Maximum Loads

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LabDan

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Hi ,
Why that maximum loads are different from book to book for the same bullet weight ( 70gr stay a 70gr , no matter what company ??? )
is it the max load that they tried or really the max load that you should use ?
What would be the main reasons for that difference ( gun , barrel lenght , brass inside volume or something else ... etc ... )
Ex.: .243 / 70gr. / Varget ... Sierra - 41.1 ... Nosler - 42.0 ... Hodgdon - 40.5
Thank you !
 
Yes - Results vary from load test at one facility to another, due to the variations you describe, including different manufacturers of bullets. For a given rifle owned by the public, max pressure can be realized at even lower powder charges. Thats why it is recommended that you work up from minimum load.
 
Consider also that the various manuals come to their data from different directions. Some will give you a maximum load with the corresponding velocity while others give you the maximum velocity with a corresponding load. Some provide data that was worked up and shot in a pressure barrel, others from an off the shelf firearm, and some data was simply mathematically determined without being shot. Sometimes published data is just wrong, the Hornady data for the .375 Ultra is a case in point and does not jive with the published data from any other source. For this reason I prefer to double check data that is unknown to me from a number of sources before I begin loading.
 
An extremely 338 WM load was not safe when temperatures exceeded 10 degrees C.
Bearing surface can make a difference say in a boattail versus a flat base.
 
That's why the other aside of the page says STARTING loads.;)

Cases in point - I have two rifles in .308 Winchester. One especially likes 44 gr. of IMR 4064 / 180 Nosler Partitions / WW brass / CCI-200 primers. With that particular rifle, I can easily go a full grain or even more over 'book max' on most loads before I see pressure signs.

The other shoots very well at 41 gr. (all other components being the same), gives equal velocity to the 44 gr. load in the first rifle, and shows pressure signs at anything ABOVE 41 gr.

Noslers manual lists the 44 gr. load as 'Maximum' for that bullet, but the second rifle will not accept that load safely. The first rifle can exceed it without generating unsafe pressures.

The only measurable difference that I can detect is that the latter rifle has a smaller chamber and a shorter throat, while the first one has a throat like Linda Lovelace.

Another case is an early-numbered (and wickedly accurate) Sako L61R in .338 W.M.; it gives full velocity with loads well under 'book' maximums....about midpoint between "starting" and "maximum" is all it will tolerate.

Now - the books, and their variations. Those books were complied at various times, with various test barrels and various batches and lot numbers of components. It cannot be said too loudly or too often to beginners - THOSE ARE GUIDELINES, NOT RECIPES! Your individual rifle is the final determining factor.
 
Tumbleweed
The only measurable difference that I can detect is that the latter rifle has a smaller chamber and a shorter throat, while the first one has a throat like Linda Lovelace.

aaahhhh.....Lovely Linda:D
 
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