He certainly is correct about minor alterations of the load having influences on the load. His example especially with the small capacity case of his 'cat. I found that out a long time ago in '74 when I got my 1st Oehler chronograph with the 22 Hornet, 221 Rem and the 30 Carbine. With such small capacity cases, even in the 223 Rem, it is best to work powder charges up in .2 - .3 gr increments. The same in cartridges up through 30-30 capacity. In .308W or larger up through the "short" magnums .5 gr is a safe increment. Also changing bullets or primers can cause a major change as we have demonstrated with the tests in this thread.
New reloaders and those without chronographs are well suited to stay within published data from major manuals who actually test their data. Yes, I have pointed out one anomaly here in this thread but that's the only one I've found so far in the last 9 years since I began pressure testing. The data in the Hodgdon, Hornady, Speer, Lyman and Sierra manuals is pretty reliable.
Larry Gibson
“Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
― Nikola Tesla
Mr. Gibson thanks again for this post from your actual field research with the equipment most of us don't have ; as per out PMs I have backed off my loading of H4350 down to our agreed upon safe window ; the primer pockets on the brass and every aspect of the brass itself that has had 2 firings at what you determined to be potentially an over pressure charge is fine,but these were new cases. Funny thing in the new loading window I found two sweet loads that were not sweet loads during initial testing. The other thing I noted my chronographed velocity at the old near max charge weight was right on the heels of listed max, the new "max" as we discussed in PMs is a full 1.2 grains less and velocity is only slightly lower;70 -72 fps slower... now this is only with chronograph data on 10 of the old near max loads and 5 of the new near max with new Remington and Winchester cases H4350 powder Hornady 178-EDL-x in a ruger Mark 2 in 30-06 with cci benchrest 2 primers.
The new sweet spot that was not sweet the first time through produced a sub one inch 5 shot group exactly 2.8 inches high of poa at a known 102 yards.
The most accurate statement of pressure sign reading for any home reloader.
Reading primers for pressure is as accurate as reading tea leaves. By the time the physical pressure signs appear your already way over the SAAMI limit.
This reminds me of the story I read long ago in a gun magazine about the development of the wildcat 7mm STW. Handloads looks ok, but when lab pressure tested they were found to be to hot. And this was from an experienced handloader.
I read the the labs the collect data for loading manuals use the minimum spec pressure guns to get the pressure numbers, but the published velocity data is collected from real world off the shelf firearms.
So the MV would be more in line with what the home reloader would see.
Last edited by greenjoytj; 10-19-2017 at 09:05 AM. Reason: Spelling
Not all velocity data is collected from production guns. If one looks at several reloading data book one will see that.
3 Days ago Finally got around to loading Gordons Reloading Tool on my computer ...... think free Quick load software
Gordons Reloading Tool "GRT" is a software for handloaders and ammunition designers. It simulates combustion characteristics, pressures and bullet speeds through ballistic parameters and formulas.
when I started loading 300 aac Blackout One of my First outings , maybe the 2nd, I experienced expanded primer pockets,
Primers were on the flat side, but not to the extreme. just where you could push new primers in app 80% of the way in with your thumb. Not good
So I then, searched harder for data and did not use any data that was at the high end.
tried to use the lowest start published date as my starting loading charge
or used start data -5% as my start
I am sorry to say the maker of GTR has died so if you want/ need the software download it now ( you can make donations to keep GRT up on the www
Not sure if the other people working with GRT will/ do any updates in the future
I have spent the last 3 days entering loads that have worked and have not worked for me in the past ..... Like the above 300 BO load that had enlarged primer pockets
Some things I have found, you can save your work under different file names / folders ets
Comparing my Velocity data to GTR has been very close some times as close as 25-50fps
and in some instance finding out why i had the results I did have.
Like bad case sealing and dirty cases on start loads
to print them you have to do a Screen shot (control+Print screen)/ open and paste in a paint program and then you can print it
if anyone has a way to print from GRT let me know
What I have been doing is printing my data sheets on one side of the paper and data entered from GRT on the other side
No data for red dot or sr4759 and others
If you know how to add powders in to GRT, I would like to know
you can add your own Cast bullets .... added some NOE bullets to the my user database
you can change case volume H2O for example
you can change barrel length / weight etc
you need to change cast bullet data ie .311 Dia to .308 or you get a warning .... easy fix
GRT
has cast bullets under Lyman, lee so look around under different names ...... and find what you are looking for
using expert mode BTY
I spent a significant amount of time doing instrument caliibration and designing measurement systems. When I got into reloading, I was somewhat aghast at chamber pressure measurement techniques. I think the best you get is a halfway guess. It is my opinion that pressure measuring in shooting .
Closest recorded range Chrony kill (3 feet with witnesses)
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |