Weighed Charges at The Nationals

[Don]

Don, a few questions.

1) Are the amplitudes of the vertical and horizontal components correlated? I.e., if you worked to "fix" vertical dispersion would it automatically help (or hurt, or have no effect on) horizontal dispersion?

2) Have you written this up somewhere? I am way behind in my reading.

3) Just out of curiosity, what is the maximum acceleration you observed?

Toby Bradshaw
baywingdb@comcast.net

1) That would depend upon the damping technique used to reduce movement. For example, a concentric tension tube would generally affect both vertical and horizontal barrel movements in the ratios that I mentioned. Another example, a verticle "mass offset weight" that Harold Vaughn used with his railgun would primary affect only the vertical barrel movement because the "mass offset weight" was only placed in the vertical plane.

2) Yes, these discussions have taken place on this messageboard, several years ago, when Harold Vaughn initially published his "Rifle Accuracy Facts" book, and many of us BR shooters were trying confirm his findings.

3) Not sure for 2 reasons; 1. accelerometer sensors have to be routed thru band pass filter and integration circuits in order to display usable oscilliscope images, which in turn obscure/alter the direct calibrated mfg. spec. readings of these sensors. 2. was only concerned about delta changes relative to various damping techniques, was not looking for precise calibrated acceleration maximum readings.

That said, Vaughn did state a 25-30 "g" maximum vertical acceleration with his rifle measurement systems....................Don

 

[Bob Kingsbury]

Once upon a time, I chronographed (oehler 33, 10ft spacing) 25grs
of IMR-4198. I had 3300 for each of 5 shots, if I recall, the sd was 1.
Using the same cases and weighed charges, I could not duplicate it.
I have never seen anything close to that again.
Normally, I see velocity go up a little for each of the first 3-4, drop
and then start up again. Thinking it has to do with the build up of
powder fouling. which then reduces it self, only to build up on succesive
shots.
It seems feasible that lighter bullets in the same case would show
greater ES than its heavier counterpart, given the same errors in powder weight. A tenth variation in powder behind a 240gr matchking,300 ultra mag
would
have to show a smaller effect than a tenth in 6ppc with 65gr bullets.
What am I missing, would love to see small ES

 

[Don]

Don,
What are you doing? Discussions like this are no place for hard data.Still shooting tuners?
Boyd

Hi Boyd,

Wish I was playing around with tuners, not quite up to it right now, although, I have several new ideas rattling around in the old noodle.

Hope to swing by and see you guys at Visalia, now that the weather is starting to cool down..............Don

 

[jackie schmidt]

Correction

I stated in my initial post that Gene Bukys did not weigh his charges. That is often true at local matches, but Gene informed me that at big Matches such as the Nationals, Super Shoot, World Qualifyers, and The World Championships, he does indeed weigh each charge.

I just wanted to correct a miss-statement........jackie

 

[B J Atkinson]

Well, it is no secret that the Australian A team in South Africa were weighing each charge. Perhaps the results speak for themselves.

We found that the local powder (S335), apart from being possibly the dirtiest powder that I have ever used, had a tendency to cause some erratic charges. I am talking as much as 6 tenths of a grain at times. I could throw ten charges and they would all be within .2gn, then you would get one out of left field. Maybe it was static that caused it, who knows. We all had quality custom powder throwers that are accurate with Australian powders. Fortunately, we picked this ambiguity up during practice, and acted accordingly.

Cheers

Brendan Atkinson