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CAUTION: This post discusses loads or load data that equals or exceeds published maximums for the cartridge(s) mentioned. Neither the writer, The Shooter's Forum, nor the staff of The Shooter's Forum assume any liability for damage or injury resulting from using this information. DO NOT ATTEMPT TO DUPLICATE THE DESCRIBED LOADS without first working them up from a published safe starting level charge while watching for pressure signs. If you don't know how to do that, don't try.

I wanted to take advantage of the new Hornady 180 grain 30-06 SuperFormance loads, but I don't want to pay the high prices for factory ammo. I went to the Hodgdon site and found a load using their SuperFormance powder here: Take Aim at Rifle Reloading Data | Hodgdon Reloading

I was able to get all the same components they originally used: Sierra 180 grain Spitzer Boat Tails, CCI 200 primers, Winchester cases. I had just two once-fired Winchester 30-06 cases, so I made more with once-fired Winchester .270 cases. I just had to run them through the '06 re-sizing die and trimmed them to minimum length.

As usual, the first strain gauge I attached got loose and one of the wires also came loose. Readings became very erratic, so I removed it and glued another one on. It has stayed on and performed perfectly.

When I finally got the unit calibrated with pressure and velocity expected from the load of 59.7 grains of powder, I realized there was some headroom for pressure. The load produces about 57,600 PSI and average 2886 feet per second. In my experience, switching from new to fired cases usually gives another 50 feet per second, or so.

Since the SAAMI maximum average pressure for the 30-06 is 63,000 PSI, I decided to see what the pressure did with more powder. I worked up to 64.7 grains powder, and the unit reads about 63,784 PSI average pressure and an average 3118 feet per second. As can be seen in the targets, the accuracy was pretty good.

I also fired a Remington 180 grain Core-Lokt and a Hornady 180 grain Light Magnum load to compare pressures with. They seem to be within velocity and pressure one might expect from those loads.

I had to inlet one of the plastic cross-members of the stock to make room for the gauge.
99636



Gauge mounted
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I also cut a small indent on the outside of the stock to allow the gauge connector to pooch out.
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Ready to test
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The last five traces here are with 64.7 grains powder
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Here are the Remington 180gr Core-Lokt and Hornady 180 Light Magnum loads. The Light Magnum load produces an
extreme velocity spread of 120 feet per second, and are not very accurate in my rifle. That's why I wanted to switch to
the SuperFormance loads.
99641


100 yards 3118 fps, .81 inches
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300 yards, 3118 fps
99643
 

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Good post. Thanks.
Is the position of the sensor critical? I assume around the case body, but does where on the body matter?
 

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Discussion Starter #3
The directions say that it should be at least a quarter inch away from the receiver and about in the middle of the case body
 

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I guess I am confused by how you calibrated your pressure trace equipment using your own reloads? Unless you tested those reloads in an already calibrated strain unit and barrel? With variations is brass and powder lots, I would think that could lead to some potentially bad readings. Other information I have read lead me to believe that you need to purchase calibrated rounds to fire in order to calibrate the gage on your rifle.
 

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The Shadow
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You do, Carp.

If you want to actually know, then you cast the chamber, and carefully measure corresponding outside thickness measurements. Then you fire reference ammo and record. That will get you within 10's or 100's of PSI.

If being within several thousand PSI is good enough, then do above but replace the reference ammo with new factory ammo. Give the mfgr your lot number and ask for it's targeted pressures.
But you must have a reference point, because the gauge isn't in the same location as SAAMI.

Placing a gauge generally overthe case, then assuming your lot of powder is about the same as the unlisted lot in a book, which doesn't tell you if or when it was actually tested; is pronounced QuickLoad.

Either "about" or QL, will give you a generality about what could be taking place; and provide a visual burning curve on some assumed things and a series of corrections by the user to make it output what you want to see.
It isn't a measurement, but it can be useful in a general way.

An example of generality:
In some of the above traces, you can see a spike in pressures near the assumed bullet exit timing. Those are known as Secondary Ignitions, they are what causes barrels to blow apart. Charlie Sisk had made a bit of a performance art, out of blowing the ends of barrels off guns with them.
We can't know if those are over-stated or under-stated in magnitude, given the approximate nature of how he set things up. But we do know that they are there, and from my work with that powder in the Creed; is likely to the point where the powder will get cranky.


Cheers
 
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Discussion Starter #6
I forgot to add the picture I took at the range. It was about 36 degrees with frost on the ground. I got there at sunrise so there was not one else around. I hate waiting to get set up or to go downrange.
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Carp:

The way to calibrate a PT (or other strain gauge system) is to build a hydraulic system for the rifle, and put an ACCURATE gauge on it. Harold Vaughn's book "Rifle Accuracy Facts" walks you through this process. In essence:

He took a fired brass case for the rifle he used, soldered or brazed a threaded plug into the neck (make sure you use solder strong enough to hold the very high pressure that will be trying to push the plug out), screwed some steel tubing into that plug, and in a way I've forgotten off-hand soldered flash hole and primer pocket shut.

After inserting the special cartridge into the chamber and closing the bolt, he carefully inserted the tubing down the barrel and screwed it into the threaded plug. From there he connected a hydraulic hand pump and gauge system, filled the assembly with hydraulic oil (it's important to do your best to remove all air from the system), and pumped up ~50,000 psi (or maybe it was a different amount; again I don't recall off hand) as his strain measurement system was on and recording.

If you follow that outline, you see what the strain gauge system reads vs. the hydraulic system gauge. There will likely be a difference, so you set that offset into the strain gauge system (the PT). Now the strain gauge system is calibrated.
 

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That is one way to calibrate but you have to remember that the strain gauge measures a changing expansion of the barrel at the chamber as it is fired. The expansion of the barrel under firing conditions is likely to be less than it will be while holding the same pressure hydraulically.
There are SAAMI calibration loads that are used to calibrate commercial gauges. I don't believe they are available to the general public so calibrations of strain gauges is approximate at best. If a person loads their own calibration loads then there is not even an approximation taking place other than to the tested load.
 

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Reference Ammunition is what you're referring to, I believe. Since it's not available publicly, bringing it up here is pointless. Further, it cannot be used to calibrate a strain gauge system in a production rifle, because the chamber is unknown.

The way Harold Vaughn calibrated (what I briefly outlined) works very well. See his book for additional detail that may help you understand.
 

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The Shadow
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There are SAAMI calibration loads that are used to calibrate commercial gauges. I don't believe they are available to the general public so calibrations of strain gauges is approximate at best.
Yes, reference ammo is available to the public, just like proof ammo is.
 
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It's up to the proof load supplier. See the notice at the top of this page at SAAMI.org. I've seen posts by gunsmiths who've had their requests declined because supplies for manufacturers were being used up too quickly. Expanded popularity the Pressure Trace may well be responsible.


Alaska_Man,

Looks like some good fun and experimenting.

A couple of technical details: The SAAMI MAP for .30-06 is 60,000 psi, not 63,000 psi (see page 29 here). As always, the numbers are devised to be safe in all guns chambered for the round and may not apply to your personal rifle. But extra pressure always shortens throat and barrel life. Also, to be sure you are within SAAMI standards, you should have no more than 4% standard deviation in your pressure readings for 10 rounds (yours from the first graph are at about 1.6% for 7 rounds) and your extreme spread of pressure should not exceed 12,400 psi for 10 rounds (yours is 2,646 for 7 rounds), The average for 97.5% of the subsequent samples of ten rounds should not exceed 61,500 psi. This all assumes the ammo is conditioned and fired at 70°±10°F and is stored at that temperature and about 60% R.H.
 

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Reference ammunition is hardly a definitive way to calibrate a commercial barrel. That ammunition is a reference for a SAAMI minimum barrel, and few if any commercial barrels are that - so the pressures will be different. Actual pressure in a commercial barrel will likely be lower, but really who knows for certain? IME the Oehler should be used as a relative pressure instrument, not an absolute one. That doesn’t mean it isn’t very useful, just that the average consumer is not a ballistics engineer working in a controlled lab environment developing ammunition within SAAMI specs (how does the OP’s testing at near 0*C effect the pressures? What will they be at standard SAAMI conditions? Who knows.).

I am puzzled by the comment that used brass gives 50 fps higher velocity than new brass. That has never been my experience, but then I’ve only been using a chrongraph for 35 years.


.
 

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i have used superformance POWDER in my 6.5 creedmoor. it was accurate and the velocity of the 120gr and 140gr nosler bt was about 50-75fps higher, not enuff of a difference.



{Edited to remove copyrighted material. See board policy on posting copyrighted material.}
 

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Discussion Starter #14
Unclenick: I stand corrected. I was going on memory for the maximum pressure of this 30-06. I should have double checked that. In any case, the action was originally a 270 with a maximum average pressure rating of 65000 PSI, so i believe the load is safe in this rifle.

Carpe Diem: I have run across several references over the years describing how new brass must be fireformed to the chamber dimensions and that takes a portion of the energy of the powder to do so. I have observed this phenomena myself many times. I wanted to try some heavier bullets and see what velocities I can get. I have some new 270 brass that I will convert to 30-06 and see if I can demonstrate this effect. I have been handloading my own ammunition for just 42 years.
 

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The Shadow
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Real interesting thread.

Curious though, what is the cause of that odd little bump at the end of the trace ??
That's a secondary ignition.
The specific cause (from the last time I read into them) is/was a debated thing without a specific answer AFAIK. Perhaps Nick has a little more insight, but don't believe it was even explained for certain.


The point of reference ammo, and the chamber casting is to have that known reference. Commercial changers are bigger, how much? Cast it. From min spec to yours becomes specifically known, and that is a set of inputs used in the set up and calibration.

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That's a secondary ignition.
Yeah, I noticed the same "lump" on some of you pressure traces in the past. Some quite dramatic.

It would be interesting to know where that sudden burst of energy comes from though. ??
 

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Wow - I wondered about secondary ignition before, light loads or unburnt powder (too slow for application). There is some report on shootingsoftware.com - it shows the secondary peak can far exceed the intial pressure. About 3/4 down the page - Nosler 7mm STW and then a 223 Rem using a 40 grain V-Max.


This is a wake up call to me. I load for some older surplus rifles.
 

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One theory is that the bullet starts to outrun the powder, then the powder gasses catch up and boot it in the rear. I don't know if it would be possible to prove that one way or another unless the acceleration of the bullet down the bore could be precisely measured.
 

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One theory is that the bullet starts to outrun the powder, then the powder gasses catch up and boot it in the rear.
That's right, I remember that now.


Wow - I wondered about secondary ignition before, light loads or unburnt powder (too slow for application). There is some report on shootingsoftware.com - it shows the secondary peak can far exceed the intial pressure. About 3/4 down the page - Nosler 7mm STW and then a 223 Rem using a 40 grain V-Max.

This is a wake up call to me. I load for some older surplus rifles.
I'm not sure what Charlie uses/used for his show. But at least for me working with Superformance, I guess you could say I'm not surprised(assuming the above theory). Supr changes it's burning curve in a "non-linear" fashion with pressure. So how I assumed/thought/hoped/etc it would react, and how it did was rarely the same thing.
FWIW

Cheers
 
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