Re: H4895 w 155 Palmas
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RJ Hunter</div><div class="ubbcode-body">Read his advice on going over on charge weight. STUPID! Its ok though, I'm sure that after he blows himself up, his lawyers will give him better advice and sue the respondent. Get a loading manual and learn to read. </div></div>
RJ,
I guess this was directed to me?
Let me explain some stupidity to you. A max charge is what you actually develop in your rifle. Sometimes you hit MAX before the book or manual tells you. And sometimes you hit MAX above what the book or manual tells you.
Why? Because your rifle, it's barrel and chamber, and your powder lot, case, primers, et al is completely different than what was used in the book or manual.
Loads for books or manuals were developed based on recommended SAAMI pressures, as tested in their rifles.
Let look at some of these rounds:
243 WIN 60Kpsi
260 REM 60Kpsi
7mm-08 61Kpsi
308 Win 62k PSI
Is the brass substantially different in these rounds?
How about this set:
6mm Rem 65Kpsi
25-06 63Kpsi
270 Win 65Kpsi
Is the brass in a 6mm Rem built stronger than 243 brass? Or is 270 Win and any 30-06 parent brass made out of totally different materials than say 308 brass?
Remember most of these loads also have to work safely in levers, pump actions and autoloaders, not just strong modern bolt actions and single shots (like the Ruger #1).
The MAX loads listed by Hodgdon above are at 58200 PSI for IMR4895 (actual SAAMI Max of 62Kpsi) and 49700 CUP for H4895 (actual SAAMI Max 51400 CUP). So both MAX loads are in fact BELOW SAAMI Max for a 308.
Does than mean I suggest somebody start there loads there? No, I always recommend you start low at the MIN and work up to MAX. And you rifle will not self destruct if you happen to build some loads ABOVE book max, as long as you: work up carefully from below, and measure each case, look for all pressure signs, chronograph each load (velocity will tell you more about MAX, than studying your brass case will, since most cases will not begin to show pressure signs until well north of 65 K PSI), and have sound, modern firearm, and KNOW it's pressure limitations, based on it's design.
Let me ask you a question? What does a MAX load, as listed in a book or manual mean to you?
Is it:
A) A line you never ever cross?
B) A line you approach with caution?
C) Something else?
Here's a something else for you to ponder:
Hodgdon Data Manual #26
7mm Rem Mag
H1000 160 gr Bullet Min 71.0 Grains 2983 FPS 50300 CUP
H1000 160 Gr Bullet MAX 72.5 Grains 3038 FPS 52000 CUP
Hodgdon Data Manual #27
7mm Rem Mag
H1000 160 gr Bullet MIN 63.0 grains 2729 FPS 43300 CUP
H1000 160 Gr Bullet MAX 68.0 Grains 2839 FPS 49600 CUP
Today Hodgdon lists the H1000 MAX & 160 gr Nosler as 66 grains, 2839 FPS, and 49600 CUP. The exact same velocity and pressure they got with 68 grains. Did the powder change or is there data a bit of FUBAR?
(An aside: BTW SAMMI MAX for the 7mm Rem Mag is 61Kpsi or 50400 CUP. It used to be higher, but SAMMI has lowered the standard for this cartridge over the years.
The 7mm STW on the other hand, a larger capacity, but no stronger case than the 7mm Rem Mag, has SAAMI MAX's of 65Kpsi and 54200 CUP.
The real reason for the difference between the two cartidges has more to do with the chambers, their leads, and how they are designed by the many makers who chamber them, than the relative strength of the brass or of the rifles. Now back to the discussion.)
So which load is more dangerous? The MIN in Data Manual 26 or the MAX in data manual 27?
The correct answer is both or neither: because what you develop safely in your rifle (which may be higher or lower), trumps what is written in some book, and developed in a different rifle, with different powder lots......
Did my rifle self-dissemble itself after reading that my load compared to Data manual 27 was 3.8 grains above MAX published, and was developed under the rules of data manual 26, and I was using 71.8 Grains of H1000 and 160 Nosler Partition? Was it safe in my rifle and no others? Yes. Was I over the new book MAX? Yes. Did I lower my charge? NO.
I fired over 2k rounds from that rifle and barrel, and most were the exact same load. I wore that barrel out, and re-barreled. I'm now using a load 2 grains less. Not because the old load was dangerous, but because my new barrel and chamber develops near the same velocity, and better accuracy with 2 less grains of powder. Guess what, I'm still over the new book MAX by 3.8 grains....... Ponder that......
Regards,
Bob