Weighing Cases & Powder

Exactly Gene.

In match conditions I (think) it may be better to have 10 really good cases, than to try to load one case ten times and shoot it in 7 minutes time for record!

As you say about the primers, all we can do is buy what works and buy all we can within the same lot. All other variables that you change at the match would be the seating depth, amount of powder, neck tension (via sizing button), or primer brand, that is if you think one brand works better in humid or dry whatever you need.

Paul
 
German Salizar

took photos and did a write up of lots of different primers while being fired from a stub barrel. Maybe German will chime in.

Shelley
 
Shelley, yes, I'm working on a larger project involving that and have been in touch with Gene since this thread began. Hopefully something interesting will develop.
 
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Tom Rose said:
Gene,
Could that spread in fps be within the standard error tolerence of the chronograph? The spread is about 1/10th or .01 of the velocity if my math is correct. :)
Click to expand...


A typical 'run of the mill' crystal oscillator is 100 ppm (part per million) or 0.01 percent.
1/10 would be 10%, or 0.1.

A bigger issue with chronographs is the interaction between the sensor spacing and the oscillator frequency.
At some point a single count of the oscillator starts corresponding to a 1 ft/s change in the velocity and the accuracy goes down for higher velocities.
 
Accuracy

Brickeyee,

What I was trying to point out is that an error of .01, which is the tolerance of the chronograph, would produce a variance of +/- 35fps at 3500 fps. Just because the machine says something, don't take the reading as an absolute. The real fps just might be closer than one would think. It would seem to me the possibility of this deviation should be taken in account.
 
Tom, 35 fps is much more variance than a good chrono will deliver. In fact, if we could only rely on them to that level, they would be of little value except for the grossest of measurements. My experience with a few different consumer grade systems and with the Oehler 43 which is sort of in-between consumer and commercial grade is that you can rely on them to a far closer level than 30 or 35 fps.
 
chronographs...

Well, how close can you rely on them? A tenth per cent accuracy is pretty good. Are you saying they are much better than this, or just a little bit better?
 
Just a thought experement.

To test the consistancy of the primers. Could you take an old barrel,thread the muzzle and screw in a pressure transducer, hook it up to an o-scope, and fire primed cases in it to measure the variation in pressure. Would that blow something? If so maybe a small hole drilled into the transducer connector would bleed off enough pressure to make it safe.

Allan
 
BLUEKNOB said:
Just a thought experement.

To test the consistancy of the primers. Could you take an old barrel,thread the muzzle and screw in a pressure transducer, hook it up to an o-scope, and fire primed cases in it to measure the variation in pressure. Would that blow something? If so maybe a small hole drilled into the transducer connector would bleed off enough pressure to make it safe.

Allan
Click to expand...

Allan, that's a good suggestion. I have thought of something along that line with installing a threaded connector into an old barrel, either leave it full length or maybe shorten it to a stub, I don't know. I thought about using a pressure gauge that had a resetable needle on it; one that would record the highest pressure reached for each shot. I didn't think about using a transducer and an oscilloscope because I'm not too savy about such things.

Tell us more.

Gene Beggs
 
Gene:

I'm not a tech wiz. I have some training and background in electronics,(But that was 30 years ago. I'm sure there are others on this forum who are more tech savey than me.
I did do some research on the transducer. www.omega.com has transducers with a 1/4" pipe thread that I'm sure could be screwed into an adapter in the end of the barrel. I may try talking to someone at omega to see what model they think would work best. For all I know you may be able to connect the output to a computer to record the results. I think it would be best to start with a long barrel to avoid building pressures to high till you can get an idea of how much pressure is produced. Wouldn"t want to blow it up. The wife gets upset when I do that!:)

Allan
 
Gene Beggs said:
Allan, that's a good suggestion. I have thought of something along that line with installing a threaded connector into an old barrel, either leave it full length or maybe shorten it to a stub, I don't know. I thought about using a pressure gauge that had a resetable needle on it; one that would record the highest pressure reached for each shot. I didn't think about using a transducer and an oscilloscope because I'm not too savy about such things.

Tell us more.

Gene Beggs
Click to expand...

Gene, a pressure gauge should work just fine and have the advantage of recording in psi which most everybody can relate to vs. voltage levels for the
transducer/scope method which is obtuse for many.

Make sure to clean the barrel of primer residue periodically or the pressure gauge valve may malfunction from said trapped residue..........Don
 
I don't think it's the primers causing extreme spread. I have used the same primers for example in a 338-404 and got consistent single digit velocity deviation where with another case for a smaller bore size would run over 25 fps deviation. Weighing primers is fruitless. Look at the sealer sometime, it's obvious the amount of sealer varies. I expect the process that puts the mixture in the cup is much more precise than the sealing process.
 
Yeah, something like that might be just what we need. I could install it in a barrel, but from that point on, someone smarter than I am would have to figure out what to do with it from there. Let us know what you find.

