Safety factor in reloading manuals?

[Thumper580]

Sort of curious about the max loads listed in the various reloading manuals. I know you can safely shoot them, does anyone know much safety factor is built into the max charge weights, 5%, 8%, 10%. Obviously it varies but an example would be informative.

 

[E. Bryant]

Any remaining safety factor in listed maximum loads is going to depend upon a boatload of variables, among the most significant being the mechanical properties of your particular firearm, the exact components used, and the environmental conditions at time a round is discharged. Therefore, it is impossible to state with any certainty the amount of safety factor that may exist with a stated load.

 

[Thumper580]

Any remaining safety factor in listed maximum loads is going to depend upon a boatload of variables, among the most significant being the mechanical properties of your particular firearm, the exact components used, and the environmental conditions at time a round is discharged. Therefore, it is impossible to state with any certainty the amount of safety factor that may exist with a stated load.

Maybe I didn't state my question well. Let's say Sierra lists a max charge of 44.0 grs of 4064 in their manual for a 175. Assuming a modern weapon in good condition, the 44grs is not a finite limit between safe and unsafe because we all know folks go abit higher than that. Curious what the actual level is that Sierra, or any other manufacturer, has determined is nearing the "unsafe" level. They must determine that and then back the level down by some percentage (lawyer required) and that is the amount that ends up in the reloading manual. Thanks.

 

[milo 2.0]

Thumper, there was a guy on here who said he was part of developing manuals and writing them. I can't recall offhand what he said, but I do remember it was substantial.
Not sure how old you are, but if you have access to older manuals, compare cartridge loads from old to new. They tone their data down quite often. So a load that was safe in 1985, might be over max today!

As for %, I have no way of knowing. But I can say, I like the Norma manual, and Norma powders, they are close to real world stats. Not sure if it's because it's Europe, instead of here????

 

[Asperly Aimless]

There is better pressure measuring equipment today than there was when alot of the older manuals were written.

 

[RTH1800]

Many of the older manuals were prepared without access to pressure data. Loads that had been reccomended for years were fount to be too hot. That is one reason data was backed off. Safety and fear of litigation are others.

It is best to work up data as the manual suggest. If you elect to go beyond that, be aware that tempature changes can really run up pressure. If you build your data on hot days allowing ammo to reach ambient temps prior to shooting, it will be fine in all weather.

If your primer pockets remain tight for 5-10 loadings, your pressure is fine. If not, consider backing load off until they stay tight.

If Kevin Thomas will comment on this, you will have the absolute last word on the subject.

 

[40xs]

I own probably 7-8 different loading manuals and all of them vary to some degree. some as much as 2-3 whole grains on the same rifle caliber. I'm certain a lot of it is due to protection against liability. I know there is a good deal of safety factored in due to the known working loads of most F-class shooters and what the manuals say is max. However, in the publisher's defense, we F-class shooters are getting very short case life and there is a definite reason for this, ie; We are using over max. loads!!! Always refer to your manual, especially in development of your load.

 

[jim_k]

rth1800 and 40xs posts above. All you need.
Jim

 

[jdonovan]

So I have 2 'modern' reloading manuals. < 10 years old.

In one manual the max load for a cartridge is less than the starting load for the same cartridge in another manual. Same powder and same projectile.

Some manuals list pressure of the loads in their test fixtures, and none of them exceed SAAMI, but some are very close... < 1000 psi from max.

From the sources I have gotten date from at powder companies, there is no safety factor in their numbers. When they list max loads, they were the max that did not exceed SAAMI specs' in their test rig.



There is a safety factor in the firearm.

European guns have to be shot with a proof cartridge at 25% above max CIP pressure, twice, and survive before being sold. SAAMI recommends 33-44% over pressure, but only requires 1 cartridge, AND SAAMI proof testing is optional, whereas CIP testing is mandatory.

 

[2Shots]

Unfortunately nobody knows the right answer. You are going to have to experiment your self under your conditions, rifle, powder batch, brand of case etc. Way to many variables involved to say a flat percentage. I as many others look at a book, ask questions on here or friends on their loads then start loading. I would typically on a new rifle start with my brass and bullet of choice and probably back off the max book load 5%, then depending on the results by checking the bolt lift, primer spread, typical pressure signs and adjust from there. I also like using a chrono early on also, lets me know if its shooting in the range I want with my choice of powders, accuracy though would be all new tests.

 

[Nukes]

I am holding in my hands a box of factory Hornady 140 gn AMAX in 6.5 Creedmoor. The box "recommends" 41.5 gn of H4350 for reloads. The 9th edition of the Hornady manual says 40.9 gn of H4350 is MAX for the same projectile.

 

[No1]

Safety factor?? I don't think any manufacturer in their right mind, who wants to stay out of litigation, is going to publish data that gives excess (beyond SAAMI) maximum average pressures in their test fixtures.
There is not "safety factor".

 

[turbo54]

SAAMI provides a maximum safe operating pressure.

Load data tells you what pressure was measured during test firing.

If you go higher than the manual suggests, you're almost certainly operating at higher-than-SAAMI-compliant pressure.

So the question is NOT if there is a safety factor in the load data - the question is what safety factor is designed/built into the brass, primers, bolt, action, etc etc

 

[Thumper580]

Good information. Thanks all. As mentioned above interesting how the same weight bullet and powder yield different max loads from one manufacturer to another. You would think they would yield very similar CIP results. Wasn't planning on shooting over max loads, but if used a load at max it isn't a few grains from destruction.

 

[witchhunter]

The manual states the pressure they detected in their test rifle using their components. Always work up to this data looking for pressure signs. The safety factor is in your interpretation of this data. Some of the powder recipes have changed slightly over the years, as they have changed ownership. Brass and chamber dimensions are subject to verification also.

 

[40xs]

Keep in mind that the publishers know that their suggested loads will at times be shot in guns that are 100 years old with varying chamber deminsions, etc. your manual is a starting guide. Use it as such and adjust as your conscience and common sense tells you and as others have said, know what the pressure signs are!!! The rest is on you!

 

[nso123]

One thing to consider too is that sometimes you may hit pressure signs before you get to the listed max load. I ran into this when I tried some AR-Comp in a load for a .308 bolt gun. I was a pretty good bit below the max load listed by Alliant. Like others have mentioned, there are factors beyond the powder that impact pressure. Some can get away with going beyond max listed loads with no visible signs of pressure, but that does not mean that they are not over pressure.