Powders for 308

Shadow9mm said:
Still in progress. Bad weather. Hoping to test again within a week or so. Going to finish pressure testing, and start testing for es and SD consistency.
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Makes sense, Since I got the Lab Radar I have been pressure testing and collecting velocity data at the same time. Also watching for accuracy. I do not place a whole lot of interest in the accuracy until after I have nailed down the ES/SD I am looking for.

I will post my results in a thread for you to view so we can compare data that we collect.
 
easiest way to cool a barrel between strings drape a few wet paper towels over it for a couple of minutes.

Bart, why square and shim a bolt face. I thought you a proponent of the theory that the cartridge's lay in the chamber at an angle ? If the cartridge is tilted then the bolt head will never be parallel to the case head no matter how square the bolt head is to the bore


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Ontopic - just screwed together a .308 with a temporary barrel and have a bunch of 168 Noslers and BLC 2 I loaded a while back for my AR10. I am not expecting much accuracy, this barrel is a stock Savage 20 inch fluted barrel which was a 1 MOA rifle when I pulled it. I am waiting on a custom barrel but I am curious to see how much if any difference I will see using a better trigger and stock. The intended barrel won't be here for a month or so
 
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Shadow9mm and kilotanker22, how are you guys planning to measure chamber pressure? While I would be curious as to the results I am wondering what method you plan to use to get the data.

Ron
 
hounddawg said:
Bart, why square and shim a bolt face. I thought you a proponent of the theory that the cartridge's lay in the chamber at an angle ? If the cartridge is tilted then the bolt head will never be parallel to the case head no matter how square the bolt head is to the bore
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Can't speak for Bart, but I can tell you Harold Vaughn showed additional recoil moments are introduced by out-of-square or unbalanced chamber configurations that add to group dispersion. Additionally, for the handloader, if the bolt face isn't square, you get out-of-square head fireforming of the case that the resizing operation doesn't fix. These cases, in turn, expand to bump the bolt face on one side before touching the other. That introduces another minor recoil moment that opens groups up unless you can put the high side of the head in the same orientation in the chamber each time.


Reloadron,

Since the Oehler 43 is no longer made, you usually buy one of these: Pressure Trace. If you have the money to put into it, you can also buy a universal receiver and a piezoelectric transducer system, but it's not cheap.
 
hounddawg said:
Bart, why square and shim a bolt face. I thought you a proponent of the theory that the cartridge's lay in the chamber at an angle ? If the cartridge is tilted then the bolt head will never be parallel to the case head no matter how square the bolt head is to the bore
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Good reasoning.

Yes, the chambered round is a teenie tiny bit crooked in the chamber. An insignificant amount. Angle spread of bolt face to case heads gets bigger if the bolt face is not squared up. Problems are minimized, not eliminated.
 
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Additionally, for the handloader, if the bolt face isn't square, you get out-of-square head fireforming of the case that the resizing operation doesn't fix. These cases, in turn, expand to bump the bolt face on one side before touching the other. That introduces another minor recoil moment that opens groups up unless you can put the high side of the head in the same orientation in the chamber each time.
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maybe so, but a 5 mph fishtailing head or tail wind trumps all
 
All we can do is limit the variables within our control. When it comes to the influences of nature, lady luck often has the final word.
 
All we can do is limit the variables within our control. When it comes to the influences of nature, lady luck often has the final word.
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you think . Recently was at match where wind was kicking everyone's butts. Average scores were mid 190's for 30 shooters, then the guy I was scoring pulled a 199 13X. Other two targets were mediocre. That 199 showed what the shooter, the gun and ammo were capable of when the everything went right. Rarely do things go right 20 shots in a row for most of us.

5201 things to think about and allow for when on the line, whether my bolt is squared is not one of them
 
Start shooting a test group on the range a half hour before sunrise when the wind is very calm.

Square the bolt face when the first new barrel's installed then no further thinking about it is needed.
 
Unclenick, thank you.
Reloadron,

Since the Oehler 43 is no longer made, you usually buy one of these: Pressure Trace. If you have the money to put into it, you can also buy a universal receiver and a piezoelectric transducer system, but it's not cheap.
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I have looked at Pressure Trace and given some thought to making something similar using strain gauges I have. I have worked with strain in the past including mounting strain gauges. Still have several of the old Micro Measurements 350 Ohm gauges and still have an old Omega strain gauge bridge completion module. Got various data acquisition modules laying around including some fast ones. Nothing to lose by trying it.

Not quite ready to buy a Piezotronics conformal ballistic sensor. I was just wondering what others were using.

Thanks
Ron
 
If I was building a pressure test barrel, it would be a two piece one. The chamber section would be threaded into the rifling section. Re-rifle as needed. One chamber section for each pressure system; best for comparing CUP to PSI with the same freebore, and throat plus rifling dimensions.
 
Reloadron said:
Shadow9mm and kilotanker22, how are you guys planning to measure chamber pressure? While I would be curious as to the results I am wondering what method you plan to use to get the data.

