Gene beggs makes big mistake !!!

G

Gene Beggs

Active member
Yes guys, I made a big mistake in the way I tried to explain how changes in air density affect our rifle's tune. :eek:

Now don't take what I'm saying out of context; it's not that I was wrong about what's happening, but I made a mistake by mentioning the column of air in the barrel and the fact that the bullet must push that air out against atmospheric pressure and blah, blah, blah. :rolleyes: Everyone got locked in on the miniscule weight of air in the barrel and failed to see the most important thing and that is the density and weight of the atmosphere that surrounds the planet! :mad: Some even went so far as to calculate the actual volume of air in the barrel and determine what it weighed. :rolleyes: Once the line of thinking got locked in on the air in the barrel, I may as well have been beating my head against a brick wall, so let's start all over and forget about the air in the barrel. Let's just put it this way,,,:cool:

Let's assume we are shooting at the Midland Shooter's range which is 2800 msl. Temperature is 70 degrees F. We get our rifle in tune during the first match of the morning by varying the load or if you have a tuner, by adjusting it to tune out the vertical. Let's say you are tuning with the load and 30 grains of Vitavertical shoots dots at 70 degrees, so you record the load and temp to use as your base for the day. If the gun is shooting dots the bullets are exiting the muzzle just before a positive peak on the sine wave or just after a negative. That's a given and we don't have to think about it or argue about it.

Cooler air is thicker than warm air and creates more drag on the bullet as it accelerates down the bore. If we have the rifle in tune early in the morning when temp is 70 degrees, it will be in tune only until temperature increases. Here in Midland, temperature usually increases about 20 degrees by noon and if we do nothing to compensate, the rifle will be completely out of tune when temp reaches 90 degrees. When tuning with the powder the in-tune nodes appear at 1.2 grain intervals. This means that you cannot possibly be more than .6 grains out of tune and furthermore, unless you are already up against the max load, you can get the rifle in tune by going either up or down.

So let's forget about the air in the barrel and just agree that when the air gets warmer, it offers less resistance to the bullet as it accelerates down the bore and the bullets begin to exit early. We compensate by reducing the load slightly. How much? .6 grains for each 20 degree increase in temp. Or,, .15 grains for each 5 degrees increase; .30 grains for each 10 degrees. If you're using a Culver type measure, each number on the dial represents .6 grains of Vitavertical; each half number is of course .30 grains which is the smallest correction I bother to make. If my rifle is shooting dots at 70 degrees and 54 clicks, I'll reduce the load to 53.5 when temp reaches 80 degrees, 53.0 at 90. Clear?

"Oh but Beggs, I thought you tuned with your tuner!) :eek:

Yes, I do but I'm just trying to keep things simple. Very few centerfire shooters use a tuner but as more and more discover how well they work, that will change. ;)

Hope this helps. Fire away, I'm taking cover. :p

Gene Beggs
 
Gene,
Just out of curiosity why are you going down and not up with the charge. I understand if you are at max the only way is down. But using your example of 54 clicks why not 54.5 and then 55 clicks. According to your calculations we should still be in tune!!
Dana
 
Dana said:
Gene,
Just out of curiosity why are you going down and not up with the charge. I understand if you are at max the only way is down. But using your example of 54 clicks why not 54.5 and then 55 clicks. According to your calculations we should still be in tune!!
Dana
Click to expand...


Hi Dana

Yes, you could do it that way if you shoot in the middle or lower window. Most shooters today are using max loads and there is only one way to go; down. Thanks. Good point. ;)

GeneBeggs
 
What Gene is describing is exactly what I have found. For each 10 degree rise in temp I either drop my charge .3 grains or alternatively increase charge .9 grains.

That said, I didn't have a lot of luck in the upper node this past weekend at Rachel's Glen, but the mirage was so bad that it's entirely possible that was the problem and I just wasn't aiming where I thought I was. I finally had the mirage figured out Sunday afternoon and was shooting well, then had a train wreck chasing a high shot on my fourth group.
 
Gene:
Do I have this correct???

Upon arriving at a new range 1 day early to practice for match.
At 3PM and 80 degrees your gun is shooting dots with 54 clicks V133

Next day 8 AM and 50 degrees (Match Day) for your first record group your load would be either 55.5 clicks or 52.5 clicks.

