Discrepencys between editions of Sierra manuals

[Matt_G]

I was just looking thru the new 5th edition of Sierra's manual I just bought and noticed some surprising changes from the previous 4th edition. (50th Anniversary Edition)

I have only looked at one caliber so far. 7mm-08
4th edition:
150gr MatchKing, IMR 4064 Powder:
Starting load is 36.1 grs. Vel 2300 fps
Max load is 42.1 grs. Vel is 2750 fps

5th Edition same bullet and powder:
Starting load is 35.1 grs. Vel 2400 fps
Max load is 39.5 grs. Vel is 2700 fps

Note that they dropped the max load by 2.6 grains!

4th Edition
168gr MatchKing, IMR 4064 Powder:
Starting load is 32.2 grs. Vel 2200 fps
Max load is 42.0 grs. Vel is 2700 fps

5th Edition same bullet and powder:
Starting load is 31.8 grs. Vel 2200 fps
Max load is 39.2 grs. Vel is 2600 fps

Again a big drop (2.8 grains) in the max load listed.

Does anyone have any ideas as to why Sierra has done this?
Here are my theories and I would like to hear what you think of them or put forth your own. /ubbthreads/images/graemlins/smile.gif

1) The data for the 5th edition was made using a different test barrel. Probably new and with tighter dimensions resulting in higher pressures for a given charge of powder.

2) When Hodgdon bought IMR in 2003 the burn rate of IMR 4064 powder changed somewaht due to different processes used. Since Hodgdon didn't buy IMR until October of 2003 and the 5th Edition of Sierras manual was published in 2003 I don't think this is the cause, but I could certainly be mistaken.

3) **** lawyers told them to knock back the charge weights due to our law suit crazy society, which was caused by **** lawyers in the first place. /ubbthreads/images/graemlins/crazy.gif

Note that they have knocked back the max charge weights on almost all powders for the 7-08, not just 4064, by a substantial margin.
Another note is that I just looked at some loads in .270 Win that I have used for quite a while and they do not seem to have changed at all.
Maybe theory #1 isn't that far off base.

 

[Guest]

You should have a read of my Speer reloading manual 1st edition. All the loads are hotter than my current manuals.

Because I see the more conservative loads across all powders, I'm guessing we blame the attorneys (or more accurately the outrageous product judgments that cause them to be so conservative). You other conjectures are interesting and may also be true.

 

[Matt_G]

Thanks for the response B1g_Bore.
I am leaning towards "lawyer loads" myself now.
Since I posted the original post I have done some more looking.
For instance I went to Alliants web site and they have max loads of Reloader 15 listed (7mm-08) using the Sierra 168 MatchKing that are 3-4 grains hotter than what Sierra has in their manuals. I'm going from memory here...

If this trend keeps up a Chronograph is going to become an absolutely necessary, instead of just a strongly recommended piece of equipment.

 

[Boss Hoss]

I always get a good laugh at the ole geezers who will proudly wave a 1973 manual and proclaim—your manual is no good just looky here and see for yourself the loads are WIMP Loads written by lawyers!! I just laugh and shake my head and go on—no use arguing with someone who suffers from dementia! Most have no idea that IMR 4350 manufactured in 1972 for the 1973 manual has very little in common with today's propellant—yes the burning rate may be similar but the old copper crusher method of measuring pressure has gone the way of the Edsel!! Just let them be ignorant in their ways and hope they don't kill themselves. /ubbthreads/images/graemlins/wink.gif

 

[captdavid]

I think that it is mostly due to the avalibility of relatively cheap pressure gauges. I read that at one time many companies 'shared/borrowed' data from each other, wheatere the other company gave permission or not. The also used stiky bolt flattend primers,&etc to set limits. Today it is easy to measure pressure. Every load is pressure checked and only relatively safe loads are recommended. John Barnsness did an article in HANDLOADER and said that some primers caused up to 5000-6000(I believe) pressure increases over others. If one loaded to the max with primer A and was at max pressure and changed, to that primer, it could get dangerous.My suggestion, buy a chrony and a pressure trace system, both for about the price of a decent scope, then you will know. just my $.02, capt david

 

[Matt_G]

[ QUOTE ]
My suggestion, buy a chrony and a pressure trace system, both for about the price of a decent scope, then you will know. just my $.02, capt david

[/ QUOTE ]
That is very good advice.

 

[Mikecr]

I say burn the reloading manuals. Pick up QuickLoad. It's the only reloading source with which you can calibrate for your barrel, lot of powder, seating, and powder temperature. Once calibrated to match velocities seen on my chrony, I've never seen it wrong(with that rifle).
I save a file for each of my rifles, and I can run 'what ifs' to my hearts content.

I love toys, but I can't see pressure trace on all my rifles. And I wonder about it's calibration(basis). SAAMI?
No, unless you have matching pressure test barrels, lots of powders, bullets?

 

[Guest]

A big Ahmen on QuickLOAD . As a Microsoft developer, I cringe at the horrible UI and other fundamental programming fopaux - but the results are excellent.

[ QUOTE ]
... but I can't see pressure trace on all my rifles. And I wonder about it's calibration(basis). SAAMI?

[/ QUOTE ]

I too am somewhat skeptical of PressureTrace, but that won't stop me from acquiring one and doing some testing. I think it's overkill for most folks. Like you say, a chrony, QL

captdavid does make an excellent point on primers (don't switch without starting load dev again). The PressureTrace looks pretty cool but is overkill for most folks.