Ron
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To be clear. I am testing for pressure, not measuring pressure. Meaning I run the load from start to max looking for things like flattened or cratered primers. Ejector swipes on the brass. Or stick bolt/extraction.

My goal is to get to max with no pressure signs. then I work back down from max, testing for good SD and ES. After that is the seating depth testing.
 
Reloadron said:
Shadow9mm and kilotanker22, how are you guys planning to measure chamber pressure? While I would be curious as to the results I am wondering what method you plan to use to get the data.

Ron
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I do not actually test chamber pressure. I guess, a more appropriate term would have been "testing for consistent pressure".

To accomplish this I simply measure velocity in ten round strings. I record velocity spreads and adjust my powder charge and primer choice until I am able to achieve what I consider to be a tight velocity spread. To me an acceptable velocity spread means an extreme spread of less than 20 fps.

My theory is that inconsistent pressure will not yield consistent velocity spreads. While doing this, I also watch for signs of excessive pressure. For excessive pressure, I watch for the obvious signs along with velocity. So I do not actually measure the pressure. I only measure velocity as an indicator of pressure consistency.
 
I've shot proof loads in Garands developing about 67,500 CUP (82,000 PSI) that most people thought "pressure signs" looked maximum and safe. Others thought a bit warm but safe like their regular service ammo. Normal pressure is 50,000 CUP (60,000 PSI).
 
Bart B. said:
I've shot proof loads in Garands developing about 67,500 CUP (82,000 PSI) that most people thought "pressure signs" looked maximum and safe. Others thought a bit warm but safe like their regular service ammo. Normal pressure is 50,000 CUP (60,000 PSI).
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That is why I do not exceed published max data. I will go to max, but not beyond. Each gun is somewhat of an individual so I test start to max when working up a new load, just to make sure I am not getting any odd pressure signs.
 
Kilotanker22 and Shadow9mm, thanks for sharing that. I was just curious.

Bart, if I were to invest in doing it I would only go with the piezo transducer method. When doing other forms of pressure testing I spoke with and looked at the equipment Piezotronics uses for ballistic testing. Really nice stuff and I only spoke with them briefly about ballistics since that was not quite what I was supposed to be discussing with them. :) While the CUP method is fine and served for decades I really like looking at an actual pressure curve with respect to amplitude and time in a plot. I can't get that measuring a copper pellet before and after. While nowhere on par with the piezo transducer method I hope to try using the method that pressure trace uses since I have the stuff laying around to do that.

While SAAMI proof testing ammunition can exceed max load pressures for rifle by 30 ~ 44% I have never had any desire to push things that far. Doing it right not only involves firing proof test ammunition but after firing disassembling the complete rifle and measuring every part for changes brought about by stress. They also get into round counts of how many proof rounds were fired. Julian Hatcher did a lot of work with proof testing on 1903 Springfield rifles.

Like most I remain below maximum loads but have no problem loading max and working down and observing velocities looking for good accuracy and small standard deviation numbers. Keeping it simple. :)

Ron
 
That depends on how you evaluate the group. If you track each shot's location, then a large group evaluated by radial standard deviation is best. If you track only the group diameter as determined by the two furthest-spaced shots in your groups (group diameter) it turns out that firing 7-shot groups and averaging the diameters of several of them get's you to statistical nirvana with the fewest number of rounds fired. A paper covering this and how many groups of 7 you need to get certainty within different percentages is here. It says the average diameter of 6 groups of 7 shots (42 shots fired altogether) gets you to within 15% error expected for an infinite group count with 90% confidence.

The radial standard deviation method will do that in 15 shots with 95% confidence, so probably about 13 shots for 90% confidence, which is just one more than the number of holes you are including in your measurements of the extreme spread of six groups of 7. The radial SD method is the most ammunition-economical method, but you do need to know where each round lands to use it.
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I roll with the CEP method myself, if I can keep my CEP below .5 MOA then all I have to do is read the wind and put crosshairs in the right place. Simple huh :)

https://military.wikia.org/wiki/Circular_error_probable


Bart - I establish my scopes windage zero when I first install the scope and waterline @100, chrono for ammo velocity and work up a dope card. At a match however the wind speed and direction can change radically through a 8 -9 hour match. You have to adjust and adapt, changing POA or clicks accordingly

For the curious this link explains why a fishtailing head or tail wind is the most difficult to call and can push a shot out of the X and into the 8 ring. I'll take a 15 mph crosswind over a 5 mph headwind any time

Not about reloading but a good read for both short and long range shooters.
https://bisonballistics.com/articles/why-headwinds-are-more-difficult-than-crosswinds
 
A 5 mph headwind from 12 o'clock has the same effect as a 7.3 fps slower muzzle velocity. Bullet will strike only a tiny bit lower. There's no wind to move the bullet horizontally.
 
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and what if that headwind is veering between 0°, 375°, and 15°
Bart, try reading the link I provided and learn

It's NOT the Vertical
 
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