Help understanding load charge differences.

[Davehb]

After 30 odd years I’m trying to catch up looking at load data to develop a load, but I’m confused by something I don’t remember having ran across so much when reloading then.

Namely powder charge showing such high velocity differences + such a wide range for minimum and maximum loads for the SaME powder.   
Take power pistol: (both are loads for 124gr 9mm)
Speer shows
Hornady shows

 
Then Alliant shows charge of only 6.4gr

Everyone I look at shows max and minimum charge to be different.
Running across same for ever powder.

Have more books on the way, until then just gathering information and catching up.

Any help appreciated.


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[Davehb]

Rookie mistake.
Was looking at data for 2 different styles of 124gr bullets.

[Wobbly]

It's simple really.

• Max Load is based upon the SAAMI maximum chamber pressure allowable for that cartridge. Not the brand or model of the gun, but the cartridge itself. At the test lab where the writers of the load manual work, they will try different loads until they cross that pressure boundary. Then that load (amount of powder) is declared the maximum for that bullet/ powder/ primer combination.

Other labs doing the exact same thing will find slightly different Max Loads because of differences in local weather conditions, altitude, powder batches, bullet-to-barrel fit, and other minor differences.

[ Side Note: About 1998, most labs in the USA converted from the old Copper Units (in which the chamber pressure deformed a precision copper plug) and the pressure was then calculated. However, this method only gave a one-time "snap shot" reading of the maximum pressure, with zero indication of when it occurred or how long the chamber pressure lasted. Books published after year ~2000 used chamber pressure data collected by direct reading pressure transducers connected to computers. Understand that even a "slow" 1MHz CPU is taking 1,000,000,000 readings per second. With this much data the complete combustion cycle was finally understood. With this "new information" several load manuals had to be completely rewritten. A lot of 'favorite loads' had to be reduced, and of course conspiracy theories hit an all-time high. Bottom Line: You may have included data from sources written before year 2000 and that data is now considered unsafe. So your dad's favorite 1985 load manual may be a treasured inheritance, but you should not consult that data.]



• "Starting Load" is generally nothing more than the Max Load reduced by 10%. This is important because some (a very few) smokeless powders behave in very strange and dangerous ways when underloaded. The most famous of these may be H110 (aka Winchester 296). Another reason is "case fill". Some revolver cases designed for black powder are so cavernous, that how very dense smokeless powder is distributed inside the cartridge at the time of ignition can/will effect the results. For instance, such results are common in a 38Spcl case with 2.5gr TiteGroup.




Conclusion
While having a library of load manuals is generally a "good thing", consulting them all on every load may not be. I highly suggest that you pick one really complete, really good, up-to-date load manual as your "primary reference", say the Lyman. Lyman does not make powder, bullets or cartridges, and therefore can be absolutely neutral in their findings. And they have been in the reloading business since the 1880's so they know 'their stuff'. Then, unless you are loading something like the Hornady XTP and desire to see what Hornady has to say about their fairly unique bullet, consult only your designated primary resource.

The reason being that we already understand that no 2 load manuals agree down to the 1/10th of a grain... so why look ? The only thing that can result from consulting multiple sources is confusion... which will ultimately lead to reloading mistakes... which will ultimately lead to accidents... which will ultimately lead to missing fingers for us and our loved ones that shoot with us.


Hope this helps.

[Davehb]

Bottom Line: You may have included data from sources written before year 2000 and that data is now considered unsafe. So your dad's favorite 1985 load manual may be a treasured inheritance, but you should not consult that data.]

Really appreciate it. That’s very important information.

I had no idea the older books were considered unsafe.   

Don’t feel so bad about asking the question now. 


I was just looking up loads, powder burn rates, etc….while waiting on rest of manuals to arrive, to re-familiarize, and noticed it. 
 
Another difference between now and then is bullet technology changes such as density, hard cast, pore lead, solid copper…
Maybe I just forgot, but don’t remember so many variables that could affect increasing chamber pressures.

[Wobbly]

Another difference between now and then is bullet technology changes such as density, hard cast, pure lead, solid copper…

Very true. This is why owning a chronograph can be very important. While there are tens of variables that affect the results, most of them end up being reflected in the bullet's velocity... which we can consider as a direct result of the chamber pressure, minus other losses.

Consider that every step we take in reloading is to control chamber pressure.

Thus, based on the relationship between pressure and velocity, the listed velocity at Max Load can also be considered as the maximum velocity. The reloader is then free to use any cartridge case, bullet, primer, barrel combination as long as they do not exceed the listed maximum velocity. So the $100 chrono can for the ammeteur, replace several thousands of dollars in test barrels, transducers and computers.

As long as the listing of velocities becomes one of the requirements for the selection of your previously discussed primary reloading manual.

Maybe I just forgot, but don’t remember so many variables that could affect increasing chamber pressures.

Most of these variables are so small that we don't think about them. Say for instance, brand of brass is a much bigger contributor than temperature and humidity. That's another reason for a chrono. The chrono is looking at the end result of ALL the variables... even the ones that don't come to mind.

Regards

[Wobbly]

I had no idea the older books were considered unsafe.   

Maybe "unsafe" is too strong of a word. It mostly depends upon the brand of powder, I remember there were huge drops in the Accurate data. But industry-wide, everyone's Max Loads dropped across the board when the lab's test equipment and testing process was changed over to computer-based measurements.

At the time, all the conspiracy theorists could talk about was this being due to powder companies "lawyering up" and similar statements. There was all sorts of chest-pounding about staying with "loads good enough for my dad" and that type foolishness. It totally consumed most reloading forums for about 2 years back then. Topics you never see these days.

My point is, the reductions weren't a steady percentage across all powders. Some stayed pretty much the same, some loads dropped by a full grain or more. So it's simply best to use the latest data.

[Davehb]

Definitely helps. 
Appreciate you taking time to reply.
Got a Lyman’s on the way.

Any recommendations on a decent chronograph?
What few I found in stock reviews pretty widespread.


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[M1A4ME]

I only have a couple things to say that have made it easier for me over the years.

One is that older manuals can contain data on powders no longer in the newer manuals.  Not because the older data is unsafe but because the older powders are not the latest and greatest and many people like the new stuff because it's new and someone told them it's better.  Because I've got reloading manuals that date back into the late 70's I've got data on several shotgun powders that used to used for handgun reloading, too.  Best shooting load I've found so far for my SIG 2022 is using Green Dot powder.  Find Green Dot in a new reloading manual for 9MM loads.  That manual also has Green Dot data for .45 acp (haven't tried those yet.)

Two is that I always looked at having reloading manuals as being like having more than one car repair manual.  You'll always find info in one that's not in another one.  The majority of it may be the same, or similar, but there's always some stuff left out of one that will be in another one.

As Wobbly mentioned.  The Lyman manuals are great.  Those come closer to having "everything" you might need in them than the manuals put out by the bullet makers. 

[Wobbly]

Any recommendations on a decent chronograph?
What few I found in stock reviews pretty widespread.

• I use a ProChrono Digital. It's the same as the ProChrono, but with the addition of a Bluetooth module that will talk to your phone or laptop. There's a free app you download to your device, and with the "Digital" model all your data is neatly captured and displayed without you having to walk down to the chrono. This can be handy when you are shooting in places that you may not be allowed to walk to the chrono anytime you want. About $100 and $115 for the Digital model.

• I also hear good things about the Caldwell Ballistic Precision chrono, although I've never used one and can't tell you details. About $100.

• If you are flush with money, then the best may be the LabRadar unit. With the two previously mentioned units, the bullet passes over the unit and so those need to be located down range AND have access to a non-pulsing light source (such as the sun). But, the LabRadar unit sits on your shooting bench and uses radar to detect and measure the bullets as it proceeds down range. No special light requirements, however you may need one of those pocket-sized backup batteries since these units use a LOT more electrical power than the first 2 units. About $650.

• • All these units are offered at significantly reduced prices during the week of Thanksgiving.

[timetofly]

Another thing that will drive you crazy and doubting everything, it one manual will tell you for a certain type of bullet, that ‘x’ grains of powder will yield a certain muzzle velocity, and a different manual will say “y”  grains will give you the same muzzle velocity.  This could be attributed to temperature variations, their equipment and calibration, different test barrels, like Wobbly said “tens of variables”.After talking to tech support for a major bullet manufacturer, more or less I use COAL data from the bullet manufacturer for the particular bullet I’m loading, and if they don’t list the powders I have on hand they indicated that the bullet weight and powder charge could be “borrowed”. But as always, start with published starting loads, then work your way up.  My experience is that often a starting load is more accurate than max loads, at least in my firearms. 

Good luck in your journey

[Oklahoma Jim]

Garmin has just released a radar based chrono too.  It looks like a winner, but I haven't tried one yet.

https://www.garmin.com/en-US/p/771164

[M1A4ME]

Over the years I can tell you I almost always find the best groups at a powder charge the manual say is 100 to 150 fps slower than the maximum charge.

I bought a chrono 3 or 4 years ago.  Darn thing is still in the box.  I need to dig it out, set it up and check some loads just for the heck of it.

[Davehb]

Garmin has just released a radar based chrono too.  It looks like a winner, but I haven't tried one yet.

https://www.garmin.com/en-US/p/771164

I saw that on mid south.
Looks promising. Currently little rich for me.


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