature and position of the reference mark. If temperature increases five degrees, I turn the tuner IN (toward the breach) one eighth of a turn and so on. This formula works perfectly with every barrel I have tested regardless of caliber or powder. The tuner really simplifies getting and keeping the rifle in tune.
Hope this answers your question. Nice to hear from you. Keep in touch.
Later,
Gene Beggs
Tuning..........
Gentlemen,I'm VERY new to benchrest. I enjoy the sport immensley. I fully respect your talents and experience. I'd like to know at what yardage tuning is done. I've been trying to load develop at 200yds thinking that if it works at 2 it'll work at 1. Please advise. Thank you. gpoldblue@yahoo.com
Gentlemen,I'm VERY new to benchrest. I enjoy the sport immensley. I fully respect your talents and experience. I'd like to know at what yardage tuning is done. I've been trying to load develop at 200yds thinking that if it works at 2 it'll work at 1. Please advise. Thank you. gpoldblue@yahoo.com
Gene Beggs
Active member
Many shooters prefer to do their tuning at 200 yards. I don't think it really matters. I am of the opinion that if the gun is in tune at one yardage, it will also be in tune at the other.
Gene Beggs
Gene Beggs
Active member
Too Good To Die
Guys, this thread contains some priceless information and is too important to just let slip away.
I realize many of you have printed your own copy and of course, it's archived here on BR Central but there remains some unfinished business.
Jim Borden, you and I did not resolve our differences of opinion on weight of the atmosphere, temperature and how they affect rifle tune. I don't mean to be a pest and I'm not trying to put you on the spot, I'm simply trying to get to the bottom of this thing once and for all. Obviously one of us is on the wrong track and if that happens to be me, I want to know it.
Jerry Stiller furthered my education recently about differential threads and if I'm mistaken about this weight of the atmosphere/temperature/tune thing maybe you can straighten me out on it.
What do ya' say?
Gene Beggs
Guys, this thread contains some priceless information and is too important to just let slip away.
I realize many of you have printed your own copy and of course, it's archived here on BR Central but there remains some unfinished business.
Jim Borden, you and I did not resolve our differences of opinion on weight of the atmosphere, temperature and how they affect rifle tune. I don't mean to be a pest and I'm not trying to put you on the spot, I'm simply trying to get to the bottom of this thing once and for all. Obviously one of us is on the wrong track and if that happens to be me, I want to know it.
Jerry Stiller furthered my education recently about differential threads and if I'm mistaken about this weight of the atmosphere/temperature/tune thing maybe you can straighten me out on it.
What do ya' say?
Gene Beggs
Gene,
I have enjoyed this thread immensely. Many thanks for starting it. Here is another quote that might keep it going a bit longer: "If the bullets are exiting when the barrel is stopped at either the top or bottom of the swing, the rifle is in tune." Any comments from the group?
Cheers,
Keith
Russell,
Changes in air density is what makes our rifles go out of tune. If the bullets are exiting when the barrel is stopped at either the top or bottom of the swing, the rifle is in tune. If the atmosphere becomes less dense due to an increase in temperature, the bullet encounters less resistance as it travels down the bore and exits early before the barrel comes to a complete stop, in which case, we can either reduce the load or adjust the tuner to compensate. I think it's much simpler and easier to use a tuner. You NEVER have to change the load and can make your adjustments at the line.
Atmospheric density is the result of pressure altitude, temperature and to a far lesser degree, moisture content. Contrary to what many believe, dry air is heavier. Steam rises and it's 100 percent saturated.
So,, altitude, temp and humidity in that order. What do we mean by altitude? Range elevation above sea level. The Midland Shooters Association range is 2800 feet above sea level; that never changes so we can forget about it. Yes, slight variations in barametric pressure can change the pressure altitude but for all practical purposes, we can forget about it.
Temperature? This is the big one! It's actually the only thing you must concern yourself with. The temperature range from being perfectly in tune and being completely out is 20 degrees F.
Yep, if your rifle is perfectly in tune during the first match of the day when temperature is 70 it will be completely out of tune when the temp reaches 90 if you do nothing to compensate.