I assume there has not been barrometric pressure change these 2 days.
If that occurs then all figures for loads are in question?

CLP
 
Gentlemen ...

With all due respect, I believe I like this philosophy more each day because it's much simpler and easier to remember and carryout.

Hall of Famer Jim Borden:

"I have my ammunition already loaded for [major matches]. It's working, both rifles are Agging in the 'low Ones', with a load of about 29.0gr N133, running about 3300 fps.

Loading to conditions on match day can kill you. All you can do is go by memory and guesstimates. If your rifle has good vibration control, you'll typically have an accuracy window of 100-125 fps.

I set preloads for velocity in the middle of the accuracy window which lets me shoot in any conditions."

:)
 
abintx said:
With all due respect, I believe I like this philosophy more each day because it's much simpler and easier to remember and carryout.

Hall of Famer Jim Borden:

"I have my ammunition already loaded for [major matches]. It's working, both rifles are Agging in the 'low Ones', with a load of about 29.0gr N133, running about 3300 fps.

Loading to conditions on match day can kill you. All you can do is go by memory and guesstimates. If your rifle has good vibration control, you'll typically have an accuracy window of 100-125 fps.

I set preloads for velocity in the middle of the accuracy window which lets me shoot in any conditions."

:)
Click to expand...


Interesting. I wish I had barrels that were as sweet as the ones Jim must be using! ANd a log book and notes make it so I don't have to remember or take guesses.
 
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Gene, I have to say that the longer I do this the more I'm starting to believe that .6 gr of VV133 will take you from tune to completely out of tune. The one thing that seems to still remain a mystery to me is how to ride that tune over a 2 day match. At this time the best I can do is try different loads at the line and shoot what looks best at the given moment. The nice thing about the .6 gr thing is I spend less time dancing all over the place and can usually find the tune again pretty quickly.
russ
 
goodgrouper said:
Interesting. I wish I had barrels that were as sweet as the ones Jim must be using! ANd a log book and notes make it so I don't have to remember or take guesses.
Click to expand...

Try a Borden GUN ;) they get an amazing percentage of good barrels.....

al
 
Russ Hardy said:
Gene, I have to say that the longer I do this the more I'm starting to believe that .6 gr of VV133 will take you from tune to completely out of tune. The one thing that seems to still remain a mystery to me is how to ride that tune over a 2 day match. At this time the best I can do is try different loads at the line and shoot what looks best at the given moment. The nice thing about the .6 gr thing is I spend less time dancing all over the place and can usually find the tune again pretty quickly.
russ
Click to expand...


Hi Russ

Yep, you are so right about that .6 grains. There are two ways you can "ride that tune" over a two day match.

1. Reduce the charge .3 grains when temp increases 10 degrees. Reduce it another .3 grains when temp increases another 10 degrees. It's a 20 degree range.

2. The best way and also the simplest is to use one of my tuners. You NEVER have to change the load and you can NEVER get caught at the line with a block of cartridges that are too hot!

Gene Beggs
 
Gene,
We all like to know how things work, and a lot of these explanations involve some degree of supposition rather than direct measurement, which may be difficult. Recently, someone told me of situation where a highly rated shooter, who has switched to using weighed charges was unable to find tune that way under a given set of match conditions, and was able to do so when he got out his measure. I would guess that the reason was that he has years of experience working by volume, and months by weight. It would be interesting to have the weight of the charge that finally worked. In any case, back to my point. If we resist the temptation to say "this is how it works" and simply report that when this happens, I make such and such change and it seems to correct the problem, or that the most reliable correlation that I have found between range conditions and tuner adjustment is with DA, there can be no argument. DA is measurable, as are group size, and tuner adjustment. At that point, the only question is whether your results can be reproduced by others; if they are, then we are done.
 
C.L. Peterson said:
Gene:
Do I have this correct???

Upon arriving at a new range 1 day early to practice for match.
At 3PM and 80 degrees your gun is shooting dots with 54 clicks V133

Next day 8 AM and 50 degrees (Match Day) for your first record group your load would be either 55.5 clicks or 52.5 clicks.

I assume there has not been barrometric pressure change these 2 days.
If that occurs then all figures for loads are in question?

CLP
Click to expand...


