why reloading data varies

[ralphc21]

Can anyone tell me why it is if you look up a load data in three different books you get 3 different amounts. for example Hornady 45 230gn unique thet call for starting with 5.1gn while Speer 45 230gn unique calles for 6.4 and Modern Reloading 45 230gn unquie calls for 6.0gn

[Sevens]

It's not an exact science. Each data source lists their testing methods and the components they've used. Barrel length, brass, primer, bullet shape, all of these can be different. Not to mention the equipment they did their testing with and the peak pressure they built their data to.

Loading data is not a dead-set recipe. It's more like an outline or an example.

[Jim243]

I have observed that OALs vary from book to book as well and there is the safety factor each book will use to make sure you do not blow yourself up using their data, that would make their lawers unhappy not to mention their insurance company.


Jim

[GeauxTide]

Same thing can be said of two identical rifles in the same caliber. One shoots better than the other. Two identical cars. One is faster, slower, gets better, poorer gas mileage. I just built three identical servers. Two work and one don't.

[Jim243]

Make sure each server has a seperate "name" ortherwise you will get a conflict and one will work (first turned on) and the other won't.


Jim

[Clark]

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

The Alliant max load for 45acp 185 gr is 8.2 gr Unique.

I put 10.8 gr in a little 20 ounce Patriot 45, and the recoil was intolerable.

Maybe some of the load developers, that wrote the books, were wearing gloves.

[SL1]

Ralphc21,

You actually ask a good question. Modern reloading manuals from reputable bullet and powder manufacturers are SUPPOSED to be based on pressure testing done with barrels built to tight specifications and and procedures published by SAAMI. While there are SOME differences to be expected from using different bullets, cases, and primers, there are plenty of examples where the differences appear to be too large for those factors to be totally responsible for the charge weight differences.

But, if you also look at the differences in the LOT NUMBERS of the powders used, you can probably rationalize any remaining differences. Powders of the same brand and name can and do vary a lot in their burning rates, and thus the pressures that they create.

That makes it harder for us handloaders, especially if we are shooting low-pressure cartridges that do NOT display any observable pressure signs at pressures above the proof-pressures of some of the guns that they are used in.

Velocity data that is in the manuals is different and somewhat misleading. Typically, the manual will provide charge weight data that was developed in a pressure-test barrel, but the velocities published with those charges are usually NOT from the test barrel. Usually, the velocities are taken from the same loads when fired in ANOTHER gun that is commercially available. The stated purpose for that is to give handloaders a "realistic" expectation of the velocities that they will achieve with those loads in commercially available guns. Because the chambers of the pressure-test barrels are made to minimum dimensions, they usually produce higher velocities than chambers in commercial guns (provided that the barrel lengths are the same). But, the velocity variations due to chamber variations in commercial guns are quite large. So, putting "apples and oranges" data in the manuals prevents us from getting a really good understanding of how velocity readings relate to pressure with a particular load. I wish they provided BOTH the test barrel velocity AND the velocity from a specified commercial gun. But, none do that.

SL1

[GeauxTide]

Make sure each server has a seperate "name" ortherwise you will get a conflict and one will work (first turned on) and the other won't

The name and IP only have to be different after boot and OS is applied when: 1. Adding the server to the network. 2. Adding the server to the domain. We always burn the server in for a few days beforehand.

[Nevmavrick]

Clark
If you read that max usable was 8.2 gr, why would you boost YOUR load by 25%???
Just askin'.
Gene

[WESHOOT2]

The additive differences from including all variables render "data manuals' as guides ONLY.
This is why ALL manuals state "Start low and work upward". And some of us (loaders) recognize the utter reality of "in MY gun" and "Unless you test you guess".

EVERY ASPECT of the ammunition, and test equipment, and loading AND test environment, remains a variable.
So the results in data vary.
Ay?

[NCMountain]

Like one of the posters stated, not an exact science. It comes from each company doing their own testing to get what they consider a start load and never exceed load usually.

