Does anyone else get this moronic outcome in GRT?
- Thread starter marchx
- Start date
You know ... I got QuickLoad, tried Gordon's ... and other tools ... but I've learned through much experience that the fastest way to the perfect load, is to use one of the big database web sites (like Hodgdon), start with 10% below max charge weight, and build a ladder from there to find a flat spot, then shoot a bunch and enjoy the results. If I get pressure signs ... back off. If I don't, keep gradually increasing the charge until results match desires (low SD, tight groups, etc.). Haven't opened QL in a few years, and getting great results just by picking a well-published starting point, and laddering up from there.
Do you measure your actual fired case capacity? I've run into this issue a number of times where my cases hold a few percent more than the listed spec. I also have many instances of my powder lot being different enough that my velocity is quite a bit under what is expected. This is where you'd make adjustments in the obt section to match the numbers up to what your cases and powder lot are actually producing.
Murray Brook
Silver $$ Contributor
Both QL and GRT don't work that good unless all your specs are entered into the program and the burn rate factor of your powder is matched to a known velocity that you are getting with your present lot of powder. Only after all of this (IMO) can you get decent results....sometime.
Forget the computer programs. Just shoot the rifle and look at the targets. There is no such thing as flat spots. Try the powders used by top shooters in competition.
Orr89rocz
Silver $$ Contributor
I find it sometimes needs tweaking. But had been fairly accurate for other cartridges. Also you may have a fast barrel if its got enough rounds thru it to break in
Quickload gives 2720, and burn rate adjustment is needed to raise to near 2800 but pressure goes over 63000
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I agree. I've used GRT quite a bit. It is a really decent tool. Same with QL. They are only as good as the powder and cartridge data entered. There are so many variables that can affect the outcome it is best to not use it blindly. Most of the time I have used it, and a good ladder test, to determine the best barrel time/muzzle velocity for a given bullet, ie, find the nodes.
Can you get a decent tune without it? Of course you can. I've done it for decades, even without a chronograph as well. All you really need is a good range day or three
Not just QL and GRT. FWIW, I have a Savage BVSS originally in .308. Sierra used that same model for the data in their manual. I matched components and loads. Mine were almost 100fps different than theirs. Different lot number powder/primers/bullets/cases can make a difference, as well as a different temperature at the range on the day of the shoot.
Can you get a decent tune without it? Of course you can. I've done it for decades, even without a chronograph as well. All you really need is a good range day or three
Not just QL and GRT. FWIW, I have a Savage BVSS originally in .308. Sierra used that same model for the data in their manual. I matched components and loads. Mine were almost 100fps different than theirs. Different lot number powder/primers/bullets/cases can make a difference, as well as a different temperature at the range on the day of the shoot.
coldboreshot
Silver $$ Contributor
Sounds more like science fiction than science fact.
coldboreshot
Silver $$ Contributor
Some of us will be battling the A.I. uprising while the rest are still figuring out their load data on a computer.
It's a tool like any other. If you don't know how or care to learn how to use it, best to leave it on the wall.
I found that if I buy a premium barrel like, Brux, Broughton, Kreiger and have in chambered by a top gunsmith I can shoot almost any load under .400". Good enough for GH hunting.
DaveTooley
Gold $$ Contributor
FWIW VV has a burn rate tolerance of +/- 3%
jelenko
Gold $$ Contributor
I've used GRT for just 223 but for several years across 7 different powders and 8 different bullets.
I've always entered the measured bullet length, the actual H2O case capacity, the COAL and the temperature of the powder and entered the velocities from 7-8 shots.
The GRT OBT predicted node has always been within 2/10 grain.
The one kind of exception was the 62 eldt - it had to be seated right at the lands. At 2.340 it produced 6" patterns.
I've always entered the measured bullet length, the actual H2O case capacity, the COAL and the temperature of the powder and entered the velocities from 7-8 shots.
The GRT OBT predicted node has always been within 2/10 grain.
The one kind of exception was the 62 eldt - it had to be seated right at the lands. At 2.340 it produced 6" patterns.
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