GeneBeggs
 
J. Pendergraft said:
I don't think it's the primers causing extreme spread. I have used the same primers for example in a 338-404 and got consistent single digit velocity deviation where with another case for a smaller bore size would run over 25 fps deviation. Weighing primers is fruitless. Look at the sealer sometime, it's obvious the amount of sealer varies. I expect the process that puts the mixture in the cup is much more precise than the sealing process.
Click to expand...

J., I know what you mean; there seems to be something that relates to case capacity vs., bore size/bullet weight. My gut feeling is the more you choke the cartridge down, i.e., big case/small bore, the more finicky it becomes and the greater the extreme spreads. Two cartridges that come to mind as prime examples of this are the 6PPC vs., the 30 PPC. Every 6PPC I have ever had showed anywhere from 35 to as much as 53 fps extreme spreads, while Jackie Schmidt reports consistently low extreme spreads with his 30PPC. I have observed the same thing with many different 30 BR's.

GeneBeggs
 
Gene Beggs said:
J., I know what you mean; there seems to be something that relates to case capacity vs., bore size/bullet weight. My gut feeling is the more you choke the cartridge down, i.e., big case/small bore, the more finicky it becomes and the greater the extreme spreads. Two cartridges that come to mind as prime examples of this are the 6PPC vs., the 30 PPC. Every 6PPC I have ever had showed anywhere from 35 to as much as 53 fps extreme spreads, while Jackie Schmidt reports consistently low extreme spreads with his 30PPC. I have observed the same thing with many different 30 BR's.

GeneBeggs
Click to expand...

I wonder if that isnt the product of; a twice as heavy 30 caliber bullet, greater mass, less percentage relative bore surface contact, than a comparable 6mm caliber bullet in the same size case capacity range and how it all relates to barrel bore variations, textures, and bullet jacket/bullet core hardness variations that ultimately influence the velocity differences? Along this line of thought, do the .22 Beggs/Russian velocity variations exceed both the 6PPC and 30PPC?.........Don
 
Decades ago I read an article, so long ago I only think it was written by Creighton Audette.
While looking for a good highpower rifle load he loaded ammo with increasing amounts of powder. The load chosen was one whose velocity varied least with slight differences in weight of powder. I think a load was chosen because if the powder charge varied slightly but accuracy stayed high, the load would perform in competition. As powder charges were lessened or increased, the accuracy quickly deteriorated.
Does this method make sense in BR?
If this question belongs somewhere else please move it. Thanks.
 
I'm inclined to believe the relatively high velocities, the low ES, and the ease of tuning the 30's provide is related to the large volume of the bore. I picture the effective "chamber" to be the volume of the space from the inside of the case head and the bullet at any given point in the barrel......the volume increases at a much greater rate than the 6mm or .22, and is ultimately much greater by the time the bullet clears the muzzle.

-Dave-:)
 
Gene Beggs

I think in Glenn Newicks book is a section saying Allie Euber was getting zero fps extreme spreads in his 6PPC but the groups weren't real good.Maybe someone can ask him?

On the extreme spreads it seems you have to reach a certain pressure point and when you do everything comes together.On a 6BR you can't reach that point with Fed 205M's because they pop when you reach 25 fps extreme spreads due too the pressure.A simple switch to the CCI 450 Magnum will keep the primer from popping and cut the extreme spreads down to around 8fps.

I know most 100 yard benchrest shooters take there bullets out of the box and shoot them without checking there weight.I think if you have a 0.7 gr difference in weight there is a very simple formula that will tell you how this affects both the velocity and the bullets bc number.It isn't a large number but at 1000 yards it matters.
Lynn
 
I have chased this thing - -

for a few years now and have decided that the ES is not very important. What is more important is to have exact charges and to have all of one's bullets positioned in the cases exactly the same where they will engage the lands.

I have seen, time after time, how a tenth of a grain can change the shape of a group or where the bullet prints on the paper. I have also seen, time after time how rounds loaded to the same OAL, measured where they will touch the lands, will change the shape of groups.

One can not always find a tiny round hole simply by changing seating depth and will need to increase or decrease the load but those are the two things that matter most, from my experience.

I have never seen any relevence to case size or weight. I have seen some relevence to the weight of bullets though. Light or heavy ones will print in a difference place on the paper.

I also found one summer that ES could be changed with primer make. That year, I found that Winchester Small Rifle primers gave the smallest ES's. I found that Fedearl LR primers gave the best ES's. I have used both since.

I don't have a tunnel to shoot in but I use to have close to it; a very sheltered slot through some Conifers into a pit. Flags never moved when I did the testing.

Anyway, I haven't exactly set the world on fire shooting but I think I show up with some of the best tuned rifles on the field. Others , better at condition reading than I, have shot very well with my gear.

In short I think I would say that it's what appears on paper that matters, not on the crono screne. ;)
 
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Dave Short said:
I'm inclined to believe the relatively high velocities, the low ES, and the ease of tuning the 30's provide is related to the large volume of the bore. I picture the effective "chamber" to be the volume of the space from the inside of the case head and the bullet at any given point in the barrel......the volume increases at a much greater rate than the 6mm or .22, and is ultimately much greater by the time the bullet clears the muzzle.

-Dave-:)
Click to expand...

Well said Dave. I agree completely.

Gene Beggs
 
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