You are correct and a drastic change in barometric pressure will affect the load. Once I got my tuners perfected, I quit making any adjustments with the load. I also don't try to carry over tuner settings from one day to the next. For the first match of the day, I go to the line with my pet load, which never changes and get the rifle in tune with the tuner using the procedure I outlined earlier. Once tune is found, I make a note of the temperature and tuner setting and use that as my base for the day. If the rifle dialed in at 70 degrees with the tuner set to 3:00 o'clock, I will set the tuner to 6:00 o'clock when temp reaches 80 degrees and so on.

Gene Beggs
 
Direct measurement, which may be difficult.

No doubt and as I was recently reminded, performance will be defined at target.
Tuner or not. There is no shortage of variables and no single “Holy Grail” answer.

NC is recalcitrant in the environment (Weather). Weather occurs primarily due to density (temperature and moisture) differences between one place and another. Temperature differences cause pressure differences and "Density Altitude” is the pressure altitude adjusted for non-standard temperature. Additionally, possible Physical properties changes and the impact on peak pressure from varying temperatures.

I’ve tried the pre-weighed charges and think pre- loaded results are more favorable. Performance would be maximized using reference STP conditions, as long as you stay within a predetermined temperature and location. I think……

Ken

Ref: Google
 
Humidity

While humidity plays a part in poi, Maybe more so for the long rangers than the short br's, it also has to play a part in the reloading issues of each day.
That is to say that when you load at the range you are loading air however small into the case that has varying humidity from morning till afternoon.
So also is our powder being subject to the same humidity in the hoppers or in the loading trays and also the primers.

For those that would preload whatever the humidity at the loading bench that would be it. Unless of course you are bringing weighed charges and dumping them at the range then you are back to the same humidy issues as the rest of us.

So it would seem.
 
Vern said:
While humidity plays a part in poi, Maybe more so for the long rangers than the short br's, .
Click to expand...

Not really. Ballistic programs show not much more than a 4" difference at 1000 yards between 1% humidity and 100% with many popular bullets. It's small enough it can be discounted entirely. I mean, you can easily get more than 4" variation at long range with wind, mirage, or velocity deviations at those distances.

As to the other possiblities you mention, they have more potential to influence things but no one really knows for certain as to the extent of it.
 
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I may be mistaken, but

since I am a newbie please have patiences with me. When CL Peterson responded about a 30 F change in temperature, He inidcated that y ou would move up from 54 clicks to 55.5 or down to 52.5 clicks. From what Gene said earlier your can be no more than .6 grains (1 full click ie. 53 to 52 or 53 to 54 ) out of tune. I seems to me that if the temperature decreases by 30 F then the adjustment would be down by 1.5 clicks or up by .5 clicks!! Is thisa right or have I made a mistake somewhere in my logic (if I have any?)

Also, I would think the more appropriate direction to move would be up not down when the temperture went down. Is this correct?

And finally, is it relatively accurate that all barrels show nodes at approximately 1.2 grain intervals??
 
Dubois Dave said:
since I am a newbie please have patiences with me. When CL Peterson responded about a 30 F change in temperature, He inidcated that y ou would move up from 54 clicks to 55.5 or down to 52.5 clicks. From what Gene said earlier your can be no more than .6 grains (1 full click ie. 53 to 52 or 53 to 54 ) out of tune. I seems to me that if the temperature decreases by 30 F then the adjustment would be down by 1.5 clicks or up by .5 clicks!! Is thisa right or have I made a mistake somewhere in my logic (if I have any?)

Also, I would think the more appropriate direction to move would be up not down when the temperture went down. Is this correct?

And finally, is it relatively accurate that all barrels show nodes at approximately 1.2 grain intervals??
Click to expand...

Welcome Dubois Dave! :)

If I may make a suggestion..... write all this stuff down and then go try it yourself. It has been my experience that making assumptions based on other people's equipment/powder/locality/experience is a recipe for disaster.

al
 
goodgrouper said:
Not really. Ballistic programs show not much more than a 4" difference at 1000 yards between 1% humidity and 100% with many popular bullets. It's small enough it can be discounted entirely. I mean, you can easily get more than 4" variation at long range with wind, mirage, or velocity deviations at those distances.

As to the other possiblities you mention, they have more potential to influence things but no one really knows for certain as to the extent of it.
Click to expand...

Ballistic programs don't take into account the muzzle position on the sine wave.
 
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