Once you do it for a while and shoot alot you will soon find your favorite loads either by the manual or from experimenting within the ranges given.

That is the beauty of this hobby. Everyone has a "pet load" they just like better than anything else.

[Sevens]

Clark
If you read that max usable was 8.2 gr, why would you boost YOUR load by 25%???
Just askin'.

I'm sure he can answer for himself but he doesn't show up as often as many, so I'll insert a comment.

I use to think he was just some nutbar myself... but he actually goes out and buys cheap (but SAAMI spec) firearms and then purposely overloads them and discharges them from a distance to see what it takes to grenade them.

I'm not sure how useful his data is, but I do find it quite interesting!

[temmi]

It is not really that hard once you understand the diff in components.
Bullets vary in
Bearing surface
Jacket makeup and hardness
Lead hardness
They may use different brass & primers in their testing.
Different lots of powder
Even different pressure barrels .
Also they may draw the line (pressure wise) in different places.
IMO it is a mistake to just substitute bullets for the same powder charge… work up.

[Tex S]

Clark
If you read that max usable was 8.2 gr, why would you boost YOUR load by 25%???
Just askin'.
Gene

THIS POST CONTAINS OVERLOAD DATA! DO NOT USE IT!!!

If you saw some of Clark's 10mm overload data you would flip out. How about an 82% overcharge of 800x in a Glock 20 w/ a Barsto barrel? His notes indicated there was a "small bulge" on the case.

I was really surprised at some of the overload data that showed no ill effects... not even a bulged case or loose primer.

Reloading manuals are merely a guide. I'm not saying go crazy with your loads, but obviously some manual listings are nowhere near "max".

[SL1]

The idea that you can "work-up a load by looking for pressure signs" and stay below SAAMI pressure specs for your gun is really only applicable to high-pressure cartridges that run higher than at least 50,000 psi, probably more like 65,000 psi if you are waiting for a "sticky bolt lift".

For cartridges with pressure limits down around 15,000 psi, there really aren't any reliable pressure signs to look for.

A choronograph can give you some reason to believe your pressures MIGHT be too high if your velocities are unexpectedly high, but the reverse is NOT true. For example, a revolver with a large cylinder-to-barrel gap may be giving low velocities even when the peak pressure is well above the SAAMI limit.

An auto-loader can give you a hint by how far it ejects the brass, but a handload with a fast powder and heavy bullet can give softer ejection than factory rounds while still producing peak pressures well above SAAMI limits.

So, staying safe when reloading for weak guns that shoot low pressure limit cartridges depends a LOT more on the data in the manuals than the usual advice would seem to indicate.

SL1

[Unclenick]

I've seen lot number changes on some powders, Winchester Ball, for example, change average pressure by 10% or so from the same charge weight. Since the same material ingredients are used from one batch to the next, the energy content is fairly consistent even if the burning rate isn't. As a result, when that pressure goes up from lot burning rate increase, the velocity goes up because acceleration of the bullet is higher earlier in its travel. It's not a huge increase, in the ballpark of being very roughly proportional to the fourth root of the change in pressure, but it's there.

So, if you have a good chronograph placed at the same distance from the muzzle that the manual authors used (usually 15 ft to the center between the screens, but ask if in doubt), you can begin with the lowest starting load among the published ones and start incrementing the load up from there, watching both velocity and pressure signs. If your barrel length is the same as the barrel length used in the test loads, then you can use the manual maximum load velocity as a secondary limit. That is, don't exceed the highest maximum charge or don't exceed its published velocity, whichever you reach first. That will keep you from exceeding their pressure. If your barrel is not the same length, you can use a program like QuickLOAD to find the velocity ratio you are likely to see with that same powder load and still use that as a secondary indicator.

Obviously, whether you want to remain within the manual pressure limits or not is a separate decision, but do use every indicator you can to be aware when you are making it.