To keep the rifle in tune throughout the day, reduce the velocity 30 fps for each five degree increase in temp. With most powders, N133 being the classic example, this equates to one half click per five degrees. For example, let's say your rifle was in tune for the first match; temp was 70. Your Culver type measure was set on 54 clicks. When temp reaches 75 the proper click value is 53.5, for 80, 53, 75, 52.5 and for 90F, 52 clicks. Would you have ever believed it would take two full numbers to stay in tune with a twenty degree spread?
Relative humidity (RH) is expressed in percent of saturation at a given temperature. If RH is reported as 30%, temp 85 degrees, this means the air contains thirty percent of the moisture it is capable of holding at that temperature. If temp goes up, RH goes down and vice versa even though the amount of moisture in the air is exactly the same.
Some shooters say they adjust the powder charge by relative humidity; RH goes down, they go down on the load and vice versa insisting it is humidity that affects the rifle's tune when in fact it is the change in temperature that is actually responsible.
And BTW, you asked if changes in conditions affects barrel harmonics?" NO
Hope this helps
Later,
Gene Beggs
It sounds pretty heavy to go up two full numbers when temp drops 20f? I am not that experienced of tuning but I am going to try this.
In the meantime, buy one of those bolt disassembly tools so you can remove that little primer "wafer".
Dave Coots
64 Chevy 409 10.42 129
I'm not one to beat a dead horse back into life, but I am making this topic a way for me to keep busy while i'm at the office when things are slow. Based on some replies from Gene and CubCouper, I have some questions. I feel this is a very important for newbies like me that don't (yet) have a tuner and depend on "load tuning" to keep at the proper node. I've attached a graph based on some testing I did with my RFD Culver-type powder thrower. I threw a lot of loads at various "clicks", noting the temperature and humidity. I weighed each charge on my RCBS Chargemaster ( and on a second cheap digi-scale) to get agreement. My gun appears to be "in tune" when I throw 55 clicks, which equates to 29.8 grains of N133. The figures Gene mentioned about .6 grains between whole clicks also agrees with my testing on 'my" equipment. All that being said and paying attention to CubCouper's mentioning that at +20 degrees, another node is approaching, I got to wondering. Now let's see if i got any of this straight. i plotted a graph showing temperature versus clicks and plotted a "known sweet spot". please take a look and tell me if I were to start out shooting in the morning at 65F and the temperature rose to about 85 or 90, as it does down here near Houston, would this graph serve any purpose as I guide for tuning my load throughout the day? I realize that conditions change and that I still need to grab more weight/click relationships under various temperatures and such. Let's just say the temp, humidity, etc are such that the click/grain weight are decently accurate for now. thanks,
curtis
curtis
cwood3--I need some clarification about your graph. Your horizontal scale is temp while your vertical scale is clicks/weight. How did you arrive at the height of your dots on the graph? Is the variation in height between your dots the variance that they print on the target when you fire that load? Randy J.
No, no, there is no correlation height-wise. You could choose any scale, it would make the curve (graph line) look different, that's all. The numbers would be the same. If you go back and read Cub's post, all I did was take 10-degree temperature increments and plot them on the graph based on the combination of Gene and Cub's suggestion of clicks relating to temperature difference. This also assumes a linear relationship. Plotting a graph just going up in clicks as temperature goes down (as in Gene's post), it would be just a straight line starting high on the left and ending low to the right, however, on days with excessive temperature swings, you could concieveably get into what Jackie refers to as "the upper limit of the load range". See if that makes any sense. Again, as Cub suggested, why chase the "same node" when there is the same node travelling down the barrel right behhind the first one more or less, hence the sine wave graph that depicts barrel harmonics in many of the literature. I'm hoping Gene, Cub, or anybody will chime in. I think this is key to consistent shooting throughout a day at a match. (Now if I can just get my wind flags completed and figure out what language they speak....).
thanks,
curtis
).thanks,
curtis
AVanGorder
Adrian Van Gorder
Does anyone have such example charts for their tuners that they'd like to share?