I guess I had better explain my thoughts on this question right away, before somebody tells me to purchase a reloading manual.

OK, suppose you are working up a load with a new powder and the reloading manual does not have that powder listed in its loads. So my question is how can you be 100% safe that the load you are shooting is within the pressure allowances of that caliber.

Example: You are working up a load for a double gun and are trying to regulate both barrels etc. Better yet, you have built a wildcat and are trying to get the max in velocity out of the gun. Lets say that gun is a big bore rifle......The velocity issue being important (seems like that is the industries given velocity by PH's) because of the 2400fps you are trying to reach using a 500 grain bullet lets say.

You will NOT KNOW if the load is "within the pressure allowances of that caliber", BUT, you will know if the cartridge cases are left in a condition that they can be reused. I use the criteria of at least ten loadings out of a cartridge case. If your brass wears out before that, your loads are PROBABLY too hot. Now, I have a question for you. IF YOUR MANUAL does not show a load for a specific powder in your cartridge, HOW DO YOU KNOW WHERE TO START, WHEN DEVELOPING A LOAD?? IF YOU ARE INTERPOLATING A STARTING LOAD by the performance of some other powder, which IS given in a manual, you are inviting trouble!!

Well, I'll try to be a little more "gentlemanly" with this answer here, Mike.
Since most double rifles and double rifle cartridges are developed, regulated, and sighted with a particular powder and velocity in mind, it would probably be best to consult with someone experienced with your particular cartridge for starting loads. This will not only help you find safe loads to start with, but also help you in your quest to regulate a double- a task all it's own.
As far as wildcats, you're pretty much on your own, so a very long history of experience reloading is helpful in where to start, or somebody you can consult is mandatory. Having the pertinent information is always valuable, caliber, parent cartridge, volume of water, etc... can help you to get to the starting levels. Also, programs like Quickload are extremely helpful in finding loads, pressures, and powders as long as you understand they aren't infallible and need to be used with a degree of skepticism- read "safety factor".- Sheister

If, when you are done shooting, and both you and your equipment walk away in the same condition you arrived, you can be pretty sure your loads are safe...

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http://stevespages.com/page8.htm

It sounds like Western Powder will pressure test your loads. I don't know how they would test a wildcat. Click on "The Ballistics Lab." http://www.westernpowders.com/

OK, dumb question time:

Why would you choose a powder that doesn't have any data available for it?

With all the data that is available, online, books, etc. it seems like you'd choose something that provides data, a powder that is recommended for your specific caliber.

Yeah, sure . . . there are calibers that don't have a lot of data available, but they tend to be derivative of other calibers. Seems like you could find a derivative to put you in the ball park.

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.223 Ackley Improved Wildcat Forum:
http://www.hotboards.com/plus/plus.mirage?who=223ackleyimproved

Interesting no-one mentioned a chronograph at all .

Load down and then fire over the chronograph. Check brass as you work up. "Pressure signs" and other voodoo will get you in serious trouble nowadays. Check the brass in case of impending problems while seeking to match the velocity given in the books. Remember to adjust for barrel length.

Example: A-Squares book for the .500 A-Sq shows ~2,500fps with 118 grains RL-15. Adjusted for my barrel length my max is 2408fps at 57,000 psi. I started at 112 grains. My first shots averaged 2350fps. Think about that. Had I just "filled-er up" I'd probably have blown the rifle apart. 113 grains gives me 2385-2405fps. I have gone to 114 grains and no increase, 113.5 grains actually saw small velocity drop. I have maxed out. I load now to 2325-2350fps and I know I am well within the safety zone. I'm probably running around 55,000fps. This is with 600 grain bullets mind you. If I wanted to be excessive, I could drop to 535 grain bullets and increase velocity somewhat.

Unless you employ a pressure measurement device (transducer or strain gage) then you just don't ever know with certainty that your loads are safe. Steel and brass are very ductile and forgiving, which is why we use them. They will (usually) not give conspicuous evidence of small plastic strains (yielding), but ANY amount of plastic strain on the steel is WAY too much. We always get some plastic strain on the brass case. Trouble is that work hardened brass approaches the dynamic yield point of gun steel, so you may be far in excess of the established industry (SAAMI) pressure level before you see any evidence of "excessive" plastic strain on the case. You can be very close to catastrophic failure and see no damage to the gun. Some people posting here are pretty cavalier regarding the absolute maximum pressure level for even the strongest firearms manufactured or sold in the USA (which is 65,000 psi), but there is a reason why SAAMI selected that value and there is sound engineering behind the lower pressure levels for guns other than bolt actions with front locking lugs. Hint: if resizing your fired cases is very difficult you may have caused the chamber of the gun to permanently grow from excessive pressure. You will not see cracks and if you did that gun is now unsafe anyway, so I am always amazed by those who assume that anything short of catastrophe is OK.

Using a chronograph is an excellent idea, just abandon the notion that you may have a magical "fast" barrel because you don't see any pressure signs with that extra 200 fps. If you are still in the linear range of increasing velocity with charge weight, then you have not maxed out the volumetric efficiency of that case. However, I don't know that this condition tells you anything definite about the absolute value of the working pressure. You could still be over max pressure.

An excellent thread, gentlemen.

Pressure is an unknown factor to most of us without the test equipment previously mentioned.

Being familiar with the firearm helps so one can detect changes in any aspect of operation.

My max loads developed during cold weather are always re-evaluated before considered safe in the hot summer varmint season.

I am not interested in wearing a Remington bolt as facial jewelry...might start a new fad amongst the youngsters!

~Holmes

Ricardelli and HARALD are correct, as usual.

You measure case expansion at the junction of the solid head and case wall. Use a micrometer and measure to four didgits. When expansion equals factory ammo you have duplicted factory ammo pressure.

You see, the solid head is thick, It should not expand. The wall is thin, it should expand. The metal thickness tapers from the head to the shoulder. The outside profile of the case also tapers from head to shoulder. The higher the pressure the farther back the expansion goes toward the boltface. By measuring the fattest place on the fired case, at he pressure ring you can get a measurement of relative pressure. Just compare your measurement to factory ammo.

I figure the factory boys have spent time and money developing safe loads. They also need to conform to SAMI specs. I am thinking that they know more than me. I can use there knowledge and research to make safe accurate reloads. I do not try to hot rod my rifles. I try to make safe reliable ammo. For the most part you and I will never be able to duplicate factory ammo for safety and reliability. I do try to come as close to their product as I can though. This method is part of that end.

Oh, you could buy a strain gauge!! Maybe easiar but, certainly more expensive.

[This message has been edited by scot (edited 04-25-2002).]

Well folks, it really isn't rocket science, just go below what you consider to be a safe load and go from there. Example: Before Hogden listed a load using Varget for the .35 Rem., I looked at where Varget was on the burn-rate chart. Looked at the slightly faster, and slightly slower powders right above and below Varget. Took the safe max load of the smaller charge, and reduced by 4 grains, which gave me 34.0 grains to start with the Varget. It turns out this was a real low pressure load. I have since worked up safely to 42.0 grains and have stopped there. I, no doubt could push it a little farther with no ill results, but this load is very accurate, so I stay. When I first started hand loading, I was kinda a "velocity freak". Since then I have obtained so many different calibers, there is no need for me to squeeze the last drop, as I always have some more powerful cartridge anyway. Folks, never sacrifice safety for more power. If what you have won't safely do what you want, save to buy something bigger.

I thought Pawley could give you info based on the grains of water the case held compared to known cases.

Unfortunately, I've seen the aftermath of a couple of rifles that have let go as well as my share of set-back mauser/FN locking lugs.
With any new powder you try and find as much info as possible first with respect to other cases with similar volume and bullet weight. I intentionally start real low. With double guns I always start with RL-15. I work up slowly watching the primer, miking case expansion and bolt lift as well as ease of extraction. When I find a load thats accurate and meets all the other criteria, I fire a single case 5 times. If the primer pocket stays tight I quit. The only 100% reliable method would be a strain guage and I don't have one, but I've used this method for 30 years now on everything from .17 Rem to .50 BMG and still have all my fingers.-Rob

RobGunBuilder took the words right out of my mouth. You learn after many years to use the manuals, your chronograph, observation of the fired round, the bolt lift and how the round extracts to reach conclusions about pressures. How many times you can reload a case without having a loose primer pocket is the final test. If the neck splits first, its accurate, and vel is good, your home free. Ku-dude

[QUOTE]Originally posted by scot:
[B]You measure case expansion at the junction of the solid head and case wall. Use a micrometer and measure to four didgits. When expansion equals factory ammo you have duplicted factory ammo pressure.

will this method work for belted mag cases also?

To say that you never know that your loads are safe unless you have pressure data equipment is hogwash in my opinnion and would eliminate 99.9% of the shooters on earth...

There are certain time proven methods or working up loads that have been keeping us safe for eons..Any re-loading book will give one a clear consise picture of what can be done to prevent accidents..Handloading is safer than driving to the next town, but like anything else poop happens if you get stupid....

I start a grain or two below book max and work up, as book max these days is not quite max in most cases, when I get a shiny ring, ejector mark, flat primers, black marks, and several other indicators or slightly sticky bolt then I cut back two grains and shoot that load about 10 or more times, paying particular attention to primer seating for loose primers..You will always have one or two because of the variance in brass from case to case, toss the loose ones. I use only the best of materials in my guns. Always use new brass.

Our great forgiving grace is modern rifles are built to withstand more than we load by a great deal in order to give us a buffer zone of safty...

That's the way it has been done for the last century by reloaders, and I see no problems with this tried and true method.

Other Johnny come lately types have gone beyond these simple means, but as far as I can tell they arrive at the same results when all is said and done...It has worked for me and many others....

After all who would want to drop a fortune into the testing equipment required to test pressure in ones rifle, when he could be hunting and shooting, short of a reloading company.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com