I was unaware of Clark's experiments, but that sure explains some of his posts. Blow-up pressure is one thing, but in auto pistols you want to consider frame battering and extractor hook stress and other pressure-related factors; not just pressure containment. A gun that tolerates a very high pressure load without damaging its barrel or chamber, but which is over-stressing its other parts when shooting them is not really a combination you want to take to a fight from a reliability standpoint.

SL1 is quite correct that there is no way signs of any kind can give you a precise pressure like the SAAMI limit. You are just looking for how your brass and steel interact. Some revolvers with thin cylinder webs will give you sticky ejection at lower pressures than rifle loads give. Primer flattening is unreliable at handgun pressure levels. Revolvers have been burst by cases that had normal looking primers in the remains of the head.

[bobelk99]

The additive differences from including all variables render "data manuals' as guides ONLY.

Bears repeating 1000 times.

[Clark]

I started handloading ~11 years ago with a rockchucker kit.
It came with a load book, "Speer 12" 1994.
I read that book like any good engineer would, looking for trends and principals in the numbers of the loads listed.
I assumed they did some pressure testing.

You know you are a nerd if you can study for hours on charts of stars, stereo specs, integrated circuits specs, transistor specs, steel specs, etc.

I thought I could figure out the principals of internal ballistics by looking at Speer 12.
I tried for a long time, until I figured out that the data had been faked.
They dry labbed the data.
All the loads were listed in a hierarchy of velocity, but were all at different pressures. The starting load velocities were a ratio of the max load, calculated with an inaccurate formula.

I was really angry. Like when I found out that "Ice Road Truckers was scripted, staged, and the trucks were empty. The Modern Marvels John B. Denison story was real, and I was seamless dovetailed into being conned by the fictional series.

I hate being made a fool of, and "Speer 12" fooled me for months.

I had made good money over the years by designing switching power supplies for various aerospace and medical clients. I disabled the protection and over stressed them until they blew up like firecrackers. I then improved the design per the failure. This technique is sometimes called HAST.

So I bought guns, and over stressed them with hot handloads.

My father, chief engineer of a fortune 500 company for 40 years and has dozens of gun patents, told me I was crazy for blowing up guns. I showed him my data, and he said is was ok then. I was pulling trigger strings in 2000, and he was pulling trigger strings in 1950.

After I blew up enough guns in 2000, I learned what to look for in spotting a gun that is weaker than the brass. I have heavy bags full of parts from blowing up CZ52s and 38 special revolvers.

To relieve some of my extreme frustration with the lack of original source data transparency and repeatability of published load data, I wrote this essay:

""How to Write a Mediocre Load Book" Second revision""
http://groups.google.com/group/rec.g...2459399a2afb1d

But then we have been over this before:
http://thefiringline.com/forums/showthread.php?t=323723

I have since been frustrated with Denton Bramwell and his followers [lack of reasoning, purpose definition, and NIST traceable error calculation in pressure testing with strain gauges on guns stronger than the brass] internet posts.

[MR 8x57js]

It's not an exact science it's only a guide, so you have to do alot of research. As for OAL you will need to know at which OAL YOUR weapon work the best. variables render "data manuals' as guides ONLY.
The Alliant Manual starts 4.4 and Max's out 6.5 with a OAL at 1.260. With that as your base line you can work up a load that is to your specs. Uniqie is a great powder in the 45 ACP,good luck

[geetarman]

I do quite a lot of reloading and use most of the popular reloading manuals.

I do not know how the data in the manuals are collected. I am certainly no expert in the science of burn rates and energy. I am ONLY speaking of the ease with which data from a manual can be misinterpreted by not carefully looking at the shape and composition of the bullet for which you are loading.

While I do notice SOME variance in the data for loads, MOST of the variance comes from interpolating data from one SPECIFIC bullet type or shape to another. For example, if you get in a hurry, you might take the data for a .45 cal. 225 gr hard cast bullet when what you wanted was a 225 gr. half jacketed bullet. Close, but no cigar.

I have made the mistake and it is pretty easy to do, I never load to maximum velocities so sometimes I am disappointed with the results but not surprised with a whole lot of flame and noise.