Hot Core is the one who claimed the PRE system was calibrated. Ken Waters certainly did not. I certainly did not. If Hot Core really had a calibrated system, he could tell us how many PSI his loads produce. He cannot. He does not have a system that is calibrated in any meaningful units.

I know the formula that expresses pressure as a function of inputs that are easily gotten to three significant figures. So I know my output variable, PSI, to the same accuracy as my input variables. My strain gage system is calibrated in meaningful units. I can report PSI for my loads. I can also report pressure risetimes.

Those mythical insurmountable obstacles Hot Core imagines took me all of 15 minutes to surmount, and I do not have X-ray vision, and can't fly.

Every place Hot Core's claims are compared to reality, they fail.

Once again, Hot Core has no facts, no figures, and no physics. He has an opinion, based on an opinion he read somewhere.

Denton,



Are you using shunt resistors to cal the strain gages instead of factory ammo? If so I would expect a more accurate cal than factory ammo would provide. Another trick I picked up is to use two seperate strain gages and compare results. I don't know if your data acquisition system has this many channels, but if it does it can help reduce error generated by set-up variations.



A question to all you guys in this discussion. Is this an attempt to dethrone the "Matchking as hunting bullets" thread?



ASS_CLOWN

Im currently working up a 270 load and im not sure exactly what pressure signs are could anyone shed some light here?

First of all, welcome aboard.

Second, if you are starting to work up loads for any firearm and you don't know what pressure signs are you better put a halt to your reloading pronto!! Go out and spend the few dollars it costs for a reloading manual from one of the big bullet manufacturers and read up on pressure signs. Learn as much as you can from them.

Also, there is a wealth of knowledge on this board from people that have cumulative experience that is mind boggling. Do a search for pressure signs.

Reloading is fun, but can be potentially dangerous or even deadly if not taken seriously. Other that what is published in the books and pressure signs there is no way of telling what kind of ice you are walking on. A chronograph can be a big help also.

Have fun, but be safe...learn about the hazards and things to watch out for.

Shoow several boxes of factory ammo and keep the brass. Use it as a reference. Pay attention to how hard the bolt opens after a shot.

Read a lot. Look at pictures of overpressure rounds. The Nosler reloading guide has a few, and I am sure others do as well.

Compare your fired reloads to the factory loads. Look at primers. Compare the resistance of bolt opening. Compare to the pictures of high pressure loads.

Read the last 3 months of this forum, most of it has been coverend in some detail. Above all else, go slow!

Have fun, and welcome to the club!

My system is to work up until the extractor groove expands .001" or more measured with a dial caliper.

Then I back off 6% on the powder charge.





Backing off 6% will cost you 200 fps, but the elk you shoot will not care if you got 3300fps or 3100 fps at the muzzle.



But if you want that load for long range target shooting, then you can use less than 6% margin, when the only thing at risk is brass life, and shooting conditions are more controlled.

Above all else. Work up slow and Buy and use a decent chronograph. Use the velocity as a speedometer for your loads. Do not exceed the velocity for that bullet for that powder in your loading manuals. Most other pressure signs are not perfect. If you get difficult bolt lift, flatened primers, shiny spot on the case head, these are all sure signs that you are over by a good margin. Unfortunately the abscence of these signs in no way assures that the pressure is not still too much. Signs= HI Pressure, No signs= hi pressure maybe or maybe not. The best tool for measuring pressure at home is the M43 by Oehler. It is a thousand bucks more or less. You don't have to have that. A regular chronograph along with the other signs and a good dose of common sense will keep you out of the emergency room. Good loading shooting and hunting, "D"

I think D Hunter's advice is very good. The one exception that I would take is that you can get a PressureTrace system for under $200, and it does a very nice job.

PressureTrace? Never heard, sounds good! How does this work, and how difficult is it to use?
- mike

http://www.shootingsoftware.com/

Basically, you glue a strain gage, which is about 1 cm x .5 cm, and as thick as a piece of paper, to your barrel. I place mine under the forestock, out of sight, about halfway down the cartridge.

You do have to provide a means for getting the leads to the strain gage through the stock. My present theory is that the best way is to inlet a very small groove that comes out the top of the stock, just forward of the receiver, and to provide a little pocket in the stock to fold the leads away when not in use.

You will need to find the OD and ID of your chamber, at the point the strain gage is attached. From these two dimensions, and the known properties of steel, the system is pretty well calibrated in absolute PSI.

The PressureTrace unit hooks between the rifle and a laptop computer, through the serial port.

It gives you an oscilloscope trace of pressure vs. time, plus the peak pressure, plus the risetime.

I have one, and use it a lot. Besides my 30-06, I have one on a Mosin M39, which is hard to get "adult" loads for, and plan on putting one on a modern 6.5x55, same reason.

Hey Mike, There is one post between my two posts in this thread. When you read it, let me suggest that you imagine in the backgeound the Carny Music from Ringling Brother's & PT Barnum's the Greatest Show On Earth.

So, Hot Core, how many peak PSI does your favorite load generate? And, while you're at it, explain how you derived your answer. A man with a calibrated, repeatable system should be able to answer with no difficulty. We